Merge branch 'master' into topic/34716

.azure-pipelines/windows-release/stage-pack-msix.yml

@@ -120,10 +120,11 @@ jobs:
       artifactName: unsigned_msix
       downloadPath: $(Build.BinariesDirectory)
 
+  # MSIX must be signed and timestamped simultaneously
   - powershell: |
       $failed = $true
       foreach ($retry in 1..3) {
-          signtool sign /a /n "$(SigningCertificate)" /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d "$(SigningDescription)" (gi *.msix)
+          signtool sign /a /n "$(SigningCertificate)" /fd sha256 /tr http://timestamp.digicert.com/ /td sha256 /d "$(SigningDescription)" (gi *.msix)
           if ($?) {
               $failed = $false
               break

.azure-pipelines/windows-release/stage-pack-nuget.yml

@@ -4,7 +4,7 @@ jobs:
   condition: and(succeeded(), eq(variables['DoNuget'], 'true'))
 
   pool:
-    vmImage: windows-2019
+    name: 'Windows Release'
 
   workspace:
     clean: all
@@ -36,6 +36,14 @@ jobs:
       nuget pack "$(Build.BinariesDirectory)\layout\python.nuspec" -OutputDirectory $(Build.ArtifactStagingDirectory) -NoPackageAnalysis -NonInteractive
     displayName: 'Create nuget package'
 
+  - powershell: |
+      gci *.nupkg | %{
+        nuget sign "$_" -CertificateSubjectName "$(SigningCertificate)" -Timestamper http://timestamp.digicert.com/ -Overwrite
+      }
+    displayName: 'Sign nuget package'
+    workingDirectory: $(Build.ArtifactStagingDirectory)
+    condition: and(succeeded(), variables['SigningCertificate'])
+
   - task: PublishBuildArtifacts@1
     displayName: 'Publish Artifact: nuget'
     inputs:

.azure-pipelines/windows-release/stage-sign.yml

@@ -57,7 +57,7 @@ jobs:
       $files = (gi ${{ parameters.Include }} -Exclude ${{ parameters.Exclude }})
       $failed = $true
       foreach ($retry in 1..10) {
-          signtool timestamp /t http://timestamp.verisign.com/scripts/timestamp.dll $files
+          signtool timestamp /tr http://timestamp.digicert.com/ /td sha256 $files
           if ($?) {
               $failed = $false
               break

.github/dependabot.yml

@@ -0,0 +1,9 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    labels:
+      - "skip issue"
+      - "skip news"

.github/workflows/build.yml

@@ -106,7 +106,7 @@ jobs:
       run: sudo ./.github/workflows/posix-deps-apt.sh
     - name: 'Restore OpenSSL build'
       id: cache-openssl
-      uses: actions/cache@v1
+      uses: actions/cache@v2.1.2
       with:
         path: ./multissl/openssl/${{ env.OPENSSL_VER }}
         key: ${{ runner.os }}-multissl-openssl-${{ env.OPENSSL_VER }}

.github/workflows/coverage.yml

@@ -32,7 +32,7 @@ jobs:
       run: sudo ./.github/workflows/posix-deps-apt.sh
     - name: 'Restore OpenSSL build'
       id: cache-openssl
-      uses: actions/cache@v1
+      uses: actions/cache@v2.1.2
       with:
         path: ./multissl/openssl/${{ env.OPENSSL_VER }}
         key: ${{ runner.os }}-multissl-openssl-${{ env.OPENSSL_VER }}

.github/workflows/doc.yml

@@ -38,7 +38,7 @@ jobs:
     - name: 'Build documentation'
       run: xvfb-run make -C Doc/ PYTHON=../python SPHINXOPTS="-q -W --keep-going -j4" doctest suspicious html
     - name: 'Upload'
-      uses: actions/upload-artifact@v1
+      uses: actions/upload-artifact@v2.2.0
       with:
         name: doc-html
         path: Doc/build/html

.github/workflows/posix-deps-apt.sh

@@ -3,19 +3,19 @@ apt-get update
 
 apt-get -yq install \
     build-essential \
-    zlib1g-dev \
+    gdb \
+    lcov \
     libbz2-dev \
+    libffi-dev \
+    libgdbm-dev \
     liblzma-dev \
     libncurses5-dev \
     libreadline6-dev \
     libsqlite3-dev \
     libssl-dev \
-    libgdbm-dev \
-    tk-dev \
     lzma \
     lzma-dev \
-    liblzma-dev \
-    libffi-dev \
+    tk-dev \
     uuid-dev \
     xvfb \
-    lcov
+    zlib1g-dev

.gitignore

@@ -103,6 +103,8 @@ Tools/unicode/data/
 /config.status
 /config.status.lineno
 /platform
+/profile-clean-stamp
+/profile-run-stamp
 /pybuilddir.txt
 /pyconfig.h
 /python-config

Doc/Makefile

@@ -215,12 +215,12 @@ serve:
 
 # for development releases: always build
 autobuild-dev:
-	make dist SPHINXOPTS='$(SPHINXOPTS) -Ea -A daily=1 -A switchers=1'
+	make dist SPHINXOPTS='$(SPHINXOPTS) -Ea -A daily=1'
 	-make suspicious
 
 # for quick rebuilds (HTML only)
 autobuild-dev-html:
-	make html SPHINXOPTS='$(SPHINXOPTS) -Ea -A daily=1 -A switchers=1'
+	make html SPHINXOPTS='$(SPHINXOPTS) -Ea -A daily=1'
 
 # for stable releases: only build if not in pre-release stage (alpha, beta)
 # release candidate downloads are okay, since the stable tree can be in that stage

Doc/c-api/arg.rst

@@ -482,7 +482,8 @@ API Functions
    *min* and no more than *max*; *min* and *max* may be equal.  Additional
    arguments must be passed to the function, each of which should be a pointer to a
    :c:type:`PyObject*` variable; these will be filled in with the values from
-   *args*; they will contain borrowed references.  The variables which correspond
+   *args*; they will contain :term:`borrowed references <borrowed reference>`.
+   The variables which correspond
    to optional parameters not given by *args* will not be filled in; these should
    be initialized by the caller. This function returns true on success and false if
    *args* is not a tuple or contains the wrong number of elements; an exception

Doc/c-api/exceptions.rst

@@ -182,8 +182,8 @@ For convenience, some of these functions will always return a
 .. c:function:: PyObject* PyErr_SetFromErrnoWithFilename(PyObject *type, const char *filename)
 
    Similar to :c:func:`PyErr_SetFromErrnoWithFilenameObject`, but the filename
-   is given as a C string.  *filename* is decoded from the filesystem encoding
-   (:func:`os.fsdecode`).
+   is given as a C string.  *filename* is decoded from the :term:`filesystem
+   encoding and error handler`.
 
 
 .. c:function:: PyObject* PyErr_SetFromWindowsErr(int ierr)
@@ -266,7 +266,7 @@ For convenience, some of these functions will always return a
 .. c:function:: void PyErr_SyntaxLocationEx(const char *filename, int lineno, int col_offset)
 
    Like :c:func:`PyErr_SyntaxLocationObject`, but *filename* is a byte string
-   decoded from the filesystem encoding (:func:`os.fsdecode`).
+   decoded from the :term:`filesystem encoding and error handler`.
 
    .. versionadded:: 3.2
 
@@ -343,7 +343,7 @@ an error value).
 
    Similar to :c:func:`PyErr_WarnExplicitObject` except that *message* and
    *module* are UTF-8 encoded strings, and *filename* is decoded from the
-   filesystem encoding (:func:`os.fsdecode`).
+   :term:`filesystem encoding and error handler`.
 
 
 .. c:function:: int PyErr_WarnFormat(PyObject *category, Py_ssize_t stack_level, const char *format, ...)

Doc/c-api/init.rst

@@ -151,8 +151,9 @@ to 1 and ``-bb`` sets :c:data:`Py_BytesWarningFlag` to 2.
 
 .. c:var:: int Py_LegacyWindowsFSEncodingFlag
 
-   If the flag is non-zero, use the ``mbcs`` encoding instead of the UTF-8
-   encoding for the filesystem encoding.
+   If the flag is non-zero, use the ``mbcs`` encoding with ``replace`` error
+   handler, instead of the UTF-8 encoding with ``surrogatepass`` error handler,
+   for the :term:`filesystem encoding and error handler`.
 
    Set to ``1`` if the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment
    variable is set to a non-empty string.
@@ -1076,7 +1077,7 @@ All of the following functions must be called after :c:func:`Py_Initialize`.
 
    Get the current frame of the Python thread state *tstate*.
 
-   Return a strong reference. Return ``NULL`` if no frame is currently
+   Return a :term:`strong reference`. Return ``NULL`` if no frame is currently
    executing.
 
    See also :c:func:`PyEval_GetFrame`.

Doc/c-api/intro.rst

@@ -326,7 +326,7 @@ when it's no longer needed---or passing on this responsibility (usually to its
 caller). When a function passes ownership of a reference on to its caller, the
 caller is said to receive a *new* reference.  When no ownership is transferred,
 the caller is said to *borrow* the reference. Nothing needs to be done for a
-borrowed reference.
+:term:`borrowed reference`.
 
 Conversely, when a calling function passes in a reference to an  object, there
 are two possibilities: the function *steals* a  reference to the object, or it

Doc/c-api/module.rst

@@ -264,7 +264,7 @@ of the following two module creation functions:
       instead; only use this if you are sure you need it.
 
 Before it is returned from in the initialization function, the resulting module
-object is typically populated using functions like :c:func:`PyModule_AddObject`.
+object is typically populated using functions like :c:func:`PyModule_AddObjectRef`.
 
 .. _multi-phase-initialization:
 
@@ -437,26 +437,102 @@ a function called from a module execution slot (if using multi-phase
 initialization), can use the following functions to help initialize the module
 state:
 
+.. c:function:: int PyModule_AddObjectRef(PyObject *module, const char *name, PyObject *value)
+
+   Add an object to *module* as *name*.  This is a convenience function which
+   can be used from the module's initialization function.
+
+   On success, return ``0``. On error, raise an exception and return ``-1``.
+
+   Return ``NULL`` if *value* is ``NULL``. It must be called with an exception
+   raised in this case.
+
+   Example usage::
+
+       static int
+       add_spam(PyObject *module, int value)
+       {
+           PyObject *obj = PyLong_FromLong(value);
+           if (obj == NULL) {
+               return -1;
+           }
+           int res = PyModule_AddObjectRef(module, "spam", obj);
+           Py_DECREF(obj);
+           return res;
+        }
+
+   The example can also be written without checking explicitly if *obj* is
+   ``NULL``::
+
+       static int
+       add_spam(PyObject *module, int value)
+       {
+           PyObject *obj = PyLong_FromLong(value);
+           int res = PyModule_AddObjectRef(module, "spam", obj);
+           Py_XDECREF(obj);
+           return res;
+        }
+
+   Note that ``Py_XDECREF()`` should be used instead of ``Py_DECREF()`` in
+   this case, since *obj* can be ``NULL``.
+
+   .. versionadded:: 3.10
+
+
 .. c:function:: int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)
 
-   Add an object to *module* as *name*.  This is a convenience function which can
-   be used from the module's initialization function.  This steals a reference to
-   *value* on success. Return ``-1`` on error, ``0`` on success.
+   Similar to :c:func:`PyModule_AddObjectRef`, but steals a reference to
+   *value* on success (if it returns ``0``).
+
+   The new :c:func:`PyModule_AddObjectRef` function is recommended, since it is
+   easy to introduce reference leaks by misusing the
+   :c:func:`PyModule_AddObject` function.
 
    .. note::
 
-      Unlike other functions that steal references, ``PyModule_AddObject()`` only
-      decrements the reference count of *value* **on success**.
+      Unlike other functions that steal references, ``PyModule_AddObject()``
+      only decrements the reference count of *value* **on success**.
 
       This means that its return value must be checked, and calling code must
-      :c:func:`Py_DECREF` *value* manually on error. Example usage::
+      :c:func:`Py_DECREF` *value* manually on error.
+
+   Example usage::
+
+      static int
+      add_spam(PyObject *module, int value)
+      {
+          PyObject *obj = PyLong_FromLong(value);
+          if (obj == NULL) {
+              return -1;
+          }
+          if (PyModule_AddObject(module, "spam", obj) < 0) {
+              Py_DECREF(obj);
+              return -1;
+          }
+          // PyModule_AddObject() stole a reference to obj:
+          // Py_DECREF(obj) is not needed here
+          return 0;
+      }
+
+   The example can also be written without checking explicitly if *obj* is
+   ``NULL``::
+
+      static int
+      add_spam(PyObject *module, int value)
+      {
+          PyObject *obj = PyLong_FromLong(value);
+          if (PyModule_AddObject(module, "spam", obj) < 0) {
+              Py_XDECREF(obj);
+              return -1;
+          }
+          // PyModule_AddObject() stole a reference to obj:
+          // Py_DECREF(obj) is not needed here
+          return 0;
+      }
+
+   Note that ``Py_XDECREF()`` should be used instead of ``Py_DECREF()`` in
+   this case, since *obj* can be ``NULL``.
 
-         Py_INCREF(spam);
-         if (PyModule_AddObject(module, "spam", spam) < 0) {
-             Py_DECREF(module);
-             Py_DECREF(spam);
-             return NULL;
-         }
 
 .. c:function:: int PyModule_AddIntConstant(PyObject *module, const char *name, long value)
 

Doc/c-api/refcounting.rst

@@ -13,8 +13,14 @@ objects.
 
 .. c:function:: void Py_INCREF(PyObject *o)
 
-   Increment the reference count for object *o*.  The object must not be ``NULL``; if
-   you aren't sure that it isn't ``NULL``, use :c:func:`Py_XINCREF`.
+   Increment the reference count for object *o*.
+
+   This function is usually used to convert a :term:`borrowed reference` to a
+   :term:`strong reference` in-place. The :c:func:`Py_NewRef` function can be
+   used to create a new :term:`strong reference`.
+
+   The object must not be ``NULL``; if you aren't sure that it isn't
+   ``NULL``, use :c:func:`Py_XINCREF`.
 
 
 .. c:function:: void Py_XINCREF(PyObject *o)
@@ -22,13 +28,55 @@ objects.
    Increment the reference count for object *o*.  The object may be ``NULL``, in
    which case the macro has no effect.
 
+   See also :c:func:`Py_XNewRef`.
+
+
+.. c:function:: PyObject* Py_NewRef(PyObject *o)
+
+   Create a new :term:`strong reference` to an object: increment the reference
+   count of the object *o* and return the object *o*.
+
+   When the :term:`strong reference` is no longer needed, :c:func:`Py_DECREF`
+   should be called on it to decrement the object reference count.
+
+   The object *o* must not be ``NULL``; use :c:func:`Py_XNewRef` if *o* can be
+   ``NULL``.
+
+   For example::
+
+       Py_INCREF(obj);
+       self->attr = obj;
+
+   can be written as::
+
+       self->attr = Py_NewRef(obj);
+
+   See also :c:func:`Py_INCREF`.
+
+   .. versionadded:: 3.10
+
+
+.. c:function:: PyObject* Py_XNewRef(PyObject *o)
+
+   Similar to :c:func:`Py_NewRef`, but the object *o* can be NULL.
+
+   If the object *o* is ``NULL``, the function just returns ``NULL``.
+
+   .. versionadded:: 3.10
+
 
 .. c:function:: void Py_DECREF(PyObject *o)
 
-   Decrement the reference count for object *o*.  The object must not be ``NULL``; if
-   you aren't sure that it isn't ``NULL``, use :c:func:`Py_XDECREF`.  If the reference
-   count reaches zero, the object's type's deallocation function (which must not be
-   ``NULL``) is invoked.
+   Decrement the reference count for object *o*.
+
+   If the reference count reaches zero, the object's type's deallocation
+   function (which must not be ``NULL``) is invoked.
+
+   This function is usually used to delete a :term:`strong reference` before
+   exiting its scope.
+
+   The object must not be ``NULL``; if you aren't sure that it isn't ``NULL``,
+   use :c:func:`Py_XDECREF`.
 
    .. warning::
 

Doc/c-api/reflection.rst

@@ -35,7 +35,7 @@ Reflection
 
    Get the *frame* next outer frame.
 
-   Return a strong reference, or ``NULL`` if *frame* has no outer frame.
+   Return a :term:`strong reference`, or ``NULL`` if *frame* has no outer frame.
 
    *frame* must not be ``NULL``.
 
@@ -46,7 +46,7 @@ Reflection
 
    Get the *frame* code.
 
-   Return a strong reference.
+   Return a :term:`strong reference`.
 
    *frame* must not be ``NULL``. The result (frame code) cannot be ``NULL``.
 

Doc/c-api/structures.rst

@@ -66,7 +66,7 @@ the definition of all other Python objects.
 
    Get the type of the Python object *o*.
 
-   Return a borrowed reference.
+   Return a :term:`borrowed reference`.
 
    .. versionchanged:: 3.10
       :c:func:`Py_TYPE()` is changed to the inline static function.
@@ -263,10 +263,12 @@ There are these calling conventions:
    of :c:type:`PyObject*` values indicating the arguments and the third
    parameter is the number of arguments (the length of the array).
 
-   This is not part of the :ref:`limited API <stable>`.
-
    .. versionadded:: 3.7
 
+   .. versionchanged:: 3.10
+
+      ``METH_FASTCALL`` is now part of the stable ABI.
+
 
 .. data:: METH_FASTCALL | METH_KEYWORDS
 

Doc/c-api/sys.rst

@@ -118,22 +118,21 @@ Operating System Utilities
 
 .. c:function:: wchar_t* Py_DecodeLocale(const char* arg, size_t *size)
 
-   Decode a byte string from the locale encoding with the :ref:`surrogateescape
-   error handler <surrogateescape>`: undecodable bytes are decoded as
-   characters in range U+DC80..U+DCFF. If a byte sequence can be decoded as a
-   surrogate character, escape the bytes using the surrogateescape error
-   handler instead of decoding them.
+   .. warning::
+      This function should not be called directly: use the :c:type:`PyConfig`
+      API with the :c:func:`PyConfig_SetBytesString` function which ensures
+      that :ref:`Python is preinitialized <c-preinit>`.
 
-   Encoding, highest priority to lowest priority:
+      This function must not be called before :ref:`Python is preinitialized
+      <c-preinit>` and so that the LC_CTYPE locale is properly configured: see
+      the :c:func:`Py_PreInitialize` function.
 
-   * ``UTF-8`` on macOS, Android, and VxWorks;
-   * ``UTF-8`` on Windows if :c:data:`Py_LegacyWindowsFSEncodingFlag` is zero;
-   * ``UTF-8`` if the Python UTF-8 mode is enabled;
-   * ``ASCII`` if the ``LC_CTYPE`` locale is ``"C"``,
-     ``nl_langinfo(CODESET)`` returns the ``ASCII`` encoding (or an alias),
-     and :c:func:`mbstowcs` and :c:func:`wcstombs` functions uses the
-     ``ISO-8859-1`` encoding.
-   * the current locale encoding.
+   Decode a byte string from the :term:`filesystem encoding and error handler`.
+   If the error handler is :ref:`surrogateescape error handler
+   <surrogateescape>`, undecodable bytes are decoded as characters in range
+   U+DC80..U+DCFF; and if a byte sequence can be decoded as a surrogate
+   character, the bytes are escaped using the surrogateescape error handler
+   instead of decoding them.
 
    Return a pointer to a newly allocated wide character string, use
    :c:func:`PyMem_RawFree` to free the memory. If size is not ``NULL``, write
@@ -143,6 +142,10 @@ Operating System Utilities
    not ``NULL``, ``*size`` is set to ``(size_t)-1`` on memory error or set to
    ``(size_t)-2`` on decoding error.
 
+   The :term:`filesystem encoding and error handler` are selected by
+   :c:func:`PyConfig_Read`: see :c:member:`~PyConfig.filesystem_encoding` and
+   :c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
+
    Decoding errors should never happen, unless there is a bug in the C
    library.
 
@@ -157,7 +160,8 @@ Operating System Utilities
    .. versionadded:: 3.5
 
    .. versionchanged:: 3.7
-      The function now uses the UTF-8 encoding in the UTF-8 mode.
+      The function now uses the UTF-8 encoding in the :ref:`Python UTF-8 Mode
+      <utf8-mode>`.
 
    .. versionchanged:: 3.8
       The function now uses the UTF-8 encoding on Windows if
@@ -166,22 +170,10 @@ Operating System Utilities
 
 .. c:function:: char* Py_EncodeLocale(const wchar_t *text, size_t *error_pos)
 
-   Encode a wide character string to the locale encoding with the
-   :ref:`surrogateescape error handler <surrogateescape>`: surrogate characters
-   in the range U+DC80..U+DCFF are converted to bytes 0x80..0xFF.
-
-   Encoding, highest priority to lowest priority:
-
-   * ``UTF-8`` on macOS, Android, and VxWorks;
-   * ``UTF-8`` on Windows if :c:data:`Py_LegacyWindowsFSEncodingFlag` is zero;
-   * ``UTF-8`` if the Python UTF-8 mode is enabled;
-   * ``ASCII`` if the ``LC_CTYPE`` locale is ``"C"``,
-     ``nl_langinfo(CODESET)`` returns the ``ASCII`` encoding (or an alias),
-     and :c:func:`mbstowcs` and :c:func:`wcstombs` functions uses the
-     ``ISO-8859-1`` encoding.
-   * the current locale encoding.
-
-   The function uses the UTF-8 encoding in the Python UTF-8 mode.
+   Encode a wide character string to the :term:`filesystem encoding and error
+   handler`. If the error handler is :ref:`surrogateescape error handler
+   <surrogateescape>`, surrogate characters in the range U+DC80..U+DCFF are
+   converted to bytes 0x80..0xFF.
 
    Return a pointer to a newly allocated byte string, use :c:func:`PyMem_Free`
    to free the memory. Return ``NULL`` on encoding error or memory allocation
@@ -190,9 +182,18 @@ Operating System Utilities
    If error_pos is not ``NULL``, ``*error_pos`` is set to ``(size_t)-1`` on
    success,  or set to the index of the invalid character on encoding error.
 
+   The :term:`filesystem encoding and error handler` are selected by
+   :c:func:`PyConfig_Read`: see :c:member:`~PyConfig.filesystem_encoding` and
+   :c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
+
    Use the :c:func:`Py_DecodeLocale` function to decode the bytes string back
    to a wide character string.
 
+   .. warning::
+      This function must not be called before :ref:`Python is preinitialized
+      <c-preinit>` and so that the LC_CTYPE locale is properly configured: see
+      the :c:func:`Py_PreInitialize` function.
+
    .. seealso::
 
       The :c:func:`PyUnicode_EncodeFSDefault` and
@@ -201,7 +202,8 @@ Operating System Utilities
    .. versionadded:: 3.5
 
    .. versionchanged:: 3.7
-      The function now uses the UTF-8 encoding in the UTF-8 mode.
+      The function now uses the UTF-8 encoding in the :ref:`Python UTF-8 Mode
+      <utf8-mode>`.
 
    .. versionchanged:: 3.8
       The function now uses the UTF-8 encoding on Windows if

Doc/c-api/type.rst

@@ -169,6 +169,10 @@ The following functions and structs are used to create
 
    .. versionadded:: 3.9
 
+   .. versionchanged:: 3.10
+
+      The function now accepts NULL ``tp_doc`` slot.
+
 .. c:function:: PyObject* PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
 
    Equivalent to ``PyType_FromModuleAndSpec(NULL, spec, bases)``.
@@ -259,5 +263,3 @@ The following functions and structs are used to create
 
       The desired value of the slot. In most cases, this is a pointer
       to a function.
-
-      May not be ``NULL``.

Doc/c-api/typeobj.rst

@@ -1213,8 +1213,9 @@ and :c:type:`PyType_Type` effectively act as defaults.)
    :func:`~gc.get_referents` function will include it.
 
    .. warning::
-       When implementing :c:member:`~PyTypeObject.tp_traverse`, only the members
-       that the instance *owns* (by having strong references to them) must be
+       When implementing :c:member:`~PyTypeObject.tp_traverse`, only the
+       members that the instance *owns* (by having :term:`strong references
+       <strong reference>` to them) must be
        visited. For instance, if an object supports weak references via the
        :c:member:`~PyTypeObject.tp_weaklist` slot, the pointer supporting
        the linked list (what *tp_weaklist* points to) must **not** be

Doc/c-api/unicode.rst

@@ -783,7 +783,7 @@ system.
    :c:data:`Py_FileSystemDefaultEncoding` (the locale encoding read at
    Python startup).
 
-   This function ignores the Python UTF-8 mode.
+   This function ignores the :ref:`Python UTF-8 Mode <utf8-mode>`.
 
    .. seealso::
 
@@ -819,7 +819,7 @@ system.
    :c:data:`Py_FileSystemDefaultEncoding` (the locale encoding read at
    Python startup).
 
-   This function ignores the Python UTF-8 mode.
+   This function ignores the :ref:`Python UTF-8 Mode <utf8-mode>`.
 
    .. seealso::
 
@@ -878,8 +878,7 @@ conversion function:
 
 .. c:function:: PyObject* PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
 
-   Decode a string using :c:data:`Py_FileSystemDefaultEncoding` and the
-   :c:data:`Py_FileSystemDefaultEncodeErrors` error handler.
+   Decode a string from the :term:`filesystem encoding and error handler`.
 
    If :c:data:`Py_FileSystemDefaultEncoding` is not set, fall back to the
    locale encoding.
@@ -899,8 +898,8 @@ conversion function:
 
 .. c:function:: PyObject* PyUnicode_DecodeFSDefault(const char *s)
 
-   Decode a null-terminated string using :c:data:`Py_FileSystemDefaultEncoding`
-   and the :c:data:`Py_FileSystemDefaultEncodeErrors` error handler.
+   Decode a null-terminated string from the :term:`filesystem encoding and
+   error handler`.
 
    If :c:data:`Py_FileSystemDefaultEncoding` is not set, fall back to the
    locale encoding.

Doc/c-api/veryhigh.rst

@@ -112,9 +112,9 @@ the same library that the Python runtime is using.
 
    Similar to :c:func:`PyRun_SimpleStringFlags`, but the Python source code is read
    from *fp* instead of an in-memory string. *filename* should be the name of
-   the file, it is decoded from the filesystem encoding
-   (:func:`sys.getfilesystemencoding`).  If *closeit* is true, the file is
-   closed before PyRun_SimpleFileExFlags returns.
+   the file, it is decoded from :term:`filesystem encoding and error handler`.
+   If *closeit* is true, the file is closed before
+   ``PyRun_SimpleFileExFlags()`` returns.
 
    .. note::
       On Windows, *fp* should be opened as binary mode (e.g. ``fopen(filename, "rb")``).
@@ -132,7 +132,7 @@ the same library that the Python runtime is using.
    Read and execute a single statement from a file associated with an
    interactive device according to the *flags* argument.  The user will be
    prompted using ``sys.ps1`` and ``sys.ps2``.  *filename* is decoded from the
-   filesystem encoding (:func:`sys.getfilesystemencoding`).
+   :term:`filesystem encoding and error handler`.
 
    Returns ``0`` when the input was
    executed successfully, ``-1`` if there was an exception, or an error code
@@ -151,9 +151,8 @@ the same library that the Python runtime is using.
 
    Read and execute statements from a file associated with an interactive device
    until EOF is reached.  The user will be prompted using ``sys.ps1`` and
-   ``sys.ps2``.  *filename* is decoded from the filesystem encoding
-   (:func:`sys.getfilesystemencoding`).  Returns ``0`` at EOF or a negative
-   number upon failure.
+   ``sys.ps2``.  *filename* is decoded from the :term:`filesystem encoding and
+   error handler`.  Returns ``0`` at EOF or a negative number upon failure.
 
 
 .. c:var:: int (*PyOS_InputHook)(void)
@@ -206,8 +205,8 @@ the same library that the Python runtime is using.
    Parse Python source code from *str* using the start token *start* according to
    the *flags* argument.  The result can be used to create a code object which can
    be evaluated efficiently. This is useful if a code fragment must be evaluated
-   many times. *filename* is decoded from the filesystem encoding
-   (:func:`sys.getfilesystemencoding`).
+   many times. *filename* is decoded from the :term:`filesystem encoding and
+   error handler`.
 
 
 .. c:function:: struct _node* PyParser_SimpleParseFile(FILE *fp, const char *filename, int start)
@@ -262,7 +261,7 @@ the same library that the Python runtime is using.
 
    Similar to :c:func:`PyRun_StringFlags`, but the Python source code is read from
    *fp* instead of an in-memory string. *filename* should be the name of the file,
-   it is decoded from the filesystem encoding (:func:`sys.getfilesystemencoding`).
+   it is decoded from the :term:`filesystem encoding and error handler`.
    If *closeit* is true, the file is closed before :c:func:`PyRun_FileExFlags`
    returns.
 
@@ -301,7 +300,7 @@ the same library that the Python runtime is using.
 .. c:function:: PyObject* Py_CompileStringExFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags, int optimize)
 
    Like :c:func:`Py_CompileStringObject`, but *filename* is a byte string
-   decoded from the filesystem encoding (:func:`os.fsdecode`).
+   decoded from the :term:`filesystem encoding and error handler`.
 
    .. versionadded:: 3.2
 

Doc/c-api/weakref.rst

@@ -57,10 +57,10 @@ as much as it can.
 
    .. note::
 
-      This function returns a **borrowed reference** to the referenced object.
+      This function returns a :term:`borrowed reference` to the referenced object.
       This means that you should always call :c:func:`Py_INCREF` on the object
-      except if you know that it cannot be destroyed while you are still
-      using it.
+      except it cannot be destroyed before the last usage of the borrowed
+      reference.
 
 
 .. c:function:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)

Doc/data/refcounts.dat

@@ -3007,6 +3007,9 @@ Py_GetVersion:const char*:::
 Py_INCREF:void:::
 Py_INCREF:PyObject*:o:+1:
 
+Py_NewRef:void:::
+Py_NewRef:PyObject*:o:+1:
+
 Py_Initialize:void:::
 
 Py_IsInitialized:int:::
@@ -3028,6 +3031,9 @@ Py_XDECREF:PyObject*:o:-1:if o is not NULL
 Py_XINCREF:void:::
 Py_XINCREF:PyObject*:o:+1:if o is not NULL
 
+Py_XNewRef:void:::
+Py_XNewRef:PyObject*:o:+1:if o is not NULL
+
 _PyImport_Fini:void:::
 
 _PyObject_New:PyObject*::+1:

Doc/glossary.rst

@@ -158,6 +158,18 @@ Glossary
       See also :term:`text file` for a file object able to read and write
       :class:`str` objects.
 
+   borrowed reference
+      In the Python's C API, a borrowed reference is a reference to an object.
+      It does not modify the object reference count. It becomes a dangling
+      pointer if the object is destroyed. For example, a garbage collection can
+      remove the last :term:`strong reference` to the object and so destroy it.
+
+      Calling :c:func:`Py_INCREF` on the :term:`borrowed reference` is
+      recommended to convert it to a :term:`strong reference` in-place, except
+      if the object cannot be destroyed before the last usage of the borrowed
+      reference. The :c:func:`Py_NewRef` function can be used to create a new
+      :term:`strong reference`.
+
    bytes-like object
       An object that supports the :ref:`bufferobjects` and can
       export a C-:term:`contiguous` buffer. This includes all :class:`bytes`,
@@ -301,7 +313,8 @@ Glossary
       including functions, methods, properties, class methods, static methods,
       and reference to super classes.
 
-      For more information about descriptors' methods, see :ref:`descriptors`.
+      For more information about descriptors' methods, see :ref:`descriptors`
+      or the :ref:`Descriptor How To Guide <descriptorhowto>`.
 
    dictionary
       An associative array, where arbitrary keys are mapped to values.  The
@@ -385,6 +398,25 @@ Glossary
    file-like object
       A synonym for :term:`file object`.
 
+   filesystem encoding and error handler
+      Encoding and error handler used by Python to decode bytes from the
+      operating system and encode Unicode to the operating system.
+
+      The filesystem encoding must guarantee to successfully decode all bytes
+      below 128. If the file system encoding fails to provide this guarantee,
+      API functions can raise :exc:`UnicodeError`.
+
+      The :func:`sys.getfilesystemencoding` and
+      :func:`sys.getfilesystemencodeerrors` functions can be used to get the
+      filesystem encoding and error handler.
+
+      The :term:`filesystem encoding and error handler` are configured at
+      Python startup by the :c:func:`PyConfig_Read` function: see
+      :c:member:`~PyConfig.filesystem_encoding` and
+      :c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
+
+      See also the :term:`locale encoding`.
+
    finder
       An object that tries to find the :term:`loader` for a module that is
       being imported.
@@ -482,6 +514,13 @@ Glossary
       See also the :term:`single dispatch` glossary entry, the
       :func:`functools.singledispatch` decorator, and :pep:`443`.
 
+   generic type
+      A :term:`type` that can be parameterized; typically a container like
+      :class:`list`. Used for :term:`type hints <type hint>` and
+      :term:`annotations <annotation>`.
+
+      See :pep:`483` for more details, and :mod:`typing` or
+      :ref:`generic alias type <types-genericalias>` for its uses.
 
    GIL
       See :term:`global interpreter lock`.
@@ -665,6 +704,18 @@ Glossary
       thread removes *key* from *mapping* after the test, but before the lookup.
       This issue can be solved with locks or by using the EAFP approach.
 
+   locale encoding
+      On Unix, it is the encoding of the LC_CTYPE locale. It can be set with
+      ``locale.setlocale(locale.LC_CTYPE, new_locale)``.
+
+      On Windows, it is is the ANSI code page (ex: ``cp1252``).
+
+      ``locale.getpreferredencoding(False)`` can be used to get the locale
+      encoding.
+
+      Python uses the :term:`filesystem encoding and error handler` to convert
+      between Unicode filenames and bytes filenames.
+
    list
       A built-in Python :term:`sequence`.  Despite its name it is more akin
       to an array in other languages than to a linked list since access to
@@ -1030,7 +1081,7 @@ Glossary
       :meth:`index`, :meth:`__contains__`, and
       :meth:`__reversed__`. Types that implement this expanded
       interface can be registered explicitly using
-      :func:`~abc.register`.
+      :func:`~abc.ABCMeta.register`.
 
    set comprehension
       A compact way to process all or part of the elements in an iterable and
@@ -1061,6 +1112,18 @@ Glossary
       an :term:`expression` or one of several constructs with a keyword, such
       as :keyword:`if`, :keyword:`while` or :keyword:`for`.
 
+   strong reference
+      In the Python's C API, a strong reference is a reference to an object
+      which increments object reference count when it is created and
+      decrements the object reference count when it is deleted.
+
+      The :c:func:`Py_NewRef` function can be used to create a strong reference
+      to an object. Usually, the :c:func:`Py_DECREF` function must be called on
+      the strong reference before exiting the scope of the strong reference, to
+      avoid leaking one reference.
+
+      See also :term:`borrowed reference`.
+
    text encoding
       A codec which encodes Unicode strings to bytes.
 

Doc/howto/unicode.rst

@@ -609,9 +609,9 @@ implemented by converting the Unicode string into some encoding that
 varies depending on the system.  Today Python is converging on using
 UTF-8: Python on MacOS has used UTF-8 for several versions, and Python
 3.6 switched to using UTF-8 on Windows as well.  On Unix systems,
-there will only be a filesystem encoding if you've set the ``LANG`` or
-``LC_CTYPE`` environment variables; if you haven't, the default
-encoding is again UTF-8.
+there will only be a :term:`filesystem encoding <filesystem encoding and error
+handler>`. if you've set the ``LANG`` or ``LC_CTYPE`` environment variables; if
+you haven't, the default encoding is again UTF-8.
 
 The :func:`sys.getfilesystemencoding` function returns the encoding to use on
 your current system, in case you want to do the encoding manually, but there's
@@ -633,8 +633,8 @@ provided the directory path as bytes or a Unicode string.  If you pass a
 Unicode string as the path, filenames will be decoded using the filesystem's
 encoding and a list of Unicode strings will be returned, while passing a byte
 path will return the filenames as bytes.  For example,
-assuming the default filesystem encoding is UTF-8, running the following
-program::
+assuming the default :term:`filesystem encoding <filesystem encoding and error
+handler>` is UTF-8, running the following program::
 
    fn = 'filename\u4500abc'
    f = open(fn, 'w')

Doc/library/ast.rst

@@ -80,12 +80,13 @@ Node classes
                   end_col_offset
 
       Instances of :class:`ast.expr` and :class:`ast.stmt` subclasses have
-      :attr:`lineno`, :attr:`col_offset`, :attr:`lineno`, and :attr:`col_offset`
-      attributes.  The :attr:`lineno` and :attr:`end_lineno` are the first and
-      last line numbers of source text span (1-indexed so the first line is line 1)
-      and the :attr:`col_offset` and :attr:`end_col_offset` are the corresponding
-      UTF-8 byte offsets of the first and last tokens that generated the node.
-      The UTF-8 offset is recorded because the parser uses UTF-8 internally.
+      :attr:`lineno`, :attr:`col_offset`, :attr:`end_lineno`, and
+      :attr:`end_col_offset` attributes.  The :attr:`lineno` and :attr:`end_lineno`
+      are the first and last line numbers of source text span (1-indexed so the
+      first line is line 1) and the :attr:`col_offset` and :attr:`end_col_offset`
+      are the corresponding UTF-8 byte offsets of the first and last tokens that
+      generated the node. The UTF-8 offset is recorded because the parser uses
+      UTF-8 internally.
 
       Note that the end positions are not required by the compiler and are
       therefore optional. The end offset is *after* the last symbol, for example

Doc/library/asyncio-task.rst

@@ -504,10 +504,10 @@ Waiting Primitives
                             return_when=ALL_COMPLETED)
 
    Run :ref:`awaitable objects <asyncio-awaitables>` in the *aws*
-   set concurrently and block until the condition specified
+   iterable concurrently and block until the condition specified
    by *return_when*.
 
-   The *aws* set must not be empty.
+   The *aws* iterable must not be empty.
 
    Returns two sets of Tasks/Futures: ``(done, pending)``.
 
@@ -593,9 +593,9 @@ Waiting Primitives
 .. function:: as_completed(aws, \*, loop=None, timeout=None)
 
    Run :ref:`awaitable objects <asyncio-awaitables>` in the *aws*
-   set concurrently.  Return an iterator of coroutines.
+   iterable concurrently.  Return an iterator of coroutines.
    Each coroutine returned can be awaited to get the earliest next
-   result from the set of the remaining awaitables.
+   result from the iterable of the remaining awaitables.
 
    Raises :exc:`asyncio.TimeoutError` if the timeout occurs before
    all Futures are done.

Doc/library/concurrent.futures.rst

@@ -236,9 +236,9 @@ to a :class:`ProcessPoolExecutor` will result in deadlock.
    An :class:`Executor` subclass that executes calls asynchronously using a pool
    of at most *max_workers* processes.  If *max_workers* is ``None`` or not
    given, it will default to the number of processors on the machine.
-   If *max_workers* is lower or equal to ``0``, then a :exc:`ValueError`
+   If *max_workers* is less than or equal to ``0``, then a :exc:`ValueError`
    will be raised.
-   On Windows, *max_workers* must be equal or lower than ``61``. If it is not
+   On Windows, *max_workers* must be less than or equal to ``61``. If it is not
    then :exc:`ValueError` will be raised. If *max_workers* is ``None``, then
    the default chosen will be at most ``61``, even if more processors are
    available.
@@ -250,7 +250,7 @@ to a :class:`ProcessPoolExecutor` will result in deadlock.
    each worker process; *initargs* is a tuple of arguments passed to the
    initializer.  Should *initializer* raise an exception, all currently
    pending jobs will raise a :exc:`~concurrent.futures.process.BrokenProcessPool`,
-   as well any attempt to submit more jobs to the pool.
+   as well as any attempt to submit more jobs to the pool.
 
    .. versionchanged:: 3.3
       When one of the worker processes terminates abruptly, a

Doc/library/contextlib.rst

@@ -126,6 +126,31 @@ Functions and classes provided:
 
    .. versionadded:: 3.7
 
+   Context managers defined with :func:`asynccontextmanager` can be used
+   either as decorators or with :keyword:`async with` statements::
+
+     import time
+
+     async def timeit():
+         now = time.monotonic()
+         try:
+             yield
+         finally:
+             print(f'it took {time.monotonic() - now}s to run')
+
+      @timeit()
+      async def main():
+          # ... async code ...
+
+   When used as a decorator, a new generator instance is implicitly created on
+   each function call. This allows the otherwise "one-shot" context managers
+   created by :func:`asynccontextmanager` to meet the requirement that context
+   managers support multiple invocations in order to be used as decorators.
+
+  .. versionchanged:: 3.10
+     Async context managers created with :func:`asynccontextmanager` can
+     be used as decorators.
+
 
 .. function:: closing(thing)
 
@@ -154,6 +179,39 @@ Functions and classes provided:
    ``page.close()`` will be called when the :keyword:`with` block is exited.
 
 
+.. class:: aclosing(thing)
+
+   Return an async context manager that calls the ``aclose()`` method of *thing*
+   upon completion of the block.  This is basically equivalent to::
+
+      from contextlib import asynccontextmanager
+
+      @asynccontextmanager
+      async def aclosing(thing):
+          try:
+              yield thing
+          finally:
+              await thing.aclose()
+
+   Significantly, ``aclosing()`` supports deterministic cleanup of async
+   generators when they happen to exit early by :keyword:`break` or an
+   exception.  For example::
+
+      from contextlib import aclosing
+
+      async with aclosing(my_generator()) as values:
+          async for value in values:
+              if value == 42:
+                  break
+
+   This pattern ensures that the generator's async exit code is executed in
+   the same context as its iterations (so that exceptions and context
+   variables work as expected, and the exit code isn't run after the
+   lifetime of some task it depends on).
+
+   .. versionadded:: 3.10
+
+
 .. _simplifying-support-for-single-optional-context-managers:
 
 .. function:: nullcontext(enter_result=None)
@@ -185,8 +243,26 @@ Functions and classes provided:
           with cm as file:
               # Perform processing on the file
 
+   It can also be used as a stand-in for
+   :ref:`asynchronous context managers <async-context-managers>`::
+
+       async def send_http(session=None):
+          if not session:
+              # If no http session, create it with aiohttp
+              cm = aiohttp.ClientSession()
+          else:
+              # Caller is responsible for closing the session
+              cm = nullcontext(session)
+
+          async with cm as session:
+              # Send http requests with session
+
    .. versionadded:: 3.7
 
+   .. versionchanged:: 3.10
+      :term:`asynchronous context manager` support was added.
+
+
 
 .. function:: suppress(*exceptions)
 
@@ -351,6 +427,45 @@ Functions and classes provided:
    .. versionadded:: 3.2
 
 
+.. class:: AsyncContextDecorator
+
+   Similar to :class:`ContextDecorator` but only for asynchronous functions.
+
+   Example of ``AsyncContextDecorator``::
+
+      from asyncio import run
+      from contextlib import AsyncContextDecorator
+
+      class mycontext(AsyncContextDecorator):
+          async def __aenter__(self):
+              print('Starting')
+              return self
+
+          async def __aexit__(self, *exc):
+              print('Finishing')
+              return False
+
+      >>> @mycontext()
+      ... async def function():
+      ...     print('The bit in the middle')
+      ...
+      >>> run(function())
+      Starting
+      The bit in the middle
+      Finishing
+
+      >>> async def function():
+      ...    async with mycontext():
+      ...         print('The bit in the middle')
+      ...
+      >>> run(function())
+      Starting
+      The bit in the middle
+      Finishing
+
+   .. versionadded:: 3.10
+
+
 .. class:: ExitStack()
 
    A context manager that is designed to make it easy to programmatically

Doc/library/devmode.rst

@@ -93,6 +93,9 @@ The Python Development Mode does not prevent the :option:`-O` command line
 option from removing :keyword:`assert` statements nor from setting
 :const:`__debug__` to ``False``.
 
+The Python Development Mode can only be enabled at the Python startup. Its
+value can be read from :data:`sys.flags.dev_mode <sys.flags>`.
+
 .. versionchanged:: 3.8
    The :class:`io.IOBase` destructor now logs ``close()`` exceptions.
 

Doc/library/email.errors.rst

@@ -112,3 +112,6 @@ All defect classes are subclassed from :class:`email.errors.MessageDefect`.
 * :class:`InvalidBase64LengthDefect` -- When decoding a block of base64 encoded
   bytes, the number of non-padding base64 characters was invalid (1 more than
   a multiple of 4).  The encoded block was kept as-is.
+
+* :class:`InvalidDateDefect` -- When decoding an invalid or unparsable date field.
+  The original value is kept as-is.

Doc/library/email.utils.rst

@@ -124,8 +124,10 @@ of the new API.
 .. function:: parsedate_to_datetime(date)
 
    The inverse of :func:`format_datetime`.  Performs the same function as
-   :func:`parsedate`, but on success returns a :mod:`~datetime.datetime`.  If
-   the input date has a timezone of ``-0000``, the ``datetime`` will be a naive
+   :func:`parsedate`, but on success returns a :mod:`~datetime.datetime`;
+   otherwise ``ValueError`` is raised if *date* contains an invalid value such
+   as an hour greater than 23 or a timezone offset not between -24 and 24 hours.
+   If the input date has a timezone of ``-0000``, the ``datetime`` will be a naive
    ``datetime``, and if the date is conforming to the RFCs it will represent a
    time in UTC but with no indication of the actual source timezone of the
    message the date comes from.  If the input date has any other valid timezone

Doc/library/exceptions.rst

@@ -313,8 +313,8 @@ The following exceptions are the exceptions that are usually raised.
    .. versionchanged:: 3.4
       The :attr:`filename` attribute is now the original file name passed to
       the function, instead of the name encoded to or decoded from the
-      filesystem encoding.  Also, the *filename2* constructor argument and
-      attribute was added.
+      :term:`filesystem encoding and error handler`. Also, the *filename2*
+      constructor argument and attribute was added.
 
 
 .. exception:: OverflowError

Doc/library/functions.rst

@@ -164,8 +164,8 @@ are always available.  They are listed here in alphabetical order.
    * If it is an *integer*, the array will have that size and will be
      initialized with null bytes.
 
-   * If it is an object conforming to the *buffer* interface, a read-only buffer
-     of the object will be used to initialize the bytes array.
+   * If it is an object conforming to the :ref:`buffer interface <bufferobjects>`,
+     a read-only buffer of the object will be used to initialize the bytes array.
 
    * If it is an *iterable*, it must be an iterable of integers in the range
      ``0 <= x < 256``, which are used as the initial contents of the array.
@@ -259,7 +259,7 @@ are always available.  They are listed here in alphabetical order.
    interactive statement (in the latter case, expression statements that
    evaluate to something other than ``None`` will be printed).
 
-   The optional argument *flags* and *dont_inherit* controls which
+   The optional arguments *flags* and *dont_inherit* control which
    :ref:`compiler options <ast-compiler-flags>` should be activated
    and which :ref:`future features <future>` should be allowed. If neither
    is present (or both are zero) the code is compiled with the same flags that

Doc/library/functools.rst

@@ -73,17 +73,32 @@ The :mod:`functools` module defines the following functions:
            def variance(self):
                return statistics.variance(self._data)
 
+   Note, this decorator interferes with the operation of :pep:`412`
+   key-sharing dictionaries.  This means that instance dictionaries
+   can take more space than usual.
+
+   Also, this decorator requires that the ``__dict__`` attribute on each instance
+   be a mutable mapping. This means it will not work with some types, such as
+   metaclasses (since the ``__dict__`` attributes on type instances are
+   read-only proxies for the class namespace), and those that specify
+   ``__slots__`` without including ``__dict__`` as one of the defined slots
+   (as such classes don't provide a ``__dict__`` attribute at all).
+
+   If a mutable mapping is not available or if space-efficient key sharing
+   is desired, an effect similar to :func:`cached_property` can be achieved
+   by a stacking :func:`property` on top of :func:`cache`::
+
+       class DataSet:
+           def __init__(self, sequence_of_numbers):
+               self._data = sequence_of_numbers
+
+           @property
+           @cache
+           def stdev(self):
+               return statistics.stdev(self._data)
+
    .. versionadded:: 3.8
 
-   .. note::
-
-      This decorator requires that the ``__dict__`` attribute on each instance
-      be a mutable mapping. This means it will not work with some types, such as
-      metaclasses (since the ``__dict__`` attributes on type instances are
-      read-only proxies for the class namespace), and those that specify
-      ``__slots__`` without including ``__dict__`` as one of the defined slots
-      (as such classes don't provide a ``__dict__`` attribute at all).
-
 
 .. function:: cmp_to_key(func)
 

Doc/library/ipaddress.rst

@@ -202,6 +202,32 @@ write code that handles both IP versions correctly.  Address objects are
 .. _iana-ipv4-special-registry: https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml
 .. _iana-ipv6-special-registry: https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml
 
+.. method:: IPv4Address.__format__(fmt)
+
+   Returns a string representation of the IP address, controlled by
+   an explicit format string.
+   *fmt* can be one of the following: ``'s'``, the default option,
+   equivalent to :func:`str`, ``'b'`` for a zero-padded binary string,
+   ``'X'`` or ``'x'`` for an uppercase or lowercase hexadecimal
+   representation, or ``'n'``, which is equivalent to ``'b'`` for IPv4
+   addresses and ``'x'`` for IPv6. For binary and hexadecimal
+   representations, the form specifier ``'#'`` and the grouping option
+   ``'_'`` are available. ``__format__`` is used by ``format``, ``str.format``
+   and f-strings.
+
+      >>> format(ipaddress.IPv4Address('192.168.0.1'))
+      '192.168.0.1'
+      >>> '{:#b}'.format(ipaddress.IPv4Address('192.168.0.1'))
+      '0b11000000101010000000000000000001'
+      >>> f'{ipaddress.IPv6Address("2001:db8::1000"):s}'
+      '2001:db8::1000'
+      >>> format(ipaddress.IPv6Address('2001:db8::1000'), '_X')
+      '2001_0DB8_0000_0000_0000_0000_0000_1000'
+      >>> '{:#_n}'.format(ipaddress.IPv6Address('2001:db8::1000'))
+      '0x2001_0db8_0000_0000_0000_0000_0000_1000'
+
+   .. versionadded:: 3.9
+
 
 .. class:: IPv6Address(address)
 
@@ -246,8 +272,8 @@ write code that handles both IP versions correctly.  Address objects are
    groups consisting entirely of zeroes included.
 
 
-   For the following attributes, see the corresponding documentation of the
-   :class:`IPv4Address` class:
+   For the following attributes and methods, see the corresponding
+   documentation of the :class:`IPv4Address` class:
 
    .. attribute:: packed
    .. attribute:: reverse_pointer
@@ -297,6 +323,12 @@ write code that handles both IP versions correctly.  Address objects are
       the embedded ``(server, client)`` IP address pair.  For any other
       address, this property will be ``None``.
 
+.. method:: IPv6Address.__format__(fmt)
+
+   Refer to the corresponding method documentation in
+   :class:`IPv4Address`.
+
+   .. versionadded:: 3.9
 
 Conversion to Strings and Integers
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Doc/library/locale.rst

@@ -315,21 +315,25 @@ The :mod:`locale` module defines the following exception and functions:
 
 .. function:: getpreferredencoding(do_setlocale=True)
 
-   Return the encoding used for text data, according to user preferences.  User
-   preferences are expressed differently on different systems, and might not be
-   available programmatically on some systems, so this function only returns a
-   guess.
+   Return the :term:`locale encoding` used for text data, according to user
+   preferences.  User preferences are expressed differently on different
+   systems, and might not be available programmatically on some systems, so
+   this function only returns a guess.
 
-   On some systems, it is necessary to invoke :func:`setlocale` to obtain the user
-   preferences, so this function is not thread-safe. If invoking setlocale is not
-   necessary or desired, *do_setlocale* should be set to ``False``.
+   On some systems, it is necessary to invoke :func:`setlocale` to obtain the
+   user preferences, so this function is not thread-safe. If invoking setlocale
+   is not necessary or desired, *do_setlocale* should be set to ``False``.
 
-   On Android or in the UTF-8 mode (:option:`-X` ``utf8`` option), always
-   return ``'UTF-8'``, the locale and the *do_setlocale* argument are ignored.
+   On Android or if the :ref:`Python UTF-8 Mode <utf8-mode>` is enabled, always
+   return ``'UTF-8'``, the :term:`locale encoding` and the *do_setlocale*
+   argument are ignored.
+
+   The :ref:`Python preinitialization <c-preinit>` configures the LC_CTYPE
+   locale. See also the :term:`filesystem encoding and error handler`.
 
    .. versionchanged:: 3.7
-      The function now always returns ``UTF-8`` on Android or if the UTF-8 mode
-      is enabled.
+      The function now always returns ``UTF-8`` on Android or if the
+      :ref:`Python UTF-8 Mode <utf8-mode>` is enabled.
 
 
 .. function:: normalize(localename)

Doc/library/os.rst

@@ -68,8 +68,13 @@ File Names, Command Line Arguments, and Environment Variables
 In Python, file names, command line arguments, and environment variables are
 represented using the string type. On some systems, decoding these strings to
 and from bytes is necessary before passing them to the operating system. Python
-uses the file system encoding to perform this conversion (see
-:func:`sys.getfilesystemencoding`).
+uses the :term:`filesystem encoding and error handler` to perform this
+conversion (see :func:`sys.getfilesystemencoding`).
+
+The :term:`filesystem encoding and error handler` are configured at Python
+startup by the :c:func:`PyConfig_Read` function: see
+:c:member:`~PyConfig.filesystem_encoding` and
+:c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
 
 .. versionchanged:: 3.1
    On some systems, conversion using the file system encoding may fail. In this
@@ -79,9 +84,72 @@ uses the file system encoding to perform this conversion (see
    original byte on encoding.
 
 
-The file system encoding must guarantee to successfully decode all bytes
-below 128. If the file system encoding fails to provide this guarantee, API
-functions may raise UnicodeErrors.
+The :term:`file system encoding <filesystem encoding and error handler>` must
+guarantee to successfully decode all bytes below 128. If the file system
+encoding fails to provide this guarantee, API functions can raise
+:exc:`UnicodeError`.
+
+See also the :term:`locale encoding`.
+
+
+.. _utf8-mode:
+
+Python UTF-8 Mode
+-----------------
+
+.. versionadded:: 3.7
+   See :pep:`540` for more details.
+
+The Python UTF-8 Mode ignores the :term:`locale encoding` and forces the usage
+of the UTF-8 encoding:
+
+* Use UTF-8 as the :term:`filesystem encoding <filesystem encoding and error
+  handler>`.
+* :func:`sys.getfilesystemencoding()` returns ``'UTF-8'``.
+* :func:`locale.getpreferredencoding()` returns ``'UTF-8'`` (the *do_setlocale*
+  argument has no effect).
+* :data:`sys.stdin`, :data:`sys.stdout`, and :data:`sys.stderr` all use
+  UTF-8 as their text encoding, with the ``surrogateescape``
+  :ref:`error handler <error-handlers>` being enabled for :data:`sys.stdin`
+  and :data:`sys.stdout` (:data:`sys.stderr` continues to use
+  ``backslashreplace`` as it does in the default locale-aware mode)
+* On Unix, :func:`os.device_encoding` returns ``'UTF-8'``. rather than the
+  device encoding.
+
+Note that the standard stream settings in UTF-8 mode can be overridden by
+:envvar:`PYTHONIOENCODING` (just as they can be in the default locale-aware
+mode).
+
+As a consequence of the changes in those lower level APIs, other higher
+level APIs also exhibit different default behaviours:
+
+* Command line arguments, environment variables and filenames are decoded
+  to text using the UTF-8 encoding.
+* :func:`os.fsdecode()` and :func:`os.fsencode()` use the UTF-8 encoding.
+* :func:`open()`, :func:`io.open()`, and :func:`codecs.open()` use the UTF-8
+  encoding by default. However, they still use the strict error handler by
+  default so that attempting to open a binary file in text mode is likely
+  to raise an exception rather than producing nonsense data.
+
+The :ref:`Python UTF-8 Mode <utf8-mode>` is enabled if the LC_CTYPE locale is
+``C`` or ``POSIX`` at Python startup (see the :c:func:`PyConfig_Read`
+function).
+
+It can be enabled or disabled using the :option:`-X utf8 <-X>` command line
+option and the :envvar:`PYTHONUTF8` environment variable.
+
+If the :envvar:`PYTHONUTF8` environment variable is not set at all, then the
+interpreter defaults to using the current locale settings, *unless* the current
+locale is identified as a legacy ASCII-based locale (as described for
+:envvar:`PYTHONCOERCECLOCALE`), and locale coercion is either disabled or
+fails. In such legacy locales, the interpreter will default to enabling UTF-8
+mode unless explicitly instructed not to do so.
+
+The Python UTF-8 Mode can only be enabled at the Python startup. Its value
+can be read from :data:`sys.flags.utf8_mode <sys.flags>`.
+
+See also the :ref:`UTF-8 mode on Windows <win-utf8-mode>`
+and the :term:`filesystem encoding and error handler`.
 
 
 .. _os-procinfo:
@@ -165,9 +233,9 @@ process and user.
 
 .. function:: fsencode(filename)
 
-   Encode :term:`path-like <path-like object>` *filename* to the filesystem
-   encoding with ``'surrogateescape'`` error handler, or ``'strict'`` on
-   Windows; return :class:`bytes` unchanged.
+   Encode :term:`path-like <path-like object>` *filename* to the
+   :term:`filesystem encoding and error handler`; return :class:`bytes`
+   unchanged.
 
    :func:`fsdecode` is the reverse function.
 
@@ -181,8 +249,8 @@ process and user.
 .. function:: fsdecode(filename)
 
    Decode the :term:`path-like <path-like object>` *filename* from the
-   filesystem encoding with ``'surrogateescape'`` error handler, or ``'strict'``
-   on Windows; return :class:`str` unchanged.
+   :term:`filesystem encoding and error handler`; return :class:`str`
+   unchanged.
 
    :func:`fsencode` is the reverse function.
 
@@ -742,6 +810,12 @@ as internal buffering of data.
    Return a string describing the encoding of the device associated with *fd*
    if it is connected to a terminal; else return :const:`None`.
 
+   On Unix, if the :ref:`Python UTF-8 Mode <utf8-mode>` is enabled, return
+   ``'UTF-8'`` rather than the device encoding.
+
+   .. versionchanged:: 3.10
+      On Unix, the function now implements the Python UTF-8 Mode.
+
 
 .. function:: dup(fd)
 
@@ -3246,7 +3320,7 @@ These functions are all available on Linux only.
    Removes the extended filesystem attribute *attribute* from *path*.
    *attribute* should be bytes or str (directly or indirectly through the
    :class:`PathLike` interface). If it is a string, it is encoded
-   with the filesystem encoding.
+   with the :term:`filesystem encoding and error handler`.
 
    This function can support :ref:`specifying a file descriptor <path_fd>` and
    :ref:`not following symlinks <follow_symlinks>`.
@@ -3262,7 +3336,7 @@ These functions are all available on Linux only.
    Set the extended filesystem attribute *attribute* on *path* to *value*.
    *attribute* must be a bytes or str with no embedded NULs (directly or
    indirectly through the :class:`PathLike` interface). If it is a str,
-   it is encoded with the filesystem encoding.  *flags* may be
+   it is encoded with the :term:`filesystem encoding and error handler`.  *flags* may be
    :data:`XATTR_REPLACE` or :data:`XATTR_CREATE`. If :data:`XATTR_REPLACE` is
    given and the attribute does not exist, ``EEXISTS`` will be raised.
    If :data:`XATTR_CREATE` is given and the attribute already exists, the

Doc/library/platform.rst

@@ -209,13 +209,6 @@ Windows Platform
    which means the OS version uses debugging code, i.e. code that checks arguments,
    ranges, etc.
 
-   .. note::
-
-      This function works best with Mark Hammond's
-      :mod:`win32all` package installed, but also on Python 2.3 and
-      later (support for this was added in Python 2.6). It obviously
-      only runs on Win32 compatible platforms.
-
 .. function:: win32_edition()
 
    Returns a string representing the current Windows edition.  Possible

Doc/library/posix.rst

@@ -37,7 +37,7 @@ Large File Support
 
 .. sectionauthor:: Steve Clift <clift@mail.anacapa.net>
 
-Several operating systems (including AIX, HP-UX, Irix and Solaris) provide
+Several operating systems (including AIX, HP-UX and Solaris) provide
 support for files that are larger than 2 GiB from a C programming model where
 :c:type:`int` and :c:type:`long` are 32-bit values. This is typically accomplished
 by defining the relevant size and offset types as 64-bit values. Such files are
@@ -47,8 +47,8 @@ Large file support is enabled in Python when the size of an :c:type:`off_t` is
 larger than a :c:type:`long` and the :c:type:`long long` is at least as large
 as an :c:type:`off_t`.
 It may be necessary to configure and compile Python with certain compiler flags
-to enable this mode. For example, it is enabled by default with recent versions
-of Irix, but with Solaris 2.6 and 2.7 you need to do something like::
+to enable this mode. For example, with Solaris 2.6 and 2.7 you need to do
+something like::
 
    CFLAGS="`getconf LFS_CFLAGS`" OPT="-g -O2 $CFLAGS" \
            ./configure

Doc/library/random.rst

@@ -319,6 +319,13 @@ be found in any statistics text.
    deviation.  This is slightly faster than the :func:`normalvariate` function
    defined below.
 
+   Multithreading note:  When two threads call this function
+   simultaneously, it is possible that they will receive the
+   same return value.  This can be avoided in three ways.
+   1) Have each thread use a different instance of the random
+   number generator. 2) Put locks around all calls. 3) Use the
+   slower, but thread-safe :func:`normalvariate` function instead.
+
 
 .. function:: lognormvariate(mu, sigma)
 

Doc/library/shelve.rst

@@ -25,8 +25,9 @@ lots of shared  sub-objects.  The keys are ordinary strings.
    database file is opened for reading and writing.  The optional *flag* parameter
    has the same interpretation as the *flag* parameter of :func:`dbm.open`.
 
-   By default, version 3 pickles are used to serialize values.  The version of the
-   pickle protocol can be specified with the *protocol* parameter.
+   By default, pickles created with :data:`pickle.DEFAULT_PROTOCOL` are used
+   to serialize values.  The version of the pickle protocol can be specified
+   with the *protocol* parameter.
 
    Because of Python semantics, a shelf cannot know when a mutable
    persistent-dictionary entry is modified.  By default modified objects are
@@ -40,6 +41,10 @@ lots of shared  sub-objects.  The keys are ordinary strings.
    determine which accessed entries are mutable, nor which ones were actually
    mutated).
 
+   .. versionchanged:: 3.10
+      :data:`pickle.DEFAULT_PROTOCOL` is now used as the default pickle
+      protocol.
+
    .. note::
 
       Do not rely on the shelf being closed automatically; always call
@@ -108,9 +113,10 @@ Restrictions
    A subclass of :class:`collections.abc.MutableMapping` which stores pickled
    values in the *dict* object.
 
-   By default, version 3 pickles are used to serialize values.  The version of the
-   pickle protocol can be specified with the *protocol* parameter. See the
-   :mod:`pickle` documentation for a discussion of the pickle protocols.
+   By default, pickles created with :data:`pickle.DEFAULT_PROTOCOL` are used
+   to serialize values.  The version of the pickle protocol can be specified
+   with the *protocol* parameter.  See the :mod:`pickle` documentation for a
+   discussion of the pickle protocols.
 
    If the *writeback* parameter is ``True``, the object will hold a cache of all
    entries accessed and write them back to the *dict* at sync and close times.
@@ -130,6 +136,10 @@ Restrictions
    .. versionchanged:: 3.4
       Added context manager support.
 
+   .. versionchanged:: 3.10
+      :data:`pickle.DEFAULT_PROTOCOL` is now used as the default pickle
+      protocol.
+
 
 .. class:: BsdDbShelf(dict, protocol=None, writeback=False, keyencoding='utf-8')
 

Doc/library/stdtypes.rst

@@ -4763,25 +4763,231 @@ define these methods must provide them as a normal Python accessible method.
 Compared to the overhead of setting up the runtime context, the overhead of a
 single class dictionary lookup is negligible.
 
+
+Type Annotation Types --- :ref:`Generic Alias <types-genericalias>`, :ref:`Union <types-union>`
+===============================================================================================
+
+.. index::
+   single: annotation; type annotation; type hint
+
+The core built-in types for :term:`type annotations <annotation>` are
+:ref:`Generic Alias <types-genericalias>` and :ref:`Union <types-union>`.
+
+
+.. _types-genericalias:
+
+Generic Alias Type
+------------------
+
+.. index::
+   object: GenericAlias
+   pair: Generic; Alias
+
+``GenericAlias`` objects are created by subscripting a class (usually a
+container), such as ``list[int]``.  They are intended primarily for
+:term:`type annotations <annotation>`.
+
+Usually, the :ref:`subscription <subscriptions>` of container objects calls the
+method :meth:`__getitem__` of the object.  However, the subscription of some
+containers' classes may call the classmethod :meth:`__class_getitem__` of the
+class instead. The classmethod :meth:`__class_getitem__` should return a
+``GenericAlias`` object.
+
+.. note::
+   If the :meth:`__getitem__` of the class' metaclass is present, it will take
+   precedence over the :meth:`__class_getitem__` defined in the class (see
+   :pep:`560` for more details).
+
+The ``GenericAlias`` object acts as a proxy for :term:`generic types
+<generic type>`, implementing *parameterized generics* - a specific instance
+of a generic which provides the types for container elements.
+
+The user-exposed type for the ``GenericAlias`` object can be accessed from
+:class:`types.GenericAlias` and used for :func:`isinstance` checks.  It can
+also be used to create ``GenericAlias`` objects directly.
+
+.. describe:: T[X, Y, ...]
+
+   Creates a ``GenericAlias`` representing a type ``T`` containing elements
+   of types *X*, *Y*, and more depending on the ``T`` used.
+   For example, a function expecting a :class:`list` containing
+   :class:`float` elements::
+
+      def average(values: list[float]) -> float:
+          return sum(values) / len(values)
+
+   Another example for :term:`mapping` objects, using a :class:`dict`, which
+   is a generic type expecting two type parameters representing the key type
+   and the value type.  In this example, the function expects a ``dict`` with
+   keys of type :class:`str` and values of type :class:`int`::
+
+      def send_post_request(url: str, body: dict[str, int]) -> None:
+          ...
+
+The builtin functions :func:`isinstance` and :func:`issubclass` do not accept
+``GenericAlias`` types for their second argument::
+
+   >>> isinstance([1, 2], list[str])
+   Traceback (most recent call last):
+     File "<stdin>", line 1, in <module>
+   TypeError: isinstance() argument 2 cannot be a parameterized generic
+
+The Python runtime does not enforce :term:`type annotations <annotation>`.
+This extends to generic types and their type parameters. When creating
+an object from a ``GenericAlias``, container elements are not checked
+against their type. For example, the following code is discouraged, but will
+run without errors::
+
+   >>> t = list[str]
+   >>> t([1, 2, 3])
+   [1, 2, 3]
+
+Furthermore, parameterized generics erase type parameters during object
+creation::
+
+   >>> t = list[str]
+   >>> type(t)
+   <class 'types.GenericAlias'>
+
+   >>> l = t()
+   >>> type(l)
+   <class 'list'>
+
+Calling :func:`repr` or :func:`str` on a generic shows the parameterized type::
+
+   >>> repr(list[int])
+   'list[int]'
+
+   >>> str(list[int])
+   'list[int]'
+
+The :meth:`__getitem__` method of generics will raise an exception to disallow
+mistakes like ``dict[str][str]``::
+
+   >>> dict[str][str]
+   Traceback (most recent call last):
+     File "<stdin>", line 1, in <module>
+   TypeError: There are no type variables left in dict[str]
+
+However, such expressions are valid when :ref:`type variables <generics>` are
+used.  The index must have as many elements as there are type variable items
+in the ``GenericAlias`` object's :attr:`__args__ <genericalias.__args__>`. ::
+
+   >>> from typing import TypeVar
+   >>> Y = TypeVar('Y')
+   >>> dict[str, Y][int]
+   dict[str, int]
+
+
+Standard Generic Collections
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+These standard library collections support parameterized generics.
+
+* :class:`tuple`
+* :class:`list`
+* :class:`dict`
+* :class:`set`
+* :class:`frozenset`
+* :class:`type`
+* :class:`collections.deque`
+* :class:`collections.defaultdict`
+* :class:`collections.OrderedDict`
+* :class:`collections.Counter`
+* :class:`collections.ChainMap`
+* :class:`collections.abc.Awaitable`
+* :class:`collections.abc.Coroutine`
+* :class:`collections.abc.AsyncIterable`
+* :class:`collections.abc.AsyncIterator`
+* :class:`collections.abc.AsyncGenerator`
+* :class:`collections.abc.Iterable`
+* :class:`collections.abc.Iterator`
+* :class:`collections.abc.Generator`
+* :class:`collections.abc.Reversible`
+* :class:`collections.abc.Container`
+* :class:`collections.abc.Collection`
+* :class:`collections.abc.Callable`
+* :class:`collections.abc.Set`
+* :class:`collections.abc.MutableSet`
+* :class:`collections.abc.Mapping`
+* :class:`collections.abc.MutableMapping`
+* :class:`collections.abc.Sequence`
+* :class:`collections.abc.MutableSequence`
+* :class:`collections.abc.ByteString`
+* :class:`collections.abc.MappingView`
+* :class:`collections.abc.KeysView`
+* :class:`collections.abc.ItemsView`
+* :class:`collections.abc.ValuesView`
+* :class:`contextlib.AbstractContextManager`
+* :class:`contextlib.AbstractAsyncContextManager`
+* :ref:`re.Pattern <re-objects>`
+* :ref:`re.Match <match-objects>`
+
+
+Special Attributes of Generic Alias
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+All parameterized generics implement special read-only attributes.
+
+.. attribute:: genericalias.__origin__
+
+   This attribute points at the non-parameterized generic class::
+
+      >>> list[int].__origin__
+      <class 'list'>
+
+
+.. attribute:: genericalias.__args__
+
+   This attribute is a :class:`tuple` (possibly of length 1) of generic
+   types passed to the original :meth:`__class_getitem__`
+   of the generic container::
+
+      >>> dict[str, list[int]].__args__
+      (<class 'str'>, list[int])
+
+
+.. attribute:: genericalias.__parameters__
+
+   This attribute is a lazily computed tuple (possibly empty) of unique type
+   variables found in ``__args__``::
+
+      >>> from typing import TypeVar
+
+      >>> T = TypeVar('T')
+      >>> list[T].__parameters__
+      (~T,)
+
+
+.. seealso::
+
+   * :pep:`585` -- "Type Hinting Generics In Standard Collections"
+   * :meth:`__class_getitem__` -- Used to implement parameterized generics.
+   * :ref:`generics` -- Generics in the :mod:`typing` module.
+
+.. versionadded:: 3.9
+
+
 .. _types-union:
 
 Union Type
-==========
+----------
 
 .. index::
    object: Union
    pair: union; type
 
 A union object holds the value of the ``|`` (bitwise or) operation on
-multiple :ref:`type objects<bltin-type-objects>`.  These types are intended
-primarily for type annotations. The union type expression enables cleaner
-type hinting syntax compared to :data:`typing.Union`.
+multiple :ref:`type objects <bltin-type-objects>`.  These types are intended
+primarily for :term:`type annotations <annotation>`. The union type expression
+enables cleaner type hinting syntax compared to :data:`typing.Union`.
 
 .. describe:: X | Y | ...
 
    Defines a union object which holds types *X*, *Y*, and so forth. ``X | Y``
    means either X or Y.  It is equivalent to ``typing.Union[X, Y]``.
-   Example::
+   For example, the following function expects an argument of type
+   :class:`int` or :class:`float`::
 
       def square(number: int | float) -> int | float:
           return number ** 2
@@ -4790,15 +4996,15 @@ type hinting syntax compared to :data:`typing.Union`.
 
    Union objects can be tested for equality with other union objects.  Details:
 
-   * Unions of unions are flattened, e.g.::
+   * Unions of unions are flattened::
 
        (int | str) | float == int | str | float
 
-   * Redundant types are removed, e.g.::
+   * Redundant types are removed::
 
        int | str | int == int | str
 
-   * When comparing unions, the order is ignored, e.g.::
+   * When comparing unions, the order is ignored::
 
       int | str == str | int
 
@@ -4817,14 +5023,8 @@ type hinting syntax compared to :data:`typing.Union`.
       >>> isinstance("", int | str)
       True
 
-   ..
-      At the time of writing this, there is no documentation for parameterized
-      generics or PEP 585. Thus the link currently points to PEP 585 itself.
-      Please change the link for parameterized generics to reference the correct
-      documentation once documentation for PEP 585 becomes available.
-
-   However, union objects containing `parameterized generics
-   <https://www.python.org/dev/peps/pep-0585/>`_ cannot be used::
+   However, union objects containing :ref:`parameterized generics
+   <types-genericalias>` cannot be used::
 
       >>> isinstance(1, int | list[int])
       Traceback (most recent call last):
@@ -4838,20 +5038,16 @@ type hinting syntax compared to :data:`typing.Union`.
       >>> issubclass(bool, int | str)
       True
 
-   ..
-      Once again, please change the link below for parameterized generics to
-      reference the correct documentation once documentation for PEP 585
-      becomes available.
-
-   However, union objects containing `parameterized generics
-   <https://www.python.org/dev/peps/pep-0585/>`_ cannot be used::
+   However, union objects containing :ref:`parameterized generics
+   <types-genericalias>` cannot be used::
 
       >>> issubclass(bool, bool | list[str])
       Traceback (most recent call last):
         File "<stdin>", line 1, in <module>
       TypeError: issubclass() argument 2 cannot contain a parameterized generic
 
-The type of a union object is :data:`types.Union`.  An object cannot be
+The user-exposed type for the union object can be accessed from
+:data:`types.Union` and used for :func:`isinstance` checks.  An object cannot be
 instantiated from the type::
 
    >>> import types

Doc/library/sys.rst

@@ -196,6 +196,18 @@ always available.
 
    .. audit-event:: sys._current_frames "" sys._current_frames
 
+.. function:: _current_exceptions()
+
+   Return a dictionary mapping each thread's identifier to the topmost exception
+   currently active in that thread at the time the function is called.
+   If a thread is not currently handling an exception, it is not included in
+   the result dictionary.
+
+   This is most useful for statistical profiling.
+
+   This function should be used for internal and specialized purposes only.
+
+   .. audit-event:: sys._current_exceptions "" sys._current_exceptions
 
 .. function:: breakpointhook()
 
@@ -615,30 +627,24 @@ always available.
 
 .. function:: getfilesystemencoding()
 
-   Return the name of the encoding used to convert between Unicode
-   filenames and bytes filenames. For best compatibility, str should be
-   used for filenames in all cases, although representing filenames as bytes
-   is also supported. Functions accepting or returning filenames should support
-   either str or bytes and internally convert to the system's preferred
-   representation.
+   Get the :term:`filesystem encoding <filesystem encoding and error handler>`:
+   the encoding used with the :term:`filesystem error handler <filesystem
+   encoding and error handler>` to convert between Unicode filenames and bytes
+   filenames. The filesystem error handler is returned from
+   :func:`getfilesystemencoding`.
 
-   This encoding is always ASCII-compatible.
+   For best compatibility, str should be used for filenames in all cases,
+   although representing filenames as bytes is also supported. Functions
+   accepting or returning filenames should support either str or bytes and
+   internally convert to the system's preferred representation.
 
    :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that
    the correct encoding and errors mode are used.
 
-   * In the UTF-8 mode, the encoding is ``utf-8`` on any platform.
-
-   * On macOS, the encoding is ``'utf-8'``.
-
-   * On Unix, the encoding is the locale encoding.
-
-   * On Windows, the encoding may be ``'utf-8'`` or ``'mbcs'``, depending
-     on user configuration.
-
-   * On Android, the encoding is ``'utf-8'``.
-
-   * On VxWorks, the encoding is ``'utf-8'``.
+   The :term:`filesystem encoding and error handler` are configured at Python
+   startup by the :c:func:`PyConfig_Read` function: see
+   :c:member:`~PyConfig.filesystem_encoding` and
+   :c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
 
    .. versionchanged:: 3.2
       :func:`getfilesystemencoding` result cannot be ``None`` anymore.
@@ -648,18 +654,26 @@ always available.
       and :func:`_enablelegacywindowsfsencoding` for more information.
 
    .. versionchanged:: 3.7
-      Return 'utf-8' in the UTF-8 mode.
+      Return ``'utf-8'`` if the :ref:`Python UTF-8 Mode <utf8-mode>` is
+      enabled.
 
 
 .. function:: getfilesystemencodeerrors()
 
-   Return the name of the error mode used to convert between Unicode filenames
-   and bytes filenames. The encoding name is returned from
+   Get the :term:`filesystem error handler <filesystem encoding and error
+   handler>`: the error handler used with the :term:`filesystem encoding
+   <filesystem encoding and error handler>` to convert between Unicode
+   filenames and bytes filenames. The filesystem encoding is returned from
    :func:`getfilesystemencoding`.
 
    :func:`os.fsencode` and :func:`os.fsdecode` should be used to ensure that
    the correct encoding and errors mode are used.
 
+   The :term:`filesystem encoding and error handler` are configured at Python
+   startup by the :c:func:`PyConfig_Read` function: see
+   :c:member:`~PyConfig.filesystem_encoding` and
+   :c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
+
    .. versionadded:: 3.6
 
 .. function:: getrefcount(object)
@@ -1451,12 +1465,16 @@ always available.
 
 .. function:: _enablelegacywindowsfsencoding()
 
-   Changes the default filesystem encoding and errors mode to 'mbcs' and
-   'replace' respectively, for consistency with versions of Python prior to 3.6.
+   Changes the :term:`filesystem encoding and error handler` to 'mbcs' and
+   'replace' respectively, for consistency with versions of Python prior to
+   3.6.
 
    This is equivalent to defining the :envvar:`PYTHONLEGACYWINDOWSFSENCODING`
    environment variable before launching Python.
 
+   See also :func:`sys.getfilesystemencoding` and
+   :func:`sys.getfilesystemencodeerrors`.
+
    .. availability:: Windows.
 
    .. versionadded:: 3.6
@@ -1479,9 +1497,8 @@ always available.
    returned by the :func:`open` function.  Their parameters are chosen as
    follows:
 
-   * The character encoding is platform-dependent.  Non-Windows
-     platforms use the locale encoding (see
-     :meth:`locale.getpreferredencoding()`).
+   * The encoding and error handling are is initialized from
+     :c:member:`PyConfig.stdio_encoding` and :c:member:`PyConfig.stdio_errors`.
 
      On Windows, UTF-8 is used for the console device.  Non-character
      devices such as disk files and pipes use the system locale
@@ -1489,7 +1506,7 @@ always available.
      devices such as NUL (i.e. where ``isatty()`` returns ``True``) use the
      value of the console input and output codepages at startup,
      respectively for stdin and stdout/stderr. This defaults to the
-     system locale encoding if the process is not initially attached
+     system :term:`locale encoding` if the process is not initially attached
      to a console.
 
      The special behaviour of the console can be overridden

Doc/library/threading.rst

@@ -121,6 +121,17 @@ This module defines the following functions:
    :meth:`~Thread.run` method is called.
 
 
+.. function:: gettrace()
+
+   .. index::
+      single: trace function
+      single: debugger
+
+   Get the trace function as set by :func:`settrace`.
+
+   .. versionadded:: 3.10
+
+
 .. function:: setprofile(func)
 
    .. index:: single: profile function
@@ -130,6 +141,15 @@ This module defines the following functions:
    :meth:`~Thread.run` method is called.
 
 
+.. function:: getprofile()
+
+   .. index:: single: profile function
+
+   Get the profiler function as set by :func:`setprofile`.
+
+   .. versionadded:: 3.10
+
+
 .. function:: stack_size([size])
 
    Return the thread stack size used when creating new threads.  The optional

Doc/library/traceback.rst

@@ -36,7 +36,8 @@ The module defines the following functions:
        Added negative *limit* support.
 
 
-.. function:: print_exception(etype, value, tb, limit=None, file=None, chain=True)
+.. function:: print_exception(exc, /[, value, tb], limit=None, \
+                              file=None, chain=True)
 
    Print exception information and stack trace entries from traceback object
    *tb* to *file*. This differs from :func:`print_tb` in the following
@@ -45,7 +46,7 @@ The module defines the following functions:
    * if *tb* is not ``None``, it prints a header ``Traceback (most recent
      call last):``
 
-   * it prints the exception *etype* and *value* after the stack trace
+   * it prints the exception type and *value* after the stack trace
 
    .. index:: single: ^ (caret); marker
 
@@ -53,6 +54,10 @@ The module defines the following functions:
      format, it prints the line where the syntax error occurred with a caret
      indicating the approximate position of the error.
 
+   Since Python 3.10, instead of passing *value* and *tb*, an exception object
+   can be passed as the first argument. If *value* and *tb* are provided, the
+   first argument is ignored in order to provide backwards compatibility.
+
    The optional *limit* argument has the same meaning as for :func:`print_tb`.
    If *chain* is true (the default), then chained exceptions (the
    :attr:`__cause__` or :attr:`__context__` attributes of the exception) will be
@@ -62,6 +67,10 @@ The module defines the following functions:
    .. versionchanged:: 3.5
       The *etype* argument is ignored and inferred from the type of *value*.
 
+   .. versionchanged:: 3.10
+      The *etype* parameter has been renamed to *exc* and is now
+      positional-only.
+
 
 .. function:: print_exc(limit=None, file=None, chain=True)
 
@@ -121,18 +130,26 @@ The module defines the following functions:
    text line is not ``None``.
 
 
-.. function:: format_exception_only(etype, value)
+.. function:: format_exception_only(exc, /[, value])
 
-   Format the exception part of a traceback.  The arguments are the exception
-   type and value such as given by ``sys.last_type`` and ``sys.last_value``.
-   The return value is a list of strings, each ending in a newline.  Normally,
-   the list contains a single string; however, for :exc:`SyntaxError`
-   exceptions, it contains several lines that (when printed) display detailed
-   information about where the syntax error occurred.  The message indicating
-   which exception occurred is the always last string in the list.
+   Format the exception part of a traceback using an exception value such as
+   given by ``sys.last_value``.  The return value is a list of strings, each
+   ending in a newline.  Normally, the list contains a single string; however,
+   for :exc:`SyntaxError` exceptions, it contains several lines that (when
+   printed) display detailed information about where the syntax error occurred.
+   The message indicating which exception occurred is the always last string in
+   the list.
+
+   Since Python 3.10, instead of passing *value*, an exception object
+   can be passed as the first argument.  If *value* is provided, the first
+   argument is ignored in order to provide backwards compatibility.
+
+   .. versionchanged:: 3.10
+      The *etype* parameter has been renamed to *exc* and is now
+      positional-only.
 
 
-.. function:: format_exception(etype, value, tb, limit=None, chain=True)
+.. function:: format_exception(exc, /[, value, tb], limit=None, chain=True)
 
    Format a stack trace and the exception information.  The arguments  have the
    same meaning as the corresponding arguments to :func:`print_exception`.  The
@@ -143,6 +160,10 @@ The module defines the following functions:
    .. versionchanged:: 3.5
       The *etype* argument is ignored and inferred from the type of *value*.
 
+   .. versionchanged:: 3.10
+      This function's behavior and signature were modified to match
+      :func:`print_exception`.
+
 
 .. function:: format_exc(limit=None, chain=True)
 

Doc/library/types.rst

@@ -262,6 +262,24 @@ Standard names are defined for the following types:
 
    .. versionadded:: 3.10
 
+.. class:: GenericAlias(t_origin, t_args)
+
+   The type of :ref:`parameterized generics <types-genericalias>` such as
+   ``list[int]``.
+
+   ``t_origin`` should be a non-parameterized generic class, such as ``list``,
+   ``tuple`` or ``dict``.  ``t_args`` should be a :class:`tuple` (possibly of
+   length 1) of types which parameterize ``t_origin``::
+
+      >>> from types import GenericAlias
+
+      >>> list[int] == GenericAlias(list, (int,))
+      True
+      >>> dict[str, int] == GenericAlias(dict, (str, int))
+      True
+
+   .. versionadded:: 3.9
+
 .. data:: Union
 
    The type of :ref:`union type expressions<types-union>`.

Doc/library/typing.rst

@@ -524,7 +524,8 @@ These can be used as types in annotations using ``[]``, each having a unique syn
    is equivalent to ``Tuple[Any, ...]``, and in turn to :class:`tuple`.
 
    .. deprecated:: 3.9
-      :class:`builtins.tuple <tuple>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.tuple <tuple>` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. data:: Union
 
@@ -602,7 +603,8 @@ These can be used as types in annotations using ``[]``, each having a unique syn
    :class:`collections.abc.Callable`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Callable` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Callable` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: Type(Generic[CT_co])
 
@@ -647,7 +649,8 @@ These can be used as types in annotations using ``[]``, each having a unique syn
    .. versionadded:: 3.5.2
 
    .. deprecated:: 3.9
-      :class:`builtins.type <type>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.type <type>` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. data:: Literal
 
@@ -1079,7 +1082,8 @@ Corresponding to built-in types
           ...
 
    .. deprecated:: 3.9
-      :class:`builtins.dict <dict>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.dict <dict>` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: List(list, MutableSequence[T])
 
@@ -1099,7 +1103,8 @@ Corresponding to built-in types
           return [item for item in vector if item > 0]
 
    .. deprecated:: 3.9
-      :class:`builtins.list <list>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.list <list>` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: Set(set, MutableSet[T])
 
@@ -1108,14 +1113,16 @@ Corresponding to built-in types
    to use an abstract collection type such as :class:`AbstractSet`.
 
    .. deprecated:: 3.9
-      :class:`builtins.set <set>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.set <set>` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: FrozenSet(frozenset, AbstractSet[T_co])
 
    A generic version of :class:`builtins.frozenset <frozenset>`.
 
    .. deprecated:: 3.9
-      :class:`builtins.frozenset <frozenset>` now supports ``[]``. See :pep:`585`.
+      :class:`builtins.frozenset <frozenset>` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 .. note:: :data:`Tuple` is a special form.
 
@@ -1129,7 +1136,8 @@ Corresponding to types in :mod:`collections`
    .. versionadded:: 3.5.2
 
    .. deprecated:: 3.9
-      :class:`collections.defaultdict` now supports ``[]``. See :pep:`585`.
+      :class:`collections.defaultdict` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: OrderedDict(collections.OrderedDict, MutableMapping[KT, VT])
 
@@ -1138,7 +1146,8 @@ Corresponding to types in :mod:`collections`
    .. versionadded:: 3.7.2
 
    .. deprecated:: 3.9
-      :class:`collections.OrderedDict` now supports ``[]``. See :pep:`585`.
+      :class:`collections.OrderedDict` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: ChainMap(collections.ChainMap, MutableMapping[KT, VT])
 
@@ -1148,7 +1157,8 @@ Corresponding to types in :mod:`collections`
    .. versionadded:: 3.6.1
 
    .. deprecated:: 3.9
-      :class:`collections.ChainMap` now supports ``[]``. See :pep:`585`.
+      :class:`collections.ChainMap` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: Counter(collections.Counter, Dict[T, int])
 
@@ -1158,7 +1168,8 @@ Corresponding to types in :mod:`collections`
    .. versionadded:: 3.6.1
 
    .. deprecated:: 3.9
-      :class:`collections.Counter` now supports ``[]``. See :pep:`585`.
+      :class:`collections.Counter` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: Deque(deque, MutableSequence[T])
 
@@ -1168,7 +1179,8 @@ Corresponding to types in :mod:`collections`
    .. versionadded:: 3.6.1
 
    .. deprecated:: 3.9
-      :class:`collections.deque` now supports ``[]``. See :pep:`585`.
+      :class:`collections.deque` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 Other concrete types
 """"""""""""""""""""
@@ -1193,7 +1205,8 @@ Other concrete types
    ``Match[bytes]``. These types are also in the ``typing.re`` namespace.
 
    .. deprecated:: 3.9
-      Classes ``Pattern`` and ``Match`` from :mod:`re` now support ``[]``. See :pep:`585`.
+      Classes ``Pattern`` and ``Match`` from :mod:`re` now support ``[]``.
+      See :pep:`585` and :ref:`types-genericalias`.
 
 .. class:: Text
 
@@ -1220,7 +1233,8 @@ Corresponding to collections in :mod:`collections.abc`
    A generic version of :class:`collections.abc.Set`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Set` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Set` now supports ``[]``. See :pep:`585` and
+      :ref:`types-genericalias`.
 
 .. class:: ByteString(Sequence[int])
 
@@ -1233,7 +1247,8 @@ Corresponding to collections in :mod:`collections.abc`
    annotate arguments of any of the types mentioned above.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.ByteString` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.ByteString` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Collection(Sized, Iterable[T_co], Container[T_co])
 
@@ -1242,28 +1257,32 @@ Corresponding to collections in :mod:`collections.abc`
    .. versionadded:: 3.6.0
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Collection` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Collection` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Container(Generic[T_co])
 
    A generic version of :class:`collections.abc.Container`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Container` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Container` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: ItemsView(MappingView, Generic[KT_co, VT_co])
 
    A generic version of :class:`collections.abc.ItemsView`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.ItemsView` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.ItemsView` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: KeysView(MappingView[KT_co], AbstractSet[KT_co])
 
    A generic version of :class:`collections.abc.KeysView`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.KeysView` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.KeysView` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Mapping(Sized, Collection[KT], Generic[VT_co])
 
@@ -1274,49 +1293,56 @@ Corresponding to collections in :mod:`collections.abc`
          return word_list[word]
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Mapping` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Mapping` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: MappingView(Sized, Iterable[T_co])
 
    A generic version of :class:`collections.abc.MappingView`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.MappingView` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.MappingView` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: MutableMapping(Mapping[KT, VT])
 
    A generic version of :class:`collections.abc.MutableMapping`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.MutableMapping` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.MutableMapping` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 .. class:: MutableSequence(Sequence[T])
 
    A generic version of :class:`collections.abc.MutableSequence`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.MutableSequence` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.MutableSequence` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 .. class:: MutableSet(AbstractSet[T])
 
    A generic version of :class:`collections.abc.MutableSet`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.MutableSet` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.MutableSet` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Sequence(Reversible[T_co], Collection[T_co])
 
    A generic version of :class:`collections.abc.Sequence`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Sequence` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Sequence` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: ValuesView(MappingView[VT_co])
 
    A generic version of :class:`collections.abc.ValuesView`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.ValuesView` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.ValuesView` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 Corresponding to other types in :mod:`collections.abc`
 """"""""""""""""""""""""""""""""""""""""""""""""""""""
@@ -1326,14 +1352,16 @@ Corresponding to other types in :mod:`collections.abc`
    A generic version of :class:`collections.abc.Iterable`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Iterable` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Iterable` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Iterator(Iterable[T_co])
 
    A generic version of :class:`collections.abc.Iterator`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Iterator` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Iterator` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Generator(Iterator[T_co], Generic[T_co, T_contra, V_co])
 
@@ -1367,7 +1395,8 @@ Corresponding to other types in :mod:`collections.abc`
               start += 1
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Generator` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Generator` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Hashable
 
@@ -1378,7 +1407,8 @@ Corresponding to other types in :mod:`collections.abc`
    A generic version of :class:`collections.abc.Reversible`.
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Reversible` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Reversible` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Sized
 
@@ -1403,7 +1433,8 @@ Asynchronous programming
    .. versionadded:: 3.5.3
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Coroutine` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Coroutine` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: AsyncGenerator(AsyncIterator[T_co], Generic[T_co, T_contra])
 
@@ -1439,7 +1470,8 @@ Asynchronous programming
    .. versionadded:: 3.6.1
 
    .. deprecated:: 3.9
-      :class:`collections.abc.AsyncGenerator` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.AsyncGenerator` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 .. class:: AsyncIterable(Generic[T_co])
 
@@ -1448,7 +1480,8 @@ Asynchronous programming
    .. versionadded:: 3.5.2
 
    .. deprecated:: 3.9
-      :class:`collections.abc.AsyncIterable` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.AsyncIterable` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: AsyncIterator(AsyncIterable[T_co])
 
@@ -1457,7 +1490,8 @@ Asynchronous programming
    .. versionadded:: 3.5.2
 
    .. deprecated:: 3.9
-      :class:`collections.abc.AsyncIterator` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.AsyncIterator` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 .. class:: Awaitable(Generic[T_co])
 
@@ -1466,7 +1500,8 @@ Asynchronous programming
    .. versionadded:: 3.5.2
 
    .. deprecated:: 3.9
-      :class:`collections.abc.Awaitable` now supports ``[]``. See :pep:`585`.
+      :class:`collections.abc.Awaitable` now supports ``[]``. See :pep:`585`
+      and :ref:`types-genericalias`.
 
 
 Context manager types
@@ -1480,7 +1515,8 @@ Context manager types
    .. versionadded:: 3.6.0
 
    .. deprecated:: 3.9
-      :class:`contextlib.AbstractContextManager` now supports ``[]``. See :pep:`585`.
+      :class:`contextlib.AbstractContextManager` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 .. class:: AsyncContextManager(Generic[T_co])
 
@@ -1490,7 +1526,8 @@ Context manager types
    .. versionadded:: 3.6.2
 
    .. deprecated:: 3.9
-      :class:`contextlib.AbstractAsyncContextManager` now supports ``[]``. See :pep:`585`.
+      :class:`contextlib.AbstractAsyncContextManager` now supports ``[]``. See
+      :pep:`585` and :ref:`types-genericalias`.
 
 Protocols
 ---------

Doc/library/xml.etree.elementtree.rst

@@ -455,6 +455,12 @@ Supported XPath syntax
 |                       | has the given value.  The value cannot contain       |
 |                       | quotes.                                              |
 +-----------------------+------------------------------------------------------+
+| ``[@attrib!='value']``| Selects all elements for which the given attribute   |
+|                       | does not have the given value. The value cannot      |
+|                       | contain quotes.                                      |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[tag]``             | Selects all elements that have a child named         |
 |                       | ``tag``.  Only immediate children are supported.     |
 +-----------------------+------------------------------------------------------+
@@ -463,10 +469,22 @@ Supported XPath syntax
 |                       |                                                      |
 |                       | .. versionadded:: 3.7                                |
 +-----------------------+------------------------------------------------------+
+| ``[.!='text']``       | Selects all elements whose complete text content,    |
+|                       | including descendants, does not equal the given      |
+|                       | ``text``.                                            |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[tag='text']``      | Selects all elements that have a child named         |
 |                       | ``tag`` whose complete text content, including       |
 |                       | descendants, equals the given ``text``.              |
 +-----------------------+------------------------------------------------------+
+| ``[tag!='text']``     | Selects all elements that have a child named         |
+|                       | ``tag`` whose complete text content, including       |
+|                       | descendants, does not equal the given ``text``.      |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[position]``        | Selects all elements that are located at the given   |
 |                       | position.  The position can be either an integer     |
 |                       | (1 is the first position), the expression ``last()`` |

Doc/reference/datamodel.rst

@@ -2168,7 +2168,7 @@ Emulating callable objects
    .. index:: pair: call; instance
 
    Called when the instance is "called" as a function; if this method is defined,
-   ``x(arg1, arg2, ...)`` is a shorthand for ``x.__call__(arg1, arg2, ...)``.
+   ``x(arg1, arg2, ...)`` roughly translates to ``type(x).__call__(x, arg1, ...)``.
 
 
 .. _sequence-types:

Doc/reference/expressions.rst

@@ -643,6 +643,16 @@ after resuming depends on the method which resumed the execution.  If
 :meth:`~agen.asend` is used, then the result will be the value passed in to
 that method.
 
+If an asynchronous generator happens to exit early by :keyword:`break`, the caller
+task being cancelled, or other exceptions, the generator's async cleanup code
+will run and possibly raise exceptions or access context variables in an
+unexpected context--perhaps after the lifetime of tasks it depends, or
+during the event loop shutdown when the async-generator garbage collection hook
+is called.
+To prevent this, the caller must explicitly close the async generator by calling
+:meth:`~agen.aclose` method to finalize the generator and ultimately detach it
+from the event loop.
+
 In an asynchronous generator function, yield expressions are allowed anywhere
 in a :keyword:`try` construct. However, if an asynchronous generator is not
 resumed before it is finalized (by reaching a zero reference count or by
@@ -654,9 +664,9 @@ generator-iterator's :meth:`~agen.aclose` method and run the resulting
 coroutine object, thus allowing any pending :keyword:`!finally` clauses
 to execute.
 
-To take care of finalization, an event loop should define
-a *finalizer* function which takes an asynchronous generator-iterator
-and presumably calls :meth:`~agen.aclose` and executes the coroutine.
+To take care of finalization upon event loop termination, an event loop should
+define a *finalizer* function which takes an asynchronous generator-iterator and
+presumably calls :meth:`~agen.aclose` and executes the coroutine.
 This  *finalizer* may be registered by calling :func:`sys.set_asyncgen_hooks`.
 When first iterated over, an asynchronous generator-iterator will store the
 registered *finalizer* to be called upon finalization. For a reference example
@@ -837,14 +847,8 @@ this method will need to explicitly add that support.
 A string's items are characters.  A character is not a separate data type but a
 string of exactly one character.
 
-..
-   At the time of writing this, there is no documentation for generic alias
-   or PEP 585.  Thus the link currently points to PEP 585 itself.
-   Please change the link for generic alias to reference the correct
-   documentation once documentation for PEP 585 becomes available.
-
 Subscription of certain :term:`classes <class>` or :term:`types <type>`
-creates a `generic alias <https://www.python.org/dev/peps/pep-0585/>`_.
+creates a :ref:`generic alias <types-genericalias>`.
 In this case, user-defined classes can support subscription by providing a
 :meth:`__class_getitem__` classmethod.
 

Doc/tools/static/switchers.js

@@ -1,156 +0,0 @@
-(function() {
-  'use strict';
-
-  // Parses versions in URL segments like:
-  // "3", "dev", "release/2.7" or "3.6rc2"
-  var version_regexs = [
-    '(?:\\d)',
-    '(?:\\d\\.\\d[\\w\\d\\.]*)',
-    '(?:dev)',
-    '(?:release/\\d.\\d[\\x\\d\\.]*)'];
-
-  var all_versions = {
-    '3.10': 'dev (3.10)',
-    '3.9': 'pre (3.9)',
-    '3.8': '3.8',
-    '3.7': '3.7',
-    '3.6': '3.6',
-    '2.7': '2.7',
-  };
-
-  var all_languages = {
-      'en': 'English',
-      'fr': 'French',
-      'ja': 'Japanese',
-      'ko': 'Korean',
-      'pt-br': 'Brazilian Portuguese',
-      'zh-cn': 'Simplified Chinese',
-  };
-
-  function build_version_select(current_version, current_release) {
-    var buf = ['<select>'];
-
-    $.each(all_versions, function(version, title) {
-      buf.push('<option value="' + version + '"');
-      if (version == current_version)
-        buf.push(' selected="selected">' + current_release + '</option>');
-      else
-        buf.push('>' + title + '</option>');
-    });
-
-    buf.push('</select>');
-    return buf.join('');
-  }
-
-  function build_language_select(current_language) {
-    var buf = ['<select>'];
-
-    $.each(all_languages, function(language, title) {
-      if (language == current_language)
-        buf.push('<option value="' + language + '" selected="selected">' +
-                 all_languages[current_language] + '</option>');
-      else
-        buf.push('<option value="' + language + '">' + title + '</option>');
-    });
-    if (!(current_language in all_languages)) {
-        // In case we're browsing a language that is not yet in all_languages.
-        buf.push('<option value="' + current_language + '" selected="selected">' +
-                 current_language + '</option>');
-        all_languages[current_language] = current_language;
-    }
-    buf.push('</select>');
-    return buf.join('');
-  }
-
-  function navigate_to_first_existing(urls) {
-    // Navigate to the first existing URL in urls.
-    var url = urls.shift();
-    if (urls.length == 0) {
-      window.location.href = url;
-      return;
-    }
-    $.ajax({
-      url: url,
-      success: function() {
-        window.location.href = url;
-      },
-      error: function() {
-        navigate_to_first_existing(urls);
-      }
-    });
-  }
-
-  function on_version_switch() {
-    var selected_version = $(this).children('option:selected').attr('value') + '/';
-    var url = window.location.href;
-    var current_language = language_segment_from_url(url);
-    var current_version = version_segment_in_url(url);
-    var new_url = url.replace('.org/' + current_language + current_version,
-                              '.org/' + current_language + selected_version);
-    if (new_url != url) {
-      navigate_to_first_existing([
-        new_url,
-        url.replace('.org/' + current_language + current_version,
-                    '.org/' + selected_version),
-        'https://docs.python.org/' + current_language + selected_version,
-        'https://docs.python.org/' + selected_version,
-        'https://docs.python.org/'
-      ]);
-    }
-  }
-
-  function on_language_switch() {
-    var selected_language = $(this).children('option:selected').attr('value') + '/';
-    var url = window.location.href;
-    var current_language = language_segment_from_url(url);
-    var current_version = version_segment_in_url(url);
-    if (selected_language == 'en/') // Special 'default' case for english.
-      selected_language = '';
-    var new_url = url.replace('.org/' + current_language + current_version,
-                              '.org/' + selected_language + current_version);
-    if (new_url != url) {
-      navigate_to_first_existing([
-        new_url,
-        'https://docs.python.org/'
-      ]);
-    }
-  }
-
-  // Returns the path segment of the language as a string, like 'fr/'
-  // or '' if not found.
-  function language_segment_from_url(url) {
-    var language_regexp = '\.org/([a-z]{2}(?:-[a-z]{2})?/)';
-    var match = url.match(language_regexp);
-    if (match !== null)
-        return match[1];
-    return '';
-  }
-
-  // Returns the path segment of the version as a string, like '3.6/'
-  // or '' if not found.
-  function version_segment_in_url(url) {
-    var language_segment = '(?:[a-z]{2}(?:-[a-z]{2})?/)';
-    var version_segment = '(?:(?:' + version_regexs.join('|') + ')/)';
-    var version_regexp = '\\.org/' + language_segment + '?(' + version_segment + ')';
-    var match = url.match(version_regexp);
-    if (match !== null)
-      return match[1];
-    return ''
-  }
-
-  $(document).ready(function() {
-    var release = DOCUMENTATION_OPTIONS.VERSION;
-    var language_segment = language_segment_from_url(window.location.href);
-    var current_language = language_segment.replace(/\/+$/g, '') || 'en';
-    var version = release.substr(0, 3);
-    var version_select = build_version_select(version, release);
-
-    $('.version_switcher_placeholder').html(version_select);
-    $('.version_switcher_placeholder select').bind('change', on_version_switch);
-
-    var language_select = build_language_select(current_language);
-
-    $('.language_switcher_placeholder').html(language_select);
-    $('.language_switcher_placeholder select').bind('change', on_language_switch);
-  });
-})();

Doc/tools/susp-ignored.csv

@@ -5,7 +5,7 @@ c-api/sequence,,:i2,o[i1:i2]
 c-api/tuple,,:high,p[low:high]
 c-api/unicode,,:end,str[start:end]
 c-api/unicode,,:start,unicode[start:start+length]
-distutils/examples,267,`,This is the description of the ``foobar`` package.
+distutils/examples,,`,This is the description of the ``foobar`` package.
 distutils/setupscript,,::,
 extending/embedding,,:numargs,"if(!PyArg_ParseTuple(args, "":numargs""))"
 extending/extending,,:myfunction,"PyArg_ParseTuple(args, ""D:myfunction"", &c);"
@@ -23,6 +23,9 @@ howto/curses,,:blue,"2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.
 howto/curses,,:magenta,"2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.  The"
 howto/curses,,:cyan,"2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.  The"
 howto/curses,,:white,"2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.  The"
+howto/descriptor,,:root,"INFO:root"
+howto/descriptor,,:Updating,"root:Updating"
+howto/descriptor,,:Accessing,"root:Accessing"
 howto/instrumentation,,::,python$target:::function-entry
 howto/instrumentation,,:function,python$target:::function-entry
 howto/instrumentation,,::,python$target:::function-return
@@ -144,8 +147,10 @@ library/ipaddress,,:db8,IPv6Address('2001:db8::')
 library/ipaddress,,::,IPv6Address('2001:db8::')
 library/ipaddress,,:db8,>>> ipaddress.IPv6Address('2001:db8::1000')
 library/ipaddress,,::,>>> ipaddress.IPv6Address('2001:db8::1000')
-library/ipaddress,,:db8,IPv6Address('2001:db8::1000')
-library/ipaddress,,::,IPv6Address('2001:db8::1000')
+library/ipaddress,,:db8,'2001:db8::1000'
+library/ipaddress,,::,'2001:db8::1000'
+library/ipaddress,231,:db8,">>> f'{ipaddress.IPv6Address(""2001:db8::1000""):s}'"
+library/ipaddress,231,::,">>> f'{ipaddress.IPv6Address(""2001:db8::1000""):s}'"
 library/ipaddress,,::,IPv6Address('ff02::5678%1')
 library/ipaddress,,::,fe80::1234
 library/ipaddress,,:db8,">>> ipaddress.ip_address(""2001:db8::1"").reverse_pointer"

Doc/tools/templates/dummy.html

@@ -6,3 +6,12 @@ In extensions/pyspecific.py:
 {% trans %}CPython implementation detail:{% endtrans %}
 {% trans %}Deprecated since version {deprecated}, will be removed in version {removed}{% endtrans %}
 {% trans %}Deprecated since version {deprecated}, removed in version {removed}{% endtrans %}
+
+
+In docsbuild-scripts, when rewriting indexsidebar.html with actual versions:
+
+{% trans %}in development{% endtrans %}
+{% trans %}pre-release{% endtrans %}
+{% trans %}stable{% endtrans %}
+{% trans %}security-fixes{% endtrans %}
+{% trans %}EOL{% endtrans %}

Doc/tools/templates/indexsidebar.html

@@ -2,12 +2,8 @@
 <p><a href="{{ pathto('download') }}">{% trans %}Download these documents{% endtrans %}</a></p>
 <h3>{% trans %}Docs by version{% endtrans %}</h3>
 <ul>
-  <li><a href="https://docs.python.org/3.10/">{% trans %}Python 3.10 (in development){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.9/">{% trans %}Python 3.9 (pre-release){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.8/">{% trans %}Python 3.8 (stable){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.7/">{% trans %}Python 3.7 (stable){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.6/">{% trans %}Python 3.6 (security-fixes){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/2.7/">{% trans %}Python 2.7 (EOL){% endtrans %}</a></li>
+  <li><a href="https://docs.python.org/">{% trans %}Stable{% endtrans %}</a></li>
+  <li><a href="https://docs.python.org/dev/">{% trans %}In development{% endtrans %}</a></li>
   <li><a href="https://www.python.org/doc/versions/">{% trans %}All versions{% endtrans %}</a></li>
 </ul>
 

Doc/tools/templates/layout.html

@@ -12,22 +12,14 @@
 
 {% block rootrellink %}
 {{ super() }}
-    <li>
-      {%- if switchers is defined %}
-      <span class="language_switcher_placeholder">{{ language or 'en' }}</span>
-      <span class="version_switcher_placeholder">{{ release }}</span>
-      <a href="{{ pathto('index') }}">{% trans %}Documentation {% endtrans %}</a>{{ reldelim1 }}
-      {%- else %}
+    <li id="cpython-language-and-version">
       <a href="{{ pathto('index') }}">{{ shorttitle }}</a>{{ reldelim1 }}
-      {%- endif %}
     </li>
 {% endblock %}
 
 {% block extrahead %}
     <link rel="canonical" href="https://docs.python.org/3/{{pagename}}.html" />
     {% if builder != "htmlhelp" %}
-      {% if switchers is defined and not embedded %}
-      <script type="text/javascript" src="{{ pathto('_static/switchers.js', 1) }}"></script>{% endif %}
       {% if pagename == 'whatsnew/changelog' and not embedded %}
       <script type="text/javascript" src="{{ pathto('_static/changelog_search.js', 1) }}"></script>{% endif %}
     {% endif %}

Doc/tutorial/errors.rst

@@ -273,15 +273,15 @@ Exception Chaining
 ==================
 
 The :keyword:`raise` statement allows an optional :keyword:`from` which enables
-chaining exceptions by setting the ``__cause__`` attribute of the raised
-exception. For example::
+chaining exceptions. For example::
 
-    raise RuntimeError from OSError
+    # exc must be exception instance or None.
+    raise RuntimeError from exc
 
 This can be useful when you are transforming exceptions. For example::
 
     >>> def func():
-    ...    raise IOError
+    ...     raise IOError
     ...
     >>> try:
     ...     func()
@@ -297,12 +297,11 @@ This can be useful when you are transforming exceptions. For example::
     <BLANKLINE>
     Traceback (most recent call last):
       File "<stdin>", line 4, in <module>
-    RuntimeError
+    RuntimeError: Failed to open database
 
-The expression following the :keyword:`from` must be either an exception or
-``None``. Exception chaining happens automatically when an exception is raised
-inside an exception handler or :keyword:`finally` section. Exception chaining
-can be disabled by using ``from None`` idiom:
+Exception chaining happens automatically when an exception is raised inside an
+:keyword:`except` or :keyword:`finally` section. Exception chaining can be
+disabled by using ``from None`` idiom:
 
     >>> try:
     ...     open('database.sqlite')
@@ -313,6 +312,8 @@ can be disabled by using ``from None`` idiom:
       File "<stdin>", line 4, in <module>
     RuntimeError
 
+For more information about chaining mechanics, see :ref:`bltin-exceptions`.
+
 
 .. _tut-userexceptions:
 

Doc/using/cmdline.rst

@@ -447,10 +447,9 @@ Miscellaneous options
    * ``-X dev``: enable :ref:`Python Development Mode <devmode>`, introducing
      additional runtime checks that are too expensive to be enabled by
      default.
-   * ``-X utf8`` enables UTF-8 mode for operating system interfaces, overriding
-     the default locale-aware mode. ``-X utf8=0`` explicitly disables UTF-8
-     mode (even when it would otherwise activate automatically).
-     See :envvar:`PYTHONUTF8` for more details.
+   * ``-X utf8`` enables the :ref:`Python UTF-8 Mode <utf8-mode>`.
+     ``-X utf8=0`` explicitly disables :ref:`Python UTF-8 Mode <utf8-mode>`
+     (even when it would otherwise activate automatically).
    * ``-X pycache_prefix=PATH`` enables writing ``.pyc`` files to a parallel
      tree rooted at the given directory instead of to the code tree. See also
      :envvar:`PYTHONPYCACHEPREFIX`.
@@ -810,9 +809,10 @@ conflict.
 
 .. envvar:: PYTHONLEGACYWINDOWSFSENCODING
 
-   If set to a non-empty string, the default filesystem encoding and errors mode
-   will revert to their pre-3.6 values of 'mbcs' and 'replace', respectively.
-   Otherwise, the new defaults 'utf-8' and 'surrogatepass' are used.
+   If set to a non-empty string, the default :term:`filesystem encoding and
+   error handler` mode will revert to their pre-3.6 values of 'mbcs' and
+   'replace', respectively.  Otherwise, the new defaults 'utf-8' and
+   'surrogatepass' are used.
 
    This may also be enabled at runtime with
    :func:`sys._enablelegacywindowsfsencoding()`.
@@ -898,54 +898,14 @@ conflict.
 
 .. envvar:: PYTHONUTF8
 
-   If set to ``1``, enables the interpreter's UTF-8 mode, where ``UTF-8`` is
-   used as the text encoding for system interfaces, regardless of the
-   current locale setting.
+   If set to ``1``, enable the :ref:`Python UTF-8 Mode <utf8-mode>`.
 
-   This means that:
-
-    * :func:`sys.getfilesystemencoding()` returns ``'UTF-8'`` (the locale
-      encoding is ignored).
-    * :func:`locale.getpreferredencoding()` returns ``'UTF-8'`` (the locale
-      encoding is ignored, and the function's ``do_setlocale`` parameter has no
-      effect).
-    * :data:`sys.stdin`, :data:`sys.stdout`, and :data:`sys.stderr` all use
-      UTF-8 as their text encoding, with the ``surrogateescape``
-      :ref:`error handler <error-handlers>` being enabled for :data:`sys.stdin`
-      and :data:`sys.stdout` (:data:`sys.stderr` continues to use
-      ``backslashreplace`` as it does in the default locale-aware mode)
-
-   As a consequence of the changes in those lower level APIs, other higher
-   level APIs also exhibit different default behaviours:
-
-    * Command line arguments, environment variables and filenames are decoded
-      to text using the UTF-8 encoding.
-    * :func:`os.fsdecode()` and :func:`os.fsencode()` use the UTF-8 encoding.
-    * :func:`open()`, :func:`io.open()`, and :func:`codecs.open()` use the UTF-8
-      encoding by default. However, they still use the strict error handler by
-      default so that attempting to open a binary file in text mode is likely
-      to raise an exception rather than producing nonsense data.
-
-   Note that the standard stream settings in UTF-8 mode can be overridden by
-   :envvar:`PYTHONIOENCODING` (just as they can be in the default locale-aware
-   mode).
-
-   If set to ``0``, the interpreter runs in its default locale-aware mode.
+   If set to ``0``, disable the :ref:`Python UTF-8 Mode <utf8-mode>`.
 
    Setting any other non-empty string causes an error during interpreter
    initialisation.
 
-   If this environment variable is not set at all, then the interpreter defaults
-   to using the current locale settings, *unless* the current locale is
-   identified as a legacy ASCII-based locale
-   (as described for :envvar:`PYTHONCOERCECLOCALE`), and locale coercion is
-   either disabled or fails. In such legacy locales, the interpreter will
-   default to enabling UTF-8 mode unless explicitly instructed not to do so.
-
-   Also available as the :option:`-X` ``utf8`` option.
-
    .. versionadded:: 3.7
-      See :pep:`540` for more details.
 
 
 Debug-mode variables

Doc/using/windows.rst

@@ -614,21 +614,14 @@ Page).  Python uses it for the default encoding of text files (e.g.
 This may cause issues because UTF-8 is widely used on the internet
 and most Unix systems, including WSL (Windows Subsystem for Linux).
 
-You can use UTF-8 mode to change the default text encoding to UTF-8.
-You can enable UTF-8 mode via the ``-X utf8`` command line option, or
-the ``PYTHONUTF8=1`` environment variable.  See :envvar:`PYTHONUTF8` for
-enabling UTF-8 mode, and :ref:`setting-envvars` for how to modify
-environment variables.
+You can use the :ref:`Python UTF-8 Mode <utf8-mode>` to change the default text
+encoding to UTF-8. You can enable the :ref:`Python UTF-8 Mode <utf8-mode>` via
+the ``-X utf8`` command line option, or the ``PYTHONUTF8=1`` environment
+variable.  See :envvar:`PYTHONUTF8` for enabling UTF-8 mode, and
+:ref:`setting-envvars` for how to modify environment variables.
 
-When UTF-8 mode is enabled:
-
-* :func:`locale.getpreferredencoding` returns ``'UTF-8'`` instead of
-  the system encoding.  This function is used for the default text
-  encoding in many places, including :func:`open`, :class:`Popen`,
-  :meth:`Path.read_text`, etc.
-* :data:`sys.stdin`, :data:`sys.stdout`, and :data:`sys.stderr`
-  all use UTF-8 as their text encoding.
-* You can still use the system encoding via the "mbcs" codec.
+When the :ref:`Python UTF-8 Mode <utf8-mode>` is enabled, you can still use the
+system encoding (the ANSI Code Page) via the "mbcs" codec.
 
 Note that adding ``PYTHONUTF8=1`` to the default environment variables
 will affect all Python 3.7+ applications on your system.
@@ -641,7 +634,8 @@ temporarily or use the ``-X utf8`` command line option.
    on Windows for:
 
    * Console I/O including standard I/O (see :pep:`528` for details).
-   * The filesystem encoding (see :pep:`529` for details).
+   * The :term:`filesystem encoding <filesystem encoding and error handler>`
+     (see :pep:`529` for details).
 
 
 .. _launcher:

Doc/whatsnew/3.10.rst

@@ -134,7 +134,7 @@ arguments of multiple types, :data:`typing.Union` was used::
        return number ** 2
 
 
-Now, type hints can be written in a more succinct manner::
+Type hints can now be written in a more succinct manner::
 
    def square(number: int | float) -> int | float:
        return number ** 2
@@ -176,6 +176,13 @@ codecs
 Add a :func:`codecs.unregister` function to unregister a codec search function.
 (Contributed by Hai Shi in :issue:`41842`.)
 
+contextlib
+----------
+
+Add a :func:`contextlib.aclosing` context manager to safely close async generators
+and objects representing asynchronously released resources.
+(Contributed by Joongi Kim and John Belmonte in :issue:`41229`.)
+
 curses
 ------
 
@@ -186,6 +193,12 @@ by :func:`curses.color_content`, :func:`curses.init_color`,
 support is provided by the underlying ncurses library.
 (Contributed by Jeffrey Kintscher and Hans Petter Jansson in :issue:`36982`.)
 
+doctest
+-------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 encodings
 ---------
 :func:`encodings.normalize_encoding` now ignores non-ASCII characters.
@@ -198,6 +211,18 @@ Added the *root_dir* and *dir_fd* parameters in :func:`~glob.glob` and
 :func:`~glob.iglob` which allow to specify the root directory for searching.
 (Contributed by Serhiy Storchaka in :issue:`38144`.)
 
+inspect
+-------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
+linecache
+---------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 os
 --
 
@@ -210,6 +235,19 @@ py_compile
 Added ``--quiet`` option to command-line interface of :mod:`py_compile`.
 (Contributed by Gregory Schevchenko in :issue:`38731`.)
 
+shelve
+------
+
+The :mod:`shelve` module now uses :data:`pickle.DEFAULT_PROTOCOL` by default
+instead of :mod:`pickle` protocol ``3`` when creating shelves.
+(Contributed by Zackery Spytz in :issue:`34204`.)
+
+site
+----
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 sys
 ---
 
@@ -217,6 +255,23 @@ Add :data:`sys.orig_argv` attribute: the list of the original command line
 arguments passed to the Python executable.
 (Contributed by Victor Stinner in :issue:`23427`.)
 
+threading
+---------
+
+Added :func:`threading.gettrace` and :func:`threading.getprofile` to
+retrieve the functions set by :func:`threading.settrace` and
+:func:`threading.setprofile` respectively.
+(Contributed by Mario Corchero in :issue:`42251`.)
+
+traceback
+---------
+
+The :func:`~traceback.format_exception`,
+:func:`~traceback.format_exception_only`, and
+:func:`~traceback.print_exception` functions can now take an exception object
+as a positional-only argument.
+(Contributed by Zackery Spytz and Matthias Bussonnier in :issue:`26389`.)
+
 types
 -----
 
@@ -254,7 +309,7 @@ Optimizations
 
 * The ``LOAD_ATTR`` instruction now uses new "per opcode cache" mechanism.
   It is about 36% faster now.  (Contributed by Pablo Galindo and Yury Selivanov
-  in :issue:`42093`.)
+  in :issue:`42093`, based on ideas implemented originally in PyPy and MicroPython.)
 
 * When building Python with ``--enable-optimizations`` now
   ``-fno-semantic-interposition`` is added to both the compile and link line.
@@ -267,6 +322,23 @@ Optimizations
 Deprecated
 ==========
 
+* Starting in this release, there will be a concerted effort to begin
+  cleaning up old import semantics that were kept for Python 2.7
+  compatibility. Specifically,
+  :meth:`~importlib.abc.PathEntryFinder.find_loader`/:meth:`~importlib.abc.Finder.find_module`
+  (superseded by :meth:`~importlib.abc.Finder.find_spec`),
+  :meth:`~importlib.abc.Loader.load_module`
+  (superseded by :meth:`~importlib.abc.Loader.exec_module`),
+  :meth:`~importlib.abc.Loader.module_repr` (which the import system
+  takes care of for you), the ``__package__`` attribute
+  (superseded by ``__spec__.parent``), the ``__loader__`` attribute
+  (superseded by ``__spec__.loader``), and the ``__cached__`` attribute
+  (superseded by ``__spec__.cached``) will slowly be removed (as well
+  as other classes and methods in :mod:`importlib`).
+  :exc:`ImportWarning` and/or :exc:`DeprecationWarning` will be raised
+  as appropriate to help identify code which needs updating during
+  this transition.
+
 
 Removed
 =======
@@ -283,6 +355,11 @@ Removed
   Python 3.5.
   (Contributed by Berker Peksag in :issue:`31844`.)
 
+* Removed the ``unicodedata.ucnhash_CAPI`` attribute which was an internal
+  PyCapsule object. The related private ``_PyUnicode_Name_CAPI`` structure was
+  moved to the internal C API.
+  (Contributed by Victor Stinner in :issue:`42157`.)
+
 
 Porting to Python 3.10
 ======================
@@ -291,6 +368,15 @@ This section lists previously described changes and other bugfixes
 that may require changes to your code.
 
 
+Changes in the Python API
+-------------------------
+
+* The *etype* parameters of the :func:`~traceback.format_exception`,
+  :func:`~traceback.format_exception_only`, and
+  :func:`~traceback.print_exception` functions in the :mod:`traceback` module
+  have been renamed to *exc*.
+  (Contributed by Zackery Spytz and Matthias Bussonnier in :issue:`26389`.)
+
 
 Build Changes
 =============
@@ -337,6 +423,19 @@ New Features
 * Added :c:func:`PyUnicode_AsUTF8AndSize` to the limited C API.
   (Contributed by Alex Gaynor in :issue:`41784`.)
 
+* Added :c:func:`PyModule_AddObjectRef` function: similar to
+  :c:func:`PyModule_AddObjectRef` but don't steal a reference to the value on
+  success.
+  (Contributed by Victor Stinner in :issue:`1635741`.)
+
+* Added :c:func:`Py_NewRef` and :c:func:`Py_XNewRef` functions to increment the
+  reference count of an object and return the object.
+  (Contributed by Victor Stinner in :issue:`42262`.)
+
+* The :c:func:`PyType_FromModuleAndSpec` function now accepts NULL ``tp_doc``
+  slot.
+  (Contributed by Hai Shi in :issue:`41832`.)
+
 
 Porting to Python 3.10
 ----------------------
@@ -390,6 +489,10 @@ Porting to Python 3.10
   Unicode object without initial data.
   (Contributed by Inada Naoki in :issue:`36346`.)
 
+* The private ``_PyUnicode_Name_CAPI`` structure of the PyCapsule API
+  ``unicodedata.ucnhash_CAPI`` has been moved to the internal C API.
+  (Contributed by Victor Stinner in :issue:`42157`.)
+
 Deprecated
 ----------
 

Doc/whatsnew/3.7.rst

@@ -232,7 +232,8 @@ PEP 540: Forced UTF-8 Runtime Mode
 -----------------------------------
 
 The new :option:`-X` ``utf8`` command line option and :envvar:`PYTHONUTF8`
-environment variable can be used to enable the CPython *UTF-8 mode*.
+environment variable can be used to enable the :ref:`Python UTF-8 Mode
+<utf8-mode>`.
 
 When in UTF-8 mode, CPython ignores the locale settings, and uses the
 UTF-8 encoding by default.  The error handlers for :data:`sys.stdin` and

Doc/whatsnew/3.9.rst

@@ -4,22 +4,21 @@
 
 :Release: |release|
 :Date: |today|
+:Editor: Łukasz Langa
 
 .. Rules for maintenance:
 
-   * Anyone can add text to this document.  Do not spend very much time
-   on the wording of your changes, because your text will probably
-   get rewritten to some degree.
+   * Anyone can add text to this document.  Your text might get
+   rewritten to some degree.
 
    * The maintainer will go through Misc/NEWS periodically and add
    changes; it's therefore more important to add your changes to
    Misc/NEWS than to this file.
 
    * This is not a complete list of every single change; completeness
-   is the purpose of Misc/NEWS.  Some changes I consider too small
+   is the purpose of Misc/NEWS.  Some changes will be too small
    or esoteric to include.  If such a change is added to the text,
-   I'll just remove it.  (This is another reason you shouldn't spend
-   too much time on writing your addition.)
+   it might get removed during final editing.
 
    * If you want to draw your new text to the attention of the
    maintainer, add 'XXX' to the beginning of the paragraph or
@@ -46,14 +45,13 @@
    when researching a change.
 
 This article explains the new features in Python 3.9, compared to 3.8.
+Python 3.9 was released on October 5th, 2020.
 
 For full details, see the :ref:`changelog <changelog>`.
 
-.. note::
+.. seealso::
 
-   Prerelease users should be aware that this document is currently in draft
-   form. It will be updated substantially as Python 3.9 moves towards release,
-   so it's worth checking back even after reading earlier versions.
+    :pep:`596` - Python 3.9 Release Schedule
 
 
 Summary -- Release highlights
@@ -62,27 +60,70 @@ Summary -- Release highlights
 .. This section singles out the most important changes in Python 3.9.
    Brevity is key.
 
+New syntax features:
 
-.. PEP-sized items next.
+* :pep:`584`, union operators added to ``dict``;
+* :pep:`585`, type hinting generics in standard collections;
+* :pep:`614`, relaxed grammar restrictions on decorators.
+
+New built-in features:
+
+* :pep:`616`, string methods to remove prefixes and suffixes.
+
+New features in the standard library:
+
+* :pep:`593`, flexible function and variable annotations;
+* :func:`os.pidfd_open` added that allows process management without races
+  and signals.
+
+Interpreter improvements:
+
+* :pep:`573`, fast access to module state from methods of C extension
+  types;
+* :pep:`617`, CPython now uses a new parser based on PEG;
+* a number of Python builtins (range, tuple, set, frozenset, list, dict) are
+  now sped up using :pep:`590` vectorcall;
+* garbage collection does not block on resurrected objects;
+* a number of Python modules (:mod:`_abc`, :mod:`audioop`, :mod:`_bz2`,
+  :mod:`_codecs`, :mod:`_contextvars`, :mod:`_crypt`, :mod:`_functools`,
+  :mod:`_json`, :mod:`_locale`, :mod:`math`, :mod:`operator`, :mod:`resource`,
+  :mod:`time`, :mod:`_weakref`) now use multiphase initialization as defined
+  by PEP 489;
+* a number of standard library modules (:mod:`audioop`, :mod:`ast`, :mod:`grp`,
+  :mod:`_hashlib`, :mod:`pwd`, :mod:`_posixsubprocess`, :mod:`random`,
+  :mod:`select`, :mod:`struct`, :mod:`termios`, :mod:`zlib`) are now using
+  the stable ABI defined by PEP 384.
+
+New library modules:
+
+* :pep:`615`, the IANA Time Zone Database is now present in the standard
+  library in the :mod:`zoneinfo` module;
+* an implementation of a topological sort of a graph is now provided in
+  the new :mod:`graphlib` module.
+
+Release process changes:
+
+* :pep:`602`, CPython adopts an annual release cycle.
 
 
 You should check for DeprecationWarning in your code
 ====================================================
 
-When Python 2.7 was still supported, many functions were kept for backward
-compatibility with Python 2.7. With the end of Python 2.7 support, these
-backward compatibility layers have been removed, or will be removed soon.
-Most of them emitted a :exc:`DeprecationWarning` warning for several years. For
-example, using ``collections.Mapping`` instead of ``collections.abc.Mapping``
-emits a :exc:`DeprecationWarning` since Python 3.3, released in 2012.
+When Python 2.7 was still supported, a lot of functionality in Python 3
+was kept for backward compatibility with Python 2.7. With the end of Python
+2 support, these backward compatibility layers have been removed, or will
+be removed soon. Most of them emitted a :exc:`DeprecationWarning` warning for
+several years. For example, using ``collections.Mapping`` instead of
+``collections.abc.Mapping`` emits a :exc:`DeprecationWarning` since Python
+3.3, released in 2012.
 
 Test your application with the :option:`-W` ``default`` command-line option to see
 :exc:`DeprecationWarning` and :exc:`PendingDeprecationWarning`, or even with
 :option:`-W` ``error`` to treat them as errors. :ref:`Warnings Filter
 <warning-filter>` can be used to ignore warnings from third-party code.
 
-It has been decided to keep a few backward compatibility layers for one last
-release, to give more time to Python projects maintainers to organize the
+Python 3.9 is the last version providing those Python 2 backward compatibility
+layers, to give more time to Python projects maintainers to organize the
 removal of the Python 2 support and add support for Python 3.9.
 
 Aliases to :ref:`Abstract Base Classes <collections-abstract-base-classes>` in
@@ -94,6 +135,9 @@ More generally, try to run your tests in the :ref:`Python Development Mode
 <devmode>` which helps to prepare your code to make it compatible with the
 next Python version.
 
+Note: a number of pre-existing deprecatations were removed in this version
+of Python as well. Consult the :ref:`removed-in-python-39` section.
+
 
 New Features
 ============
@@ -102,11 +146,23 @@ Dictionary Merge & Update Operators
 -----------------------------------
 
 Merge (``|``) and update (``|=``) operators have been added to the built-in
-:class:`dict` class.  See :pep:`584` for a full description.
+:class:`dict` class. Those complement the existing ``dict.update`` and
+``{**d1, **d2}`` methods of merging dictionaries.
+
+Example::
+
+  >>> x = {"key1": "value1 from x", "key2": "value2 from x"}
+  >>> y = {"key2": "value2 from y", "key3": "value3 from y"}
+  >>> x | y
+  {'key1': 'value1 from x', 'key2': 'value2 from y', 'key3': 'value3 from y'}
+  >>> y | x
+  {'key2': 'value2 from x', 'key3': 'value3 from y', 'key1': 'value1 from x'}
+
+See :pep:`584` for a full description.
 (Contributed by Brandt Bucher in :issue:`36144`.)
 
-PEP 616: New removeprefix() and removesuffix() string methods
--------------------------------------------------------------
+New String Methods to Remove Prefixes and Suffixes
+--------------------------------------------------
 
 :meth:`str.removeprefix(prefix)<str.removeprefix>` and
 :meth:`str.removesuffix(suffix)<str.removesuffix>` have been added
@@ -115,8 +171,8 @@ to easily remove an unneeded prefix or a suffix from a string. Corresponding
 added. See :pep:`616` for a full description. (Contributed by Dennis Sweeney in
 :issue:`39939`.)
 
-PEP 585: Builtin Generic Types
-------------------------------
+Type Hinting Generics in Standard Collections
+---------------------------------------------
 
 In type annotations you can now use built-in collection types such as
 ``list`` and ``dict`` as generic types instead of importing the
@@ -135,8 +191,8 @@ Example:
 See :pep:`585` for more details.  (Contributed by Guido van Rossum,
 Ethan Smith, and Batuhan Taşkaya in :issue:`39481`.)
 
-PEP 617: New Parser
--------------------
+New Parser
+----------
 
 Python 3.9 uses a new parser, based on `PEG
 <https://en.wikipedia.org/wiki/Parsing_expression_grammar>`_ instead
@@ -167,7 +223,6 @@ Other Language Changes
   its top-level package.
   (Contributed by Ngalim Siregar in :issue:`37444`.)
 
-
 * Python now gets the absolute path of the script filename specified on
   the command line (ex: ``python3 script.py``): the ``__file__`` attribute of
   the :mod:`__main__` module became an absolute path, rather than a relative
@@ -201,6 +256,17 @@ Other Language Changes
   for the correspondent concrete type (``list`` in this case).
   (Contributed by Serhiy Storchaka in :issue:`40257`.)
 
+* Parallel running of :meth:`~agen.aclose` / :meth:`~agen.asend` /
+  :meth:`~agen.athrow` is now prohibited, and ``ag_running`` now reflects
+  the actual running status of the async generator.
+  (Contributed by Yury Selivanov in :issue:`30773`.)
+
+* Unexpected errors in calling the ``__iter__`` method are no longer masked by
+  ``TypeError`` in the :keyword:`in` operator and functions
+  :func:`~operator.contains`, :func:`~operator.indexOf` and
+  :func:`~operator.countOf` of the :mod:`operator` module.
+  (Contributed by Serhiy Storchaka in :issue:`40824`.)
+
 
 New Modules
 ===========
@@ -248,9 +314,10 @@ PyPI and maintained by the CPython core team.
 graphlib
 ---------
 
-Add the :mod:`graphlib` that contains the :class:`graphlib.TopologicalSorter` class
-to offer functionality to perform topological sorting of graphs. (Contributed by Pablo
-Galindo, Tim Peters and Larry Hastings in :issue:`17005`.)
+A new module, :mod:`graphlib`, was added that contains the
+:class:`graphlib.TopologicalSorter` class to offer functionality to perform
+topological sorting of graphs. (Contributed by Pablo Galindo, Tim Peters and
+Larry Hastings in :issue:`17005`.)
 
 
 Improved Modules
@@ -296,6 +363,15 @@ loop, and essentially works as a high-level version of
 :meth:`~asyncio.loop.run_in_executor` that can directly take keyword arguments.
 (Contributed by Kyle Stanley and Yury Selivanov in :issue:`32309`.)
 
+When cancelling the task due to a timeout, :meth:`asyncio.wait_for` will now
+wait until the cancellation is complete also in the case when *timeout* is
+<= 0, like it does with positive timeouts.
+(Contributed by Elvis Pranskevichus in :issue:`32751`.)
+
+:mod:`asyncio` now raises :exc:`TyperError` when calling incompatible
+methods with an :class:`ssl.SSLSocket` socket.
+(Contributed by Ido Michael in :issue:`37404`.)
+
 compileall
 ----------
 
@@ -328,7 +404,7 @@ startup overhead and reduces the amount of lost CPU time to idle workers.
 curses
 ------
 
-Add :func:`curses.get_escdelay`, :func:`curses.set_escdelay`,
+Added :func:`curses.get_escdelay`, :func:`curses.set_escdelay`,
 :func:`curses.get_tabsize`, and :func:`curses.set_tabsize` functions.
 (Contributed by Anthony Sottile in :issue:`38312`.)
 
@@ -375,12 +451,17 @@ finalized by the garbage collector. (Contributed by Pablo Galindo in
 hashlib
 -------
 
+The :mod:`hashlib` module can now use SHA3 hashes and SHAKE XOF from OpenSSL
+when available.
+(Contributed by Christian Heimes in :issue:`37630`.)
+
 Builtin hash modules can now be disabled with
 ``./configure --without-builtin-hashlib-hashes`` or selectively enabled with
 e.g. ``./configure --with-builtin-hashlib-hashes=sha3,blake2`` to force use
 of OpenSSL based implementation.
 (Contributed by Christian Heimes in :issue:`40479`)
 
+
 http
 ----
 
@@ -390,13 +471,13 @@ HTTP status codes ``103 EARLY_HINTS``, ``418 IM_A_TEAPOT`` and ``425 TOO_EARLY``
 IDLE and idlelib
 ----------------
 
-Add option to toggle cursor blink off.  (Contributed by Zackery Spytz
+Added option to toggle cursor blink off.  (Contributed by Zackery Spytz
 in :issue:`4603`.)
 
 Escape key now closes IDLE completion windows.  (Contributed by Johnny
 Najera in :issue:`38944`.)
 
-Add keywords to module name completion list.  (Contributed by Terry J.
+Added keywords to module name completion list.  (Contributed by Terry J.
 Reedy in :issue:`37765`.)
 
 The changes above have been backported to 3.8 maintenance releases.
@@ -426,6 +507,17 @@ now raises :exc:`ImportError` instead of :exc:`ValueError` for invalid relative
 import attempts.
 (Contributed by Ngalim Siregar in :issue:`37444`.)
 
+Import loaders which publish immutable module objects can now publish
+immutable packages in addition to individual modules.
+(Contributed by Dino Viehland in :issue:`39336`.)
+
+Added :func:`importlib.resources.files` function with support for
+subdirectories in package data, matching backport in ``importlib_resources``
+version 1.5.
+(Contributed by Jason R. Coombs in :issue:`39791`.)
+
+Refreshed ``importlib.metadata`` from ``importlib_metadata`` version 1.6.1.
+
 inspect
 -------
 
@@ -448,15 +540,15 @@ Expanded the :func:`math.gcd` function to handle multiple arguments.
 Formerly, it only supported two arguments.
 (Contributed by Serhiy Storchaka in :issue:`39648`.)
 
-Add :func:`math.lcm`: return the least common multiple of specified arguments.
+Added :func:`math.lcm`: return the least common multiple of specified arguments.
 (Contributed by Mark Dickinson, Ananthakrishnan and Serhiy Storchaka in
 :issue:`39479` and :issue:`39648`.)
 
-Add :func:`math.nextafter`: return the next floating-point value after *x*
+Added :func:`math.nextafter`: return the next floating-point value after *x*
 towards *y*.
 (Contributed by Victor Stinner in :issue:`39288`.)
 
-Add :func:`math.ulp`: return the value of the least significant bit
+Added :func:`math.ulp`: return the value of the least significant bit
 of a float.
 (Contributed by Victor Stinner in :issue:`39310`.)
 
@@ -492,7 +584,7 @@ The :func:`os.putenv` and :func:`os.unsetenv` functions are now always
 available.
 (Contributed by Victor Stinner in :issue:`39395`.)
 
-Add :func:`os.waitstatus_to_exitcode` function:
+Added :func:`os.waitstatus_to_exitcode` function:
 convert a wait status to an exit code.
 (Contributed by Victor Stinner in :issue:`40094`.)
 
@@ -503,6 +595,12 @@ Added :meth:`pathlib.Path.readlink()` which acts similarly to
 :func:`os.readlink`.
 (Contributed by Girts Folkmanis in :issue:`30618`)
 
+pdb
+---
+
+On Windows now :class:`~pdb.Pdb` supports ``~/.pdbrc``.
+(Contributed by Tim Hopper and Dan Lidral-Porter in :issue:`20523`.)
+
 poplib
 ------
 
@@ -526,7 +624,7 @@ method etc, but for any object that has its own ``__doc__`` attribute.
 random
 ------
 
-Add a new :attr:`random.Random.randbytes` method: generate random bytes.
+Added a new :attr:`random.Random.randbytes` method: generate random bytes.
 (Contributed by Victor Stinner in :issue:`40286`.)
 
 signal
@@ -555,6 +653,11 @@ constant on Linux 4.1 and greater.
 The socket module now supports the :data:`~socket.CAN_J1939` protocol on
 platforms that support it.  (Contributed by Karl Ding in :issue:`40291`.)
 
+The socket module now has the :func:`socket.send_fds` and
+:func:`socket.recv.fds` methods. (Contributed by Joannah Nanjekye, Shinya
+Okano and Victor Stinner in :issue:`28724`.)
+
+
 time
 ----
 
@@ -566,7 +669,7 @@ which has nanosecond resolution, rather than
 sys
 ---
 
-Add a new :attr:`sys.platlibdir` attribute: name of the platform-specific
+Added a new :attr:`sys.platlibdir` attribute: name of the platform-specific
 library directory. It is used to build the path of standard library and the
 paths of installed extension modules. It is equal to ``"lib"`` on most
 platforms.  On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit platforms.
@@ -630,7 +733,7 @@ Optimizations
 
   (Contributed by Serhiy Storchaka in :issue:`32856`.)
 
-* Optimize signal handling in multithreaded applications. If a thread different
+* Optimized signal handling in multithreaded applications. If a thread different
   than the main thread gets a signal, the bytecode evaluation loop is no longer
   interrupted at each bytecode instruction to check for pending signals which
   cannot be handled. Only the main thread of the main interpreter can handle
@@ -640,10 +743,36 @@ Optimizations
   until the main thread handles signals.
   (Contributed by Victor Stinner in :issue:`40010`.)
 
-* Optimize the :mod:`subprocess` module on FreeBSD using ``closefrom()``.
+* Optimized the :mod:`subprocess` module on FreeBSD using ``closefrom()``.
   (Contributed by Ed Maste, Conrad Meyer, Kyle Evans, Kubilay Kocak and Victor
   Stinner in :issue:`38061`.)
 
+* :c:func:`PyLong_FromDouble` is now up to 1.87x faster for values that
+  fit into :c:type:`long`.
+  (Contributed by Sergey Fedoseev in :issue:`37986`.)
+
+* A number of Python builtins (:class:`range`, :class:`tuple`, :class:`set`,
+  :class:`frozenset`, :class:`list`, :class:`dict`) are now sped up by using
+  :pep:`590` vectorcall protocol.
+  (Contributed by Dong-hee Na, Mark Shannon, Jeroen Demeyer and Petr Viktorin in :issue:`37207`.)
+
+* Optimized :func:`~set.difference_update` for the case when the other set
+  is much larger than the base set.
+  (Suggested by Evgeny Kapun with code contributed by Michele Orrù in :issue:`8425`.)
+
+* Python's small object allocator (``obmalloc.c``) now allows (no more than)
+  one empty arena to remain available for immediate reuse, without returning
+  it to the OS.  This prevents thrashing in simple loops where an arena could
+  be created and destroyed anew on each iteration.
+  (Contributed by Tim Peters in :issue:`37257`.)
+
+* :term:`floor division` of float operation now has a better performance. Also
+  the message of :exc:`ZeroDivisionError` for this operation is updated.
+  (Contributed by Dong-hee Na in :issue:`39434`.)
+
+* Decoding short ASCII strings with UTF-8 and ascii codecs is now about
+  15% faster.  (Contributed by Inada Naoki in :issue:`37348`.)
+
 Here's a summary of performance improvements from Python 3.4 through Python 3.9:
 
 .. code-block:: none
@@ -699,10 +828,6 @@ in nanoseconds.  The benchmarks were measured on an
 running the macOS 64-bit builds found at
 `python.org <https://www.python.org/downloads/mac-osx/>`_.
 
-* A number of Python builtins (:class:`range`, :class:`tuple`, :class:`set`, :class:`frozenset`, :class:`list`, :class:`dict`)
-  are now sped up by using :pep:`590` vectorcall protocol.
-  (Contributed by Dong-hee Na, Mark Shannon, Jeroen Demeyer and Petr Viktorin in :issue:`37207`.)
-
 
 Deprecated
 ==========
@@ -784,6 +909,9 @@ Deprecated
 * Passing ``None`` as the first argument to the :func:`shlex.split` function
   has been deprecated.  (Contributed by Zackery Spytz in :issue:`33262`.)
 
+* :func:`smtpd.MailmanProxy` is now deprecated as it is unusable without
+  an external module, ``mailman``.  (Contributed by Samuel Colvin in :issue:`35800`.)
+
 * The :mod:`lib2to3` module now emits a :exc:`PendingDeprecationWarning`.
   Python 3.9 switched to a PEG parser (see :pep:`617`), and Python 3.10 may
   include new language syntax that is not parsable by lib2to3's LL(1) parser.
@@ -798,6 +926,8 @@ Deprecated
 .. _LibCST: https://libcst.readthedocs.io/
 .. _parso: https://parso.readthedocs.io/
 
+.. _removed-in-python-39:
+
 Removed
 =======
 
@@ -967,6 +1097,19 @@ Changes in the Python API
   of ``wchar_t`` since Python 3.3.
   (Contributed by Inada Naoki in :issue:`34538`.)
 
+* The :func:`logging.getLogger` API now returns the root logger when passed
+  the name ``'root'``, whereas previously it returned a non-root logger named
+  ``'root'``. This could affect cases where user code explicitly wants a
+  non-root logger named ``'root'``, or instantiates a logger using
+  ``logging.getLogger(__name__)`` in some top-level module called ``'root.py'``.
+  (Contributed by Vinay Sajip in :issue:`37742`.)
+
+* Division handling of :class:`~pathlib.PurePath` now returns ``NotImplemented``
+  instead of raising a :exc:`TypeError` when passed something other than an
+  instance of ``str`` or :class:`~pathlib.PurePath`.  This allows creating
+  compatible classes that don't inherit from those mentioned types.
+  (Contributed by Roger Aiudi in :issue:`34775`).
+
 
 Changes in the C API
 --------------------
@@ -1017,6 +1160,11 @@ Changes in the C API
 
   (See :issue:`35810` and :issue:`40217` for more information.)
 
+* The functions ``PyEval_CallObject``, ``PyEval_CallFunction``,
+  ``PyEval_CallMethod`` and ``PyEval_CallObjectWithKeywords`` are deprecated.
+  Use :c:func:`PyObject_Call` and its variants instead.
+  (See more details in :issue:`29548`.)
+
 CPython bytecode changes
 ------------------------
 
@@ -1025,11 +1173,21 @@ CPython bytecode changes
   correctly if the :exc:`AssertionError` exception was being shadowed.
   (Contributed by Zackery Spytz in :issue:`34880`.)
 
+* The :opcode:`COMPARE_OP` opcode was split into four distinct instructions:
+
+  * ``COMPARE_OP`` for rich comparisons
+  * ``IS_OP`` for 'is' and 'is not' tests
+  * ``CONTAINS_OP`` for 'in' and 'not in' tests
+  * ``JUMP_IF_NOT_EXC_MATCH`` for checking exceptions in 'try-except'
+    statements.
+
+  (Contributed by Mark Shannon in :issue:`39156`.)
+
 
 Build Changes
 =============
 
-* Add ``--with-platlibdir`` option to the ``configure`` script: name of the
+* Added ``--with-platlibdir`` option to the ``configure`` script: name of the
   platform-specific library directory, stored in the new :attr:`sys.platlibdir`
   attribute. See :attr:`sys.platlibdir` attribute for more information.
   (Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis
@@ -1042,6 +1200,34 @@ Build Changes
   functions are now required to build Python.
   (Contributed by Victor Stinner in :issue:`39395`.)
 
+* On non-Windows platforms, creating ``bdist_wininst`` installers is now
+  officially unsupported.  (See :issue:`10945` for more details.)
+
+* When building Python on macOS from source, ``_tkinter`` now links with
+  non-system Tcl and Tk frameworks if they are installed in
+  ``/Library/Frameworks``, as had been the case on older releases
+  of macOS. If a macOS SDK is explicitly configured, by using
+  ``--enable-universalsdk=`` or ``-isysroot``, only the SDK itself is
+  searched. The default behavior can still be overridden with
+  ``--with-tcltk-includes`` and ``--with-tcltk-libs``.
+  (Contributed by Ned Deily in :issue:`34956`.)
+
+* Python can now be built for Windows 10 ARM64.
+  (Contributed by Steve Dower in :issue:`33125`.)
+
+* Some individual tests are now skipped when ``--pgo`` is used.  The tests
+  in question increased the PGO task time significantly and likely
+  didn't help improve optimization of the final executable. This
+  speeds up the task by a factor of about 15x.  Running the full unit test
+  suite is slow.  This change may result in a slightly less optimized build
+  since not as many code branches will be executed.  If you are willing to
+  wait for the much slower build, the old behavior can be restored using
+  ``./configure [..] PROFILE_TASK="-m test --pgo-extended"``.  We make no
+  guarantees as to which PGO task set produces a faster build.  Users who care
+  should run their own relevant benchmarks as results can depend on the
+  environment, workload, and compiler tool chain.
+  (See :issue:`36044` and :issue:`37707` for more details.)
+
 
 C API Changes
 =============
@@ -1049,29 +1235,29 @@ C API Changes
 New Features
 ------------
 
-* :pep:`573`: Add :c:func:`PyType_FromModuleAndSpec` to associate
+* :pep:`573`: Added :c:func:`PyType_FromModuleAndSpec` to associate
   a module with a class; :c:func:`PyType_GetModule` and
   :c:func:`PyType_GetModuleState` to retrieve the module and its state; and
   :c:data:`PyCMethod` and :c:data:`METH_METHOD` to allow a method to
   access the class it was defined in.
   (Contributed by Marcel Plch and Petr Viktorin in :issue:`38787`.)
 
-* Add :c:func:`PyFrame_GetCode` function: get a frame code.
-  Add :c:func:`PyFrame_GetBack` function: get the frame next outer frame.
+* Added :c:func:`PyFrame_GetCode` function: get a frame code.
+  Added :c:func:`PyFrame_GetBack` function: get the frame next outer frame.
   (Contributed by Victor Stinner in :issue:`40421`.)
 
-* Add :c:func:`PyFrame_GetLineNumber` to the limited C API.
+* Added :c:func:`PyFrame_GetLineNumber` to the limited C API.
   (Contributed by Victor Stinner in :issue:`40421`.)
 
-* Add :c:func:`PyThreadState_GetInterpreter` and
+* Added :c:func:`PyThreadState_GetInterpreter` and
   :c:func:`PyInterpreterState_Get` functions to get the interpreter.
-  Add :c:func:`PyThreadState_GetFrame` function to get the current frame of a
+  Added :c:func:`PyThreadState_GetFrame` function to get the current frame of a
   Python thread state.
-  Add :c:func:`PyThreadState_GetID` function: get the unique identifier of a
+  Added :c:func:`PyThreadState_GetID` function: get the unique identifier of a
   Python thread state.
   (Contributed by Victor Stinner in :issue:`39947`.)
 
-* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API, which
+* Added a new public :c:func:`PyObject_CallNoArgs` function to the C API, which
   calls a callable Python object without any arguments. It is the most efficient
   way to call a callable Python object without any argument.
   (Contributed by Victor Stinner in :issue:`37194`.)
@@ -1093,11 +1279,19 @@ New Features
   to a module.
   (Contributed by Dong-hee Na in :issue:`40024`.)
 
-* Add the functions :c:func:`PyObject_GC_IsTracked` and
+* Added the functions :c:func:`PyObject_GC_IsTracked` and
   :c:func:`PyObject_GC_IsFinalized` to the public API to allow to query if
   Python objects are being currently tracked or have been already finalized by
-  the garbage collector respectively. (Contributed by Pablo Galindo in
-  :issue:`40241`.)
+  the garbage collector respectively.
+  (Contributed by Pablo Galindo Salgado in :issue:`40241`.)
+
+* Added :c:func:`_PyObject_FunctionStr` to get a user-friendly string
+  representation of a function-like object.
+  (Patch by Jeroen Demeyer in :issue:`37645`.)
+
+* Added :c:func:`PyObject_CallOneArg` for calling an object with one
+  positional argument
+  (Patch by Jeroen Demeyer in :issue:`37483`.)
 
 
 Porting to Python 3.9
@@ -1144,10 +1338,44 @@ Porting to Python 3.9
   Python 3.3.
   (Contributed by Inada Naoki in :issue:`36346`.)
 
+* The :c:func:`Py_FatalError` function is replaced with a macro which logs
+  automatically the name of the current function, unless the
+  ``Py_LIMITED_API`` macro is defined.
+  (Contributed by Victor Stinner in :issue:`39882`.)
+
+* The vectorcall protocol now requires that the caller passes only strings as
+  keyword names. (See :issue:`37540` for more information.)
+
+* Implementation details of a number of macros and functions are now hidden:
+
+  * :c:func:`PyObject_IS_GC` macro was converted to a function.
+
+  * The :c:func:`PyObject_NEW` macro becomes an alias to the
+    :c:func:`PyObject_New` macro, and the :c:func:`PyObject_NEW_VAR` macro
+    becomes an alias to the :c:func:`PyObject_NewVar` macro. They no longer
+    access directly the :c:member:`PyTypeObject.tp_basicsize` member.
+
+  * :c:func:`PyType_HasFeature` now always calls :c:func:`PyType_GetFlags`.
+    Previously, it accessed directly the :c:member:`PyTypeObject.tp_flags`
+    member when the limited C API was not used.
+
+  * :c:func:`PyObject_GET_WEAKREFS_LISTPTR` macro was converted to a function:
+    the macro accessed directly the :c:member:`PyTypeObject.tp_weaklistoffset`
+    member.
+
+  * :c:func:`PyObject_CheckBuffer` macro was converted to a function: the macro
+    accessed directly the :c:member:`PyTypeObject.tp_as_buffer` member.
+
+  * :c:func:`PyIndex_Check` is now always declared as an opaque function to hide
+    implementation details: removed the ``PyIndex_Check()`` macro. The macro accessed
+    directly the :c:member:`PyTypeObject.tp_as_number` member.
+
+  (See :issue:`40170` for more details.)
+
 Removed
 -------
 
-* Exclude ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()`` macros of
+* Excluded ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()`` macros of
   ``pyfpe.h`` from the limited C API.
   (Contributed by Victor Stinner in :issue:`38835`.)
 
@@ -1158,7 +1386,7 @@ Removed
 
 * Changes in the limited C API (if ``Py_LIMITED_API`` macro is defined):
 
-  * Exclude the following functions from the limited C API:
+  * Excluded the following functions from the limited C API:
 
     * ``PyThreadState_DeleteCurrent()``
       (Contributed by Joannah Nanjekye in :issue:`37878`.)
@@ -1175,7 +1403,7 @@ Removed
     * ``Py_TRASHCAN_SAFE_BEGIN``
     * ``Py_TRASHCAN_SAFE_END``
 
-  * Move following functions and definitions to the internal C API:
+  * Moved following functions and definitions to the internal C API:
 
     * ``_PyDebug_PrintTotalRefs()``
     * ``_Py_PrintReferences()``
@@ -1185,12 +1413,12 @@ Removed
 
   (Contributed by Victor Stinner in :issue:`38644` and :issue:`39542`.)
 
-* Remove ``_PyRuntime.getframe`` hook and remove ``_PyThreadState_GetFrame``
+* Removed ``_PyRuntime.getframe`` hook and removed ``_PyThreadState_GetFrame``
   macro which was an alias to ``_PyRuntime.getframe``. They were only exposed
-  by the internal C API. Remove also ``PyThreadFrameGetter`` type.
+  by the internal C API. Removed also ``PyThreadFrameGetter`` type.
   (Contributed by Victor Stinner in :issue:`39946`.)
 
-* Remove the following functions from the C API. Call :c:func:`PyGC_Collect`
+* Removed the following functions from the C API. Call :c:func:`PyGC_Collect`
   explicitly to clear all free lists.
   (Contributed by Inada Naoki and Victor Stinner in :issue:`37340`,
   :issue:`38896` and :issue:`40428`.)
@@ -1209,10 +1437,20 @@ Removed
   * ``PyUnicode_ClearFreeList()``: the Unicode free list has been removed in
     Python 3.3.
 
-* Remove ``_PyUnicode_ClearStaticStrings()`` function.
+* Removed ``_PyUnicode_ClearStaticStrings()`` function.
   (Contributed by Victor Stinner in :issue:`39465`.)
 
-* Remove ``Py_UNICODE_MATCH``. It has been deprecated by :pep:`393`, and
+* Removed ``Py_UNICODE_MATCH``. It has been deprecated by :pep:`393`, and
   broken since Python 3.3. The :c:func:`PyUnicode_Tailmatch` function can be
   used instead.
   (Contributed by Inada Naoki in :issue:`36346`.)
+
+* Cleaned header files of interfaces defined but with no implementation.
+  The public API symbols being removed are:
+  ``_PyBytes_InsertThousandsGroupingLocale``,
+  ``_PyBytes_InsertThousandsGrouping``, ``_Py_InitializeFromArgs``,
+  ``_Py_InitializeFromWideArgs``, ``_PyFloat_Repr``, ``_PyFloat_Digits``,
+  ``_PyFloat_DigitsInit``, ``PyFrame_ExtendStack``, ``_PyAIterWrapper_Type``,
+  ``PyNullImporter_Type``, ``PyCmpWrapper_Type``, ``PySortWrapper_Type``,
+  ``PyNoArgsFunction``.
+  (Contributed by Pablo Galindo Salgado in :issue:`39372`.)

Grammar/python.gram

@@ -428,7 +428,7 @@ compare_op_bitwise_or_pair[CmpopExprPair*]:
     | is_bitwise_or
 eq_bitwise_or[CmpopExprPair*]: '==' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Eq, a) }
 noteq_bitwise_or[CmpopExprPair*]:
-    | (tok='!=' {_PyPegen_check_barry_as_flufl(p) ? NULL : tok}) a=bitwise_or {_PyPegen_cmpop_expr_pair(p, NotEq, a) }
+    | (tok='!=' { _PyPegen_check_barry_as_flufl(p, tok) ? NULL : tok}) a=bitwise_or {_PyPegen_cmpop_expr_pair(p, NotEq, a) }
 lte_bitwise_or[CmpopExprPair*]: '<=' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, LtE, a) }
 lt_bitwise_or[CmpopExprPair*]: '<' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Lt, a) }
 gte_bitwise_or[CmpopExprPair*]: '>=' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, GtE, a) }
@@ -475,6 +475,7 @@ await_primary[expr_ty] (memo):
     | AWAIT a=primary { CHECK_VERSION(expr_ty, 5, "Await expressions are", _Py_Await(a, EXTRA)) }
     | primary
 primary[expr_ty]:
+    | invalid_primary  # must be before 'primay genexp' because of invalid_genexp
     | a=primary '.' b=NAME { _Py_Attribute(a, b->v.Name.id, Load, EXTRA) }
     | a=primary b=genexp { _Py_Call(a, CHECK(asdl_expr_seq*, (asdl_expr_seq*)_PyPegen_singleton_seq(p, b)), NULL, EXTRA) }
     | a=primary '(' b=[arguments] ')' {
@@ -551,7 +552,7 @@ yield_expr[expr_ty]:
 
 arguments[expr_ty] (memo):
     | a=args [','] &')' { a }
-    | incorrect_arguments
+    | invalid_arguments
 args[expr_ty]:
     | a[asdl_expr_seq*]=','.(starred_expression | named_expression !'=')+ b=[',' k=kwargs {k}] { _PyPegen_collect_call_seqs(p, a, b, EXTRA) }
     | a=kwargs { _Py_Call(_PyPegen_dummy_name(p),
@@ -637,7 +638,7 @@ t_atom[expr_ty]:
 
 
 # From here on, there are rules for invalid syntax with specialised error messages
-incorrect_arguments:
+invalid_arguments:
     | args ',' '*' { RAISE_SYNTAX_ERROR("iterable argument unpacking follows keyword argument unpacking") }
     | a=expression for_if_clauses ',' [args | expression for_if_clauses] {
         RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "Generator expression must be parenthesized") }
@@ -682,6 +683,8 @@ invalid_del_stmt:
         RAISE_SYNTAX_ERROR_INVALID_TARGET(DEL_TARGETS, a) }
 invalid_block:
     | NEWLINE !INDENT { RAISE_INDENTATION_ERROR("expected an indented block") }
+invalid_primary:
+    | primary a='{' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "invalid syntax") }
 invalid_comprehension:
     | ('[' | '(' | '{') a=starred_expression for_if_clauses {
         RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "iterable unpacking cannot be used in comprehension") }

Include/Python-ast.h

@@ -1,4 +1,4 @@
-/* File automatically generated by Parser/asdl_c.py. */
+// File automatically generated by Parser/asdl_c.py.
 
 #ifndef Py_PYTHON_AST_H
 #define Py_PYTHON_AST_H

Include/boolobject.h

@@ -22,8 +22,8 @@ PyAPI_DATA(struct _longobject) _Py_FalseStruct, _Py_TrueStruct;
 #define Py_True ((PyObject *) &_Py_TrueStruct)
 
 /* Macros for returning Py_True or Py_False, respectively */
-#define Py_RETURN_TRUE return Py_INCREF(Py_True), Py_True
-#define Py_RETURN_FALSE return Py_INCREF(Py_False), Py_False
+#define Py_RETURN_TRUE return Py_NewRef(Py_True)
+#define Py_RETURN_FALSE return Py_NewRef(Py_False)
 
 /* Function to return a bool from a C long */
 PyAPI_FUNC(PyObject *) PyBool_FromLong(long);

Include/cpython/dictobject.h

@@ -46,7 +46,8 @@ PyAPI_FUNC(int) _PyDict_Next(
 
 /* Get the number of items of a dictionary. */
 #define PyDict_GET_SIZE(mp)  (assert(PyDict_Check(mp)),((PyDictObject *)mp)->ma_used)
-PyAPI_FUNC(int) _PyDict_Contains(PyObject *mp, PyObject *key, Py_hash_t hash);
+PyAPI_FUNC(int) _PyDict_Contains_KnownHash(PyObject *, PyObject *, Py_hash_t);
+PyAPI_FUNC(int) _PyDict_ContainsId(PyObject *, struct _Py_Identifier *);
 PyAPI_FUNC(PyObject *) _PyDict_NewPresized(Py_ssize_t minused);
 PyAPI_FUNC(void) _PyDict_MaybeUntrack(PyObject *mp);
 PyAPI_FUNC(int) _PyDict_HasOnlyStringKeys(PyObject *mp);
@@ -63,7 +64,6 @@ PyObject *_PyDict_FromKeys(PyObject *, PyObject *, PyObject *);
    argument is raised.
 */
 PyAPI_FUNC(int) _PyDict_MergeEx(PyObject *mp, PyObject *other, int override);
-PyAPI_FUNC(PyObject *) _PyDict_GetItemId(PyObject *dp, struct _Py_Identifier *key);
 PyAPI_FUNC(int) _PyDict_SetItemId(PyObject *dp, struct _Py_Identifier *key, PyObject *item);
 
 PyAPI_FUNC(int) _PyDict_DelItemId(PyObject *mp, struct _Py_Identifier *key);

Include/cpython/initconfig.h

@@ -41,7 +41,7 @@ PyAPI_FUNC(PyStatus) PyWideStringList_Insert(PyWideStringList *list,
 
 /* --- PyPreConfig ----------------------------------------------- */
 
-typedef struct {
+typedef struct PyPreConfig {
     int _config_init;     /* _PyConfigInitEnum value */
 
     /* Parse Py_PreInitializeFromBytesArgs() arguments?
@@ -127,296 +127,84 @@ PyAPI_FUNC(void) PyPreConfig_InitIsolatedConfig(PyPreConfig *config);
 
 /* --- PyConfig ---------------------------------------------- */
 
-typedef struct {
+/* This structure is best documented in the Doc/c-api/init_config.rst file. */
+typedef struct PyConfig {
     int _config_init;     /* _PyConfigInitEnum value */
 
-    int isolated;         /* Isolated mode? see PyPreConfig.isolated */
-    int use_environment;  /* Use environment variables? see PyPreConfig.use_environment */
-    int dev_mode;         /* Python Development Mode? See PyPreConfig.dev_mode */
-
-    /* Install signal handlers? Yes by default. */
+    int isolated;
+    int use_environment;
+    int dev_mode;
     int install_signal_handlers;
-
-    int use_hash_seed;      /* PYTHONHASHSEED=x */
+    int use_hash_seed;
     unsigned long hash_seed;
-
-    /* Enable faulthandler?
-       Set to 1 by -X faulthandler and PYTHONFAULTHANDLER. -1 means unset. */
     int faulthandler;
-
-    /* Enable tracemalloc?
-       Set by -X tracemalloc=N and PYTHONTRACEMALLOC. -1 means unset */
     int tracemalloc;
-
-    int import_time;        /* PYTHONPROFILEIMPORTTIME, -X importtime */
-    int show_ref_count;     /* -X showrefcount */
-    int dump_refs;          /* PYTHONDUMPREFS */
-    int malloc_stats;       /* PYTHONMALLOCSTATS */
-
-    /* Python filesystem encoding and error handler:
-       sys.getfilesystemencoding() and sys.getfilesystemencodeerrors().
-
-       Default encoding and error handler:
-
-       * if Py_SetStandardStreamEncoding() has been called: they have the
-         highest priority;
-       * PYTHONIOENCODING environment variable;
-       * The UTF-8 Mode uses UTF-8/surrogateescape;
-       * If Python forces the usage of the ASCII encoding (ex: C locale
-         or POSIX locale on FreeBSD or HP-UX), use ASCII/surrogateescape;
-       * locale encoding: ANSI code page on Windows, UTF-8 on Android and
-         VxWorks, LC_CTYPE locale encoding on other platforms;
-       * On Windows, "surrogateescape" error handler;
-       * "surrogateescape" error handler if the LC_CTYPE locale is "C" or "POSIX";
-       * "surrogateescape" error handler if the LC_CTYPE locale has been coerced
-         (PEP 538);
-       * "strict" error handler.
-
-       Supported error handlers: "strict", "surrogateescape" and
-       "surrogatepass". The surrogatepass error handler is only supported
-       if Py_DecodeLocale() and Py_EncodeLocale() use directly the UTF-8 codec;
-       it's only used on Windows.
-
-       initfsencoding() updates the encoding to the Python codec name.
-       For example, "ANSI_X3.4-1968" is replaced with "ascii".
-
-       On Windows, sys._enablelegacywindowsfsencoding() sets the
-       encoding/errors to mbcs/replace at runtime.
-
-
-       See Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors.
-       */
+    int import_time;
+    int show_ref_count;
+    int dump_refs;
+    int malloc_stats;
     wchar_t *filesystem_encoding;
     wchar_t *filesystem_errors;
-
-    wchar_t *pycache_prefix;  /* PYTHONPYCACHEPREFIX, -X pycache_prefix=PATH */
-    int parse_argv;           /* Parse argv command line arguments? */
-
-    /* Command line arguments (sys.argv).
-
-       Set parse_argv to 1 to parse argv as Python command line arguments
-       and then strip Python arguments from argv.
-
-       If argv is empty, an empty string is added to ensure that sys.argv
-       always exists and is never empty. */
+    wchar_t *pycache_prefix;
+    int parse_argv;
+    PyWideStringList orig_argv;
     PyWideStringList argv;
-
-    /* Program name:
-
-       - If Py_SetProgramName() was called, use its value.
-       - On macOS, use PYTHONEXECUTABLE environment variable if set.
-       - If WITH_NEXT_FRAMEWORK macro is defined, use __PYVENV_LAUNCHER__
-         environment variable is set.
-       - Use argv[0] if available and non-empty.
-       - Use "python" on Windows, or "python3 on other platforms. */
-    wchar_t *program_name;
-
-    PyWideStringList xoptions;     /* Command line -X options */
-
-    /* Warnings options: lowest to highest priority. warnings.filters
-       is built in the reverse order (highest to lowest priority). */
+    PyWideStringList xoptions;
     PyWideStringList warnoptions;
-
-    /* If equal to zero, disable the import of the module site and the
-       site-dependent manipulations of sys.path that it entails. Also disable
-       these manipulations if site is explicitly imported later (call
-       site.main() if you want them to be triggered).
-
-       Set to 0 by the -S command line option. If set to -1 (default), it is
-       set to !Py_NoSiteFlag. */
     int site_import;
-
-    /* Bytes warnings:
-
-       * If equal to 1, issue a warning when comparing bytes or bytearray with
-         str or bytes with int.
-       * If equal or greater to 2, issue an error.
-
-       Incremented by the -b command line option. If set to -1 (default), inherit
-       Py_BytesWarningFlag value. */
     int bytes_warning;
-
-    /* If greater than 0, enable inspect: when a script is passed as first
-       argument or the -c option is used, enter interactive mode after
-       executing the script or the command, even when sys.stdin does not appear
-       to be a terminal.
-
-       Incremented by the -i command line option. Set to 1 if the PYTHONINSPECT
-       environment variable is non-empty. If set to -1 (default), inherit
-       Py_InspectFlag value. */
     int inspect;
-
-    /* If greater than 0: enable the interactive mode (REPL).
-
-       Incremented by the -i command line option. If set to -1 (default),
-       inherit Py_InteractiveFlag value. */
     int interactive;
-
-    /* Optimization level.
-
-       Incremented by the -O command line option. Set by the PYTHONOPTIMIZE
-       environment variable. If set to -1 (default), inherit Py_OptimizeFlag
-       value. */
     int optimization_level;
-
-    /* If greater than 0, enable the debug mode: turn on parser debugging
-       output (for expert only, depending on compilation options).
-
-       Incremented by the -d command line option. Set by the PYTHONDEBUG
-       environment variable. If set to -1 (default), inherit Py_DebugFlag
-       value. */
     int parser_debug;
-
-    /* If equal to 0, Python won't try to write ``.pyc`` files on the
-       import of source modules.
-
-       Set to 0 by the -B command line option and the PYTHONDONTWRITEBYTECODE
-       environment variable. If set to -1 (default), it is set to
-       !Py_DontWriteBytecodeFlag. */
     int write_bytecode;
-
-    /* If greater than 0, enable the verbose mode: print a message each time a
-       module is initialized, showing the place (filename or built-in module)
-       from which it is loaded.
-
-       If greater or equal to 2, print a message for each file that is checked
-       for when searching for a module. Also provides information on module
-       cleanup at exit.
-
-       Incremented by the -v option. Set by the PYTHONVERBOSE environment
-       variable. If set to -1 (default), inherit Py_VerboseFlag value. */
     int verbose;
-
-    /* If greater than 0, enable the quiet mode: Don't display the copyright
-       and version messages even in interactive mode.
-
-       Incremented by the -q option. If set to -1 (default), inherit
-       Py_QuietFlag value. */
     int quiet;
-
-   /* If greater than 0, don't add the user site-packages directory to
-      sys.path.
-
-      Set to 0 by the -s and -I command line options , and the PYTHONNOUSERSITE
-      environment variable. If set to -1 (default), it is set to
-      !Py_NoUserSiteDirectory. */
     int user_site_directory;
-
-    /* If non-zero, configure C standard steams (stdio, stdout,
-       stderr):
-
-       - Set O_BINARY mode on Windows.
-       - If buffered_stdio is equal to zero, make streams unbuffered.
-         Otherwise, enable streams buffering if interactive is non-zero. */
     int configure_c_stdio;
-
-    /* If equal to 0, enable unbuffered mode: force the stdout and stderr
-       streams to be unbuffered.
-
-       Set to 0 by the -u option. Set by the PYTHONUNBUFFERED environment
-       variable.
-       If set to -1 (default), it is set to !Py_UnbufferedStdioFlag. */
     int buffered_stdio;
-
-    /* Encoding of sys.stdin, sys.stdout and sys.stderr.
-       Value set from PYTHONIOENCODING environment variable and
-       Py_SetStandardStreamEncoding() function.
-       See also 'stdio_errors' attribute. */
     wchar_t *stdio_encoding;
-
-    /* Error handler of sys.stdin and sys.stdout.
-       Value set from PYTHONIOENCODING environment variable and
-       Py_SetStandardStreamEncoding() function.
-       See also 'stdio_encoding' attribute. */
     wchar_t *stdio_errors;
-
 #ifdef MS_WINDOWS
-    /* If greater than zero, use io.FileIO instead of WindowsConsoleIO for sys
-       standard streams.
-
-       Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to
-       a non-empty string. If set to -1 (default), inherit
-       Py_LegacyWindowsStdioFlag value.
-
-       See PEP 528 for more details. */
     int legacy_windows_stdio;
 #endif
-
-    /* Value of the --check-hash-based-pycs command line option:
-
-       - "default" means the 'check_source' flag in hash-based pycs
-         determines invalidation
-       - "always" causes the interpreter to hash the source file for
-         invalidation regardless of value of 'check_source' bit
-       - "never" causes the interpreter to always assume hash-based pycs are
-         valid
-
-       The default value is "default".
-
-       See PEP 552 "Deterministic pycs" for more details. */
     wchar_t *check_hash_pycs_mode;
 
     /* --- Path configuration inputs ------------ */
-
-    /* If greater than 0, suppress _PyPathConfig_Calculate() warnings on Unix.
-       The parameter has no effect on Windows.
-
-       If set to -1 (default), inherit !Py_FrozenFlag value. */
     int pathconfig_warnings;
-
-    wchar_t *pythonpath_env; /* PYTHONPATH environment variable */
-    wchar_t *home;          /* PYTHONHOME environment variable,
-                               see also Py_SetPythonHome(). */
+    wchar_t *program_name;
+    wchar_t *pythonpath_env;
+    wchar_t *home;
+    wchar_t *platlibdir;
 
     /* --- Path configuration outputs ----------- */
-
-    int module_search_paths_set;  /* If non-zero, use module_search_paths */
-    PyWideStringList module_search_paths;  /* sys.path paths. Computed if
-                                       module_search_paths_set is equal
-                                       to zero. */
-
-    wchar_t *executable;        /* sys.executable */
-    wchar_t *base_executable;   /* sys._base_executable */
-    wchar_t *prefix;            /* sys.prefix */
-    wchar_t *base_prefix;       /* sys.base_prefix */
-    wchar_t *exec_prefix;       /* sys.exec_prefix */
-    wchar_t *base_exec_prefix;  /* sys.base_exec_prefix */
-    wchar_t *platlibdir;        /* sys.platlibdir */
+    int module_search_paths_set;
+    PyWideStringList module_search_paths;
+    wchar_t *executable;
+    wchar_t *base_executable;
+    wchar_t *prefix;
+    wchar_t *base_prefix;
+    wchar_t *exec_prefix;
+    wchar_t *base_exec_prefix;
 
     /* --- Parameter only used by Py_Main() ---------- */
-
-    /* Skip the first line of the source ('run_filename' parameter), allowing use of non-Unix forms of
-       "#!cmd".  This is intended for a DOS specific hack only.
-
-       Set by the -x command line option. */
     int skip_source_first_line;
-
-    wchar_t *run_command;   /* -c command line argument */
-    wchar_t *run_module;    /* -m command line argument */
-    wchar_t *run_filename;  /* Trailing command line argument without -c or -m */
+    wchar_t *run_command;
+    wchar_t *run_module;
+    wchar_t *run_filename;
 
     /* --- Private fields ---------------------------- */
 
-    /* Install importlib? If set to 0, importlib is not initialized at all.
-       Needed by freeze_importlib. */
+    // Install importlib? If equals to 0, importlib is not initialized at all.
+    // Needed by freeze_importlib.
     int _install_importlib;
 
-    /* If equal to 0, stop Python initialization before the "main" phase */
+    // If equal to 0, stop Python initialization before the "main" phase.
     int _init_main;
 
-    /* If non-zero, disallow threads, subprocesses, and fork.
-       Default: 0. */
+    // If non-zero, disallow threads, subprocesses, and fork.
+    // Default: 0.
     int _isolated_interpreter;
-
-    /* The list of the original command line arguments passed to the Python
-       executable.
-
-       If 'orig_argv' list is empty and 'argv' is not a list only containing an
-       empty string, PyConfig_Read() copies 'argv' into 'orig_argv' before
-       modifying 'argv' (if 'parse_argv is non-zero).
-
-       _PyConfig_Write() initializes Py_GetArgcArgv() to this list. */
-    PyWideStringList orig_argv;
 } PyConfig;
 
 PyAPI_FUNC(void) PyConfig_InitPythonConfig(PyConfig *config);

Include/cpython/object.h

@@ -296,6 +296,8 @@ PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, _Py_Identifier *);
 PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
 PyAPI_FUNC(PyObject *) _PyType_GetDocFromInternalDoc(const char *, const char *);
 PyAPI_FUNC(PyObject *) _PyType_GetTextSignatureFromInternalDoc(const char *, const char *);
+struct PyModuleDef;
+PyAPI_FUNC(PyObject *) _PyType_GetModuleByDef(PyTypeObject *, struct PyModuleDef *);
 
 struct _Py_Identifier;
 PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);

Include/cpython/objimpl.h

@@ -79,10 +79,6 @@ PyAPI_FUNC(void) PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator);
 PyAPI_FUNC(void) PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator);
 
 
-PyAPI_FUNC(Py_ssize_t) _PyGC_CollectNoFail(void);
-PyAPI_FUNC(Py_ssize_t) _PyGC_CollectIfEnabled(void);
-
-
 /* Test if an object implements the garbage collector protocol */
 PyAPI_FUNC(int) PyObject_IS_GC(PyObject *obj);
 

Include/cpython/pystate.h

@@ -167,6 +167,11 @@ PyAPI_FUNC(PyInterpreterState *) _PyGILState_GetInterpreterStateUnsafe(void);
 */
 PyAPI_FUNC(PyObject *) _PyThread_CurrentFrames(void);
 
+/* The implementation of sys._current_exceptions()  Returns a dict mapping
+   thread id to that thread's current exception.
+*/
+PyAPI_FUNC(PyObject *) _PyThread_CurrentExceptions(void);
+
 /* Routines for advanced debuggers, requested by David Beazley.
    Don't use unless you know what you are doing! */
 PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_Main(void);
@@ -188,6 +193,36 @@ PyAPI_FUNC(void) _PyInterpreterState_SetEvalFrameFunc(
 
 PyAPI_FUNC(const PyConfig*) _PyInterpreterState_GetConfig(PyInterpreterState *interp);
 
+/* Get a copy of the current interpreter configuration.
+
+   Return 0 on success. Raise an exception and return -1 on error.
+
+   The caller must initialize 'config', using PyConfig_InitPythonConfig()
+   for example.
+
+   Python must be preinitialized to call this method.
+   The caller must hold the GIL. */
+PyAPI_FUNC(int) _PyInterpreterState_GetConfigCopy(
+    struct PyConfig *config);
+
+/* Set the configuration of the current interpreter.
+
+   This function should be called during or just after the Python
+   initialization.
+
+   Update the sys module with the new configuration. If the sys module was
+   modified directly after the Python initialization, these changes are lost.
+
+   Some configuration like faulthandler or warnoptions can be updated in the
+   configuration, but don't reconfigure Python (don't enable/disable
+   faulthandler and don't reconfigure warnings filters).
+
+   Return 0 on success. Raise an exception and return -1 on error.
+
+   The configuration should come from _PyInterpreterState_GetConfigCopy(). */
+PyAPI_FUNC(int) _PyInterpreterState_SetConfig(
+    const struct PyConfig *config);
+
 // Get the configuration of the currrent interpreter.
 // The caller must hold the GIL.
 PyAPI_FUNC(const PyConfig*) _Py_GetConfig(void);

Include/internal/pycore_ast.h

@@ -0,0 +1,234 @@
+// File automatically generated by Parser/asdl_c.py.
+
+#ifndef Py_INTERNAL_AST_H
+#define Py_INTERNAL_AST_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+struct ast_state {
+    int initialized;
+    PyObject *AST_type;
+    PyObject *Add_singleton;
+    PyObject *Add_type;
+    PyObject *And_singleton;
+    PyObject *And_type;
+    PyObject *AnnAssign_type;
+    PyObject *Assert_type;
+    PyObject *Assign_type;
+    PyObject *AsyncFor_type;
+    PyObject *AsyncFunctionDef_type;
+    PyObject *AsyncWith_type;
+    PyObject *Attribute_type;
+    PyObject *AugAssign_type;
+    PyObject *Await_type;
+    PyObject *BinOp_type;
+    PyObject *BitAnd_singleton;
+    PyObject *BitAnd_type;
+    PyObject *BitOr_singleton;
+    PyObject *BitOr_type;
+    PyObject *BitXor_singleton;
+    PyObject *BitXor_type;
+    PyObject *BoolOp_type;
+    PyObject *Break_type;
+    PyObject *Call_type;
+    PyObject *ClassDef_type;
+    PyObject *Compare_type;
+    PyObject *Constant_type;
+    PyObject *Continue_type;
+    PyObject *Del_singleton;
+    PyObject *Del_type;
+    PyObject *Delete_type;
+    PyObject *DictComp_type;
+    PyObject *Dict_type;
+    PyObject *Div_singleton;
+    PyObject *Div_type;
+    PyObject *Eq_singleton;
+    PyObject *Eq_type;
+    PyObject *ExceptHandler_type;
+    PyObject *Expr_type;
+    PyObject *Expression_type;
+    PyObject *FloorDiv_singleton;
+    PyObject *FloorDiv_type;
+    PyObject *For_type;
+    PyObject *FormattedValue_type;
+    PyObject *FunctionDef_type;
+    PyObject *FunctionType_type;
+    PyObject *GeneratorExp_type;
+    PyObject *Global_type;
+    PyObject *GtE_singleton;
+    PyObject *GtE_type;
+    PyObject *Gt_singleton;
+    PyObject *Gt_type;
+    PyObject *IfExp_type;
+    PyObject *If_type;
+    PyObject *ImportFrom_type;
+    PyObject *Import_type;
+    PyObject *In_singleton;
+    PyObject *In_type;
+    PyObject *Interactive_type;
+    PyObject *Invert_singleton;
+    PyObject *Invert_type;
+    PyObject *IsNot_singleton;
+    PyObject *IsNot_type;
+    PyObject *Is_singleton;
+    PyObject *Is_type;
+    PyObject *JoinedStr_type;
+    PyObject *LShift_singleton;
+    PyObject *LShift_type;
+    PyObject *Lambda_type;
+    PyObject *ListComp_type;
+    PyObject *List_type;
+    PyObject *Load_singleton;
+    PyObject *Load_type;
+    PyObject *LtE_singleton;
+    PyObject *LtE_type;
+    PyObject *Lt_singleton;
+    PyObject *Lt_type;
+    PyObject *MatMult_singleton;
+    PyObject *MatMult_type;
+    PyObject *Mod_singleton;
+    PyObject *Mod_type;
+    PyObject *Module_type;
+    PyObject *Mult_singleton;
+    PyObject *Mult_type;
+    PyObject *Name_type;
+    PyObject *NamedExpr_type;
+    PyObject *Nonlocal_type;
+    PyObject *NotEq_singleton;
+    PyObject *NotEq_type;
+    PyObject *NotIn_singleton;
+    PyObject *NotIn_type;
+    PyObject *Not_singleton;
+    PyObject *Not_type;
+    PyObject *Or_singleton;
+    PyObject *Or_type;
+    PyObject *Pass_type;
+    PyObject *Pow_singleton;
+    PyObject *Pow_type;
+    PyObject *RShift_singleton;
+    PyObject *RShift_type;
+    PyObject *Raise_type;
+    PyObject *Return_type;
+    PyObject *SetComp_type;
+    PyObject *Set_type;
+    PyObject *Slice_type;
+    PyObject *Starred_type;
+    PyObject *Store_singleton;
+    PyObject *Store_type;
+    PyObject *Sub_singleton;
+    PyObject *Sub_type;
+    PyObject *Subscript_type;
+    PyObject *Try_type;
+    PyObject *Tuple_type;
+    PyObject *TypeIgnore_type;
+    PyObject *UAdd_singleton;
+    PyObject *UAdd_type;
+    PyObject *USub_singleton;
+    PyObject *USub_type;
+    PyObject *UnaryOp_type;
+    PyObject *While_type;
+    PyObject *With_type;
+    PyObject *YieldFrom_type;
+    PyObject *Yield_type;
+    PyObject *__dict__;
+    PyObject *__doc__;
+    PyObject *__module__;
+    PyObject *_attributes;
+    PyObject *_fields;
+    PyObject *alias_type;
+    PyObject *annotation;
+    PyObject *arg;
+    PyObject *arg_type;
+    PyObject *args;
+    PyObject *argtypes;
+    PyObject *arguments_type;
+    PyObject *asname;
+    PyObject *ast;
+    PyObject *attr;
+    PyObject *bases;
+    PyObject *body;
+    PyObject *boolop_type;
+    PyObject *cause;
+    PyObject *cmpop_type;
+    PyObject *col_offset;
+    PyObject *comparators;
+    PyObject *comprehension_type;
+    PyObject *context_expr;
+    PyObject *conversion;
+    PyObject *ctx;
+    PyObject *decorator_list;
+    PyObject *defaults;
+    PyObject *elt;
+    PyObject *elts;
+    PyObject *end_col_offset;
+    PyObject *end_lineno;
+    PyObject *exc;
+    PyObject *excepthandler_type;
+    PyObject *expr_context_type;
+    PyObject *expr_type;
+    PyObject *finalbody;
+    PyObject *format_spec;
+    PyObject *func;
+    PyObject *generators;
+    PyObject *handlers;
+    PyObject *id;
+    PyObject *ifs;
+    PyObject *is_async;
+    PyObject *items;
+    PyObject *iter;
+    PyObject *key;
+    PyObject *keys;
+    PyObject *keyword_type;
+    PyObject *keywords;
+    PyObject *kind;
+    PyObject *kw_defaults;
+    PyObject *kwarg;
+    PyObject *kwonlyargs;
+    PyObject *left;
+    PyObject *level;
+    PyObject *lineno;
+    PyObject *lower;
+    PyObject *mod_type;
+    PyObject *module;
+    PyObject *msg;
+    PyObject *name;
+    PyObject *names;
+    PyObject *op;
+    PyObject *operand;
+    PyObject *operator_type;
+    PyObject *ops;
+    PyObject *optional_vars;
+    PyObject *orelse;
+    PyObject *posonlyargs;
+    PyObject *returns;
+    PyObject *right;
+    PyObject *simple;
+    PyObject *slice;
+    PyObject *step;
+    PyObject *stmt_type;
+    PyObject *tag;
+    PyObject *target;
+    PyObject *targets;
+    PyObject *test;
+    PyObject *type;
+    PyObject *type_comment;
+    PyObject *type_ignore_type;
+    PyObject *type_ignores;
+    PyObject *unaryop_type;
+    PyObject *upper;
+    PyObject *value;
+    PyObject *values;
+    PyObject *vararg;
+    PyObject *withitem_type;
+};
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_AST_H */
+

Include/internal/pycore_fileutils.h

@@ -50,6 +50,9 @@ PyAPI_FUNC(int) _Py_GetLocaleconvNumeric(
 
 PyAPI_FUNC(void) _Py_closerange(int first, int last);
 
+PyAPI_FUNC(wchar_t*) _Py_GetLocaleEncoding(void);
+PyAPI_FUNC(PyObject*) _Py_GetLocaleEncodingObject(void);
+
 #ifdef __cplusplus
 }
 #endif

Include/internal/pycore_gc.h

@@ -161,7 +161,9 @@ struct _gc_runtime_state {
     Py_ssize_t long_lived_pending;
 };
 
-PyAPI_FUNC(void) _PyGC_InitState(struct _gc_runtime_state *);
+extern void _PyGC_InitState(struct _gc_runtime_state *);
+
+extern Py_ssize_t _PyGC_CollectNoFail(PyThreadState *tstate);
 
 
 // Functions to clear types free lists

Include/internal/pycore_initconfig.h

@@ -44,6 +44,8 @@ struct pyruntimestate;
 #define _PyStatus_UPDATE_FUNC(err) \
     do { err.func = _PyStatus_GET_FUNC(); } while (0)
 
+PyObject* _PyErr_SetFromPyStatus(PyStatus status);
+
 /* --- PyWideStringList ------------------------------------------------ */
 
 #define _PyWideStringList_INIT (PyWideStringList){.length = 0, .items = NULL}
@@ -150,12 +152,16 @@ extern PyStatus _PyConfig_Copy(
     PyConfig *config,
     const PyConfig *config2);
 extern PyStatus _PyConfig_InitPathConfig(PyConfig *config);
+extern PyStatus _PyConfig_Read(PyConfig *config, int compute_path_config);
 extern PyStatus _PyConfig_Write(const PyConfig *config,
     struct pyruntimestate *runtime);
 extern PyStatus _PyConfig_SetPyArgv(
     PyConfig *config,
     const _PyArgv *args);
 
+PyAPI_FUNC(PyObject*) _PyConfig_AsDict(const PyConfig *config);
+PyAPI_FUNC(int) _PyConfig_FromDict(PyConfig *config, PyObject *dict);
+
 
 /* --- Function used for testing ---------------------------------- */
 

Include/internal/pycore_interp.h

@@ -8,10 +8,11 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
-#include "pycore_atomic.h"    /* _Py_atomic_address */
-#include "pycore_gil.h"       /* struct _gil_runtime_state  */
-#include "pycore_gc.h"        /* struct _gc_runtime_state */
-#include "pycore_warnings.h"  /* struct _warnings_runtime_state */
+#include "pycore_atomic.h"        // _Py_atomic_address
+#include "pycore_ast.h"           // struct ast_state
+#include "pycore_gil.h"           // struct _gil_runtime_state
+#include "pycore_gc.h"            // struct _gc_runtime_state
+#include "pycore_warnings.h"      // struct _warnings_runtime_state
 
 struct _pending_calls {
     PyThread_type_lock lock;
@@ -163,6 +164,11 @@ struct _Py_exc_state {
 #define _PY_NSMALLPOSINTS           257
 #define _PY_NSMALLNEGINTS           5
 
+// _PyLong_GetZero() and _PyLong_GetOne() must always be available
+#if _PY_NSMALLPOSINTS < 2
+#  error "_PY_NSMALLPOSINTS must be greater than 1"
+#endif
+
 // The PyInterpreterState typedef is in Include/pystate.h.
 struct _is {
 
@@ -233,14 +239,12 @@ struct _is {
 
     PyObject *audit_hooks;
 
-#if _PY_NSMALLNEGINTS + _PY_NSMALLPOSINTS > 0
     /* Small integers are preallocated in this array so that they
        can be shared.
        The integers that are preallocated are those in the range
        -_PY_NSMALLNEGINTS (inclusive) to _PY_NSMALLPOSINTS (not inclusive).
     */
     PyLongObject* small_ints[_PY_NSMALLNEGINTS + _PY_NSMALLPOSINTS];
-#endif
     struct _Py_bytes_state bytes;
     struct _Py_unicode_state unicode;
     struct _Py_float_state float_state;
@@ -255,15 +259,12 @@ struct _is {
     struct _Py_async_gen_state async_gen;
     struct _Py_context_state context;
     struct _Py_exc_state exc_state;
+
+    struct ast_state ast;
 };
 
-/* Used by _PyImport_Cleanup() */
 extern void _PyInterpreterState_ClearModules(PyInterpreterState *interp);
-
-extern PyStatus _PyInterpreterState_SetConfig(
-    PyInterpreterState *interp,
-    const PyConfig *config);
-
+extern void _PyInterpreterState_Clear(PyThreadState *tstate);
 
 
 /* cross-interpreter data registry */

Include/internal/pycore_long.h

@@ -0,0 +1,43 @@
+#ifndef Py_INTERNAL_LONG_H
+#define Py_INTERNAL_LONG_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+#include "pycore_interp.h"        // PyInterpreterState.small_ints
+#include "pycore_pystate.h"       // _PyThreadState_GET()
+
+// Don't call this function but _PyLong_GetZero() and _PyLong_GetOne()
+static inline PyObject* __PyLong_GetSmallInt_internal(int value)
+{
+    PyThreadState *tstate = _PyThreadState_GET();
+#ifdef Py_DEBUG
+    _Py_EnsureTstateNotNULL(tstate);
+#endif
+    assert(-_PY_NSMALLNEGINTS <= value && value < _PY_NSMALLPOSINTS);
+    size_t index = _PY_NSMALLNEGINTS + value;
+    PyObject *obj = (PyObject*)tstate->interp->small_ints[index];
+    // _PyLong_GetZero() and _PyLong_GetOne() must not be called
+    // before _PyLong_Init() nor after _PyLong_Fini()
+    assert(obj != NULL);
+    return obj;
+}
+
+// Return a borrowed reference to the zero singleton.
+// The function cannot return NULL.
+static inline PyObject* _PyLong_GetZero(void)
+{ return __PyLong_GetSmallInt_internal(0); }
+
+// Return a borrowed reference to the one singleton.
+// The function cannot return NULL.
+static inline PyObject* _PyLong_GetOne(void)
+{ return __PyLong_GetSmallInt_internal(1); }
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_LONG_H */

Include/internal/pycore_pylifecycle.h

@@ -44,7 +44,7 @@ extern PyStatus _PySys_Create(
     PyObject **sysmod_p);
 extern PyStatus _PySys_ReadPreinitWarnOptions(PyWideStringList *options);
 extern PyStatus _PySys_ReadPreinitXOptions(PyConfig *config);
-extern int _PySys_InitMain(PyThreadState *tstate);
+extern int _PySys_UpdateConfig(PyThreadState *tstate);
 extern PyStatus _PyExc_Init(PyThreadState *tstate);
 extern PyStatus _PyErr_Init(void);
 extern PyStatus _PyBuiltins_AddExceptions(PyObject * bltinmod);
@@ -84,7 +84,7 @@ extern void _PyFaulthandler_Fini(void);
 extern void _PyHash_Fini(void);
 extern void _PyTraceMalloc_Fini(void);
 extern void _PyWarnings_Fini(PyInterpreterState *interp);
-extern void _PyAST_Fini(PyThreadState *tstate);
+extern void _PyAST_Fini(PyInterpreterState *interp);
 
 extern PyStatus _PyGILState_Init(PyThreadState *tstate);
 extern void _PyGILState_Fini(PyThreadState *tstate);

Include/internal/pycore_ucnhash.h

@@ -0,0 +1,34 @@
+/* Unicode name database interface */
+#ifndef Py_INTERNAL_UCNHASH_H
+#define Py_INTERNAL_UCNHASH_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+/* revised ucnhash CAPI interface (exported through a "wrapper") */
+
+#define PyUnicodeData_CAPSULE_NAME "unicodedata._ucnhash_CAPI"
+
+typedef struct {
+
+    /* Get name for a given character code.
+       Returns non-zero if success, zero if not.
+       Does not set Python exceptions. */
+    int (*getname)(Py_UCS4 code, char* buffer, int buflen,
+                   int with_alias_and_seq);
+
+    /* Get character code for a given name.
+       Same error handling as for getname(). */
+    int (*getcode)(const char* name, int namelen, Py_UCS4* code,
+                   int with_named_seq);
+
+} _PyUnicode_Name_CAPI;
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_UCNHASH_H */

Include/internal/pycore_unionobject.h

@@ -10,6 +10,7 @@ extern "C" {
 
 PyAPI_FUNC(PyObject *) _Py_Union(PyObject *args);
 PyAPI_DATA(PyTypeObject) _Py_UnionType;
+PyAPI_FUNC(PyObject *) _Py_union_type_or(PyObject* self, PyObject* param);
 
 #ifdef __cplusplus
 }

Include/longobject.h

@@ -210,9 +210,6 @@ PyAPI_FUNC(PyObject *) _PyLong_GCD(PyObject *, PyObject *);
 #endif /* !Py_LIMITED_API */
 
 #ifndef Py_LIMITED_API
-PyAPI_DATA(PyObject *) _PyLong_Zero;
-PyAPI_DATA(PyObject *) _PyLong_One;
-
 PyAPI_FUNC(PyObject *) _PyLong_Rshift(PyObject *, size_t);
 PyAPI_FUNC(PyObject *) _PyLong_Lshift(PyObject *, size_t);
 #endif

Include/methodobject.h

@@ -73,7 +73,7 @@ PyAPI_FUNC(PyObject *) PyCMethod_New(PyMethodDef *, PyObject *,
 
 #define METH_COEXIST   0x0040
 
-#ifndef Py_LIMITED_API
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03100000
 #define METH_FASTCALL  0x0080
 #endif
 

Include/modsupport.h

@@ -136,7 +136,15 @@ PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywords(
 void _PyArg_Fini(void);
 #endif   /* Py_LIMITED_API */
 
-PyAPI_FUNC(int) PyModule_AddObject(PyObject *, const char *, PyObject *);
+// Add an attribute with name 'name' and value 'obj' to the module 'mod.
+// On success, return 0 on success.
+// On error, raise an exception and return -1.
+PyAPI_FUNC(int) PyModule_AddObjectRef(PyObject *mod, const char *name, PyObject *value);
+
+// Similar to PyModule_AddObjectRef() but steal a reference to 'obj'
+// (Py_DECREF(obj)) on success (if it returns 0).
+PyAPI_FUNC(int) PyModule_AddObject(PyObject *mod, const char *, PyObject *value);
+
 PyAPI_FUNC(int) PyModule_AddIntConstant(PyObject *, const char *, long);
 PyAPI_FUNC(int) PyModule_AddStringConstant(PyObject *, const char *, const char *);
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03090000

Include/object.h

@@ -526,6 +526,32 @@ they can have object code that is not dependent on Python compilation flags.
 PyAPI_FUNC(void) Py_IncRef(PyObject *);
 PyAPI_FUNC(void) Py_DecRef(PyObject *);
 
+// Create a new strong reference to an object:
+// increment the reference count of the object and return the object.
+PyAPI_FUNC(PyObject*) Py_NewRef(PyObject *obj);
+
+// Similar to Py_NewRef(), but the object can be NULL.
+PyAPI_FUNC(PyObject*) Py_XNewRef(PyObject *obj);
+
+static inline PyObject* _Py_NewRef(PyObject *obj)
+{
+    Py_INCREF(obj);
+    return obj;
+}
+
+static inline PyObject* _Py_XNewRef(PyObject *obj)
+{
+    Py_XINCREF(obj);
+    return obj;
+}
+
+// Py_NewRef() and Py_XNewRef() are exported as functions for the stable ABI.
+// Names overriden with macros by static inline functions for best
+// performances.
+#define Py_NewRef(obj) _Py_NewRef(obj)
+#define Py_XNewRef(obj) _Py_XNewRef(obj)
+
+
 /*
 _Py_NoneStruct is an object of undefined type which can be used in contexts
 where NULL (nil) is not suitable (since NULL often means 'error').
@@ -536,7 +562,7 @@ PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
 #define Py_None (&_Py_NoneStruct)
 
 /* Macro for returning Py_None from a function */
-#define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
+#define Py_RETURN_NONE return Py_NewRef(Py_None)
 
 /*
 Py_NotImplemented is a singleton used to signal that an operation is
@@ -546,8 +572,7 @@ PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 
 /* Macro for returning Py_NotImplemented from a function */
-#define Py_RETURN_NOTIMPLEMENTED \
-    return Py_INCREF(Py_NotImplemented), Py_NotImplemented
+#define Py_RETURN_NOTIMPLEMENTED return Py_NewRef(Py_NotImplemented)
 
 /* Rich comparison opcodes */
 #define Py_LT 0

Include/patchlevel.h

@@ -20,10 +20,10 @@
 #define PY_MINOR_VERSION        10
 #define PY_MICRO_VERSION        0
 #define PY_RELEASE_LEVEL        PY_RELEASE_LEVEL_ALPHA
-#define PY_RELEASE_SERIAL       1
+#define PY_RELEASE_SERIAL       2
 
 /* Version as a string */
-#define PY_VERSION              "3.10.0a1+"
+#define PY_VERSION              "3.10.0a2+"
 /*--end constants--*/
 
 /* Version as a single 4-byte hex number, e.g. 0x010502B2 == 1.5.2b2.

Include/pyport.h

@@ -841,12 +841,16 @@ extern _invalid_parameter_handler _Py_silent_invalid_parameter_handler;
 #endif
 
 #if defined(__ANDROID__) || defined(__VXWORKS__)
-   /* Ignore the locale encoding: force UTF-8 */
+   // Use UTF-8 as the locale encoding, ignore the LC_CTYPE locale.
+   // See _Py_GetLocaleEncoding(), PyUnicode_DecodeLocale()
+   // and PyUnicode_EncodeLocale().
 #  define _Py_FORCE_UTF8_LOCALE
 #endif
 
 #if defined(_Py_FORCE_UTF8_LOCALE) || defined(__APPLE__)
-   /* Use UTF-8 as filesystem encoding */
+   // Use UTF-8 as the filesystem encoding.
+   // See PyUnicode_DecodeFSDefaultAndSize(), PyUnicode_EncodeFSDefault(),
+   // Py_DecodeLocale() and Py_EncodeLocale().
 #  define _Py_FORCE_UTF8_FS_ENCODING
 #endif
 

Include/ucnhash.h

@@ -1,36 +0,0 @@
-/* Unicode name database interface */
-#ifndef Py_LIMITED_API
-#ifndef Py_UCNHASH_H
-#define Py_UCNHASH_H
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/* revised ucnhash CAPI interface (exported through a "wrapper") */
-
-#define PyUnicodeData_CAPSULE_NAME "unicodedata.ucnhash_CAPI"
-
-typedef struct {
-
-    /* Size of this struct */
-    int size;
-
-    /* Get name for a given character code.  Returns non-zero if
-       success, zero if not.  Does not set Python exceptions.
-       If self is NULL, data come from the default version of the database.
-       If it is not NULL, it should be a unicodedata.ucd_X_Y_Z object */
-    int (*getname)(PyObject *self, Py_UCS4 code, char* buffer, int buflen,
-                   int with_alias_and_seq);
-
-    /* Get character code for a given name.  Same error handling
-       as for getname. */
-    int (*getcode)(PyObject *self, const char* name, int namelen, Py_UCS4* code,
-                   int with_named_seq);
-
-} _PyUnicode_Name_CAPI;
-
-#ifdef __cplusplus
-}
-#endif
-#endif /* !Py_UCNHASH_H */
-#endif /* !Py_LIMITED_API */

Lib/_bootlocale.py

@@ -1,46 +0,0 @@
-"""A minimal subset of the locale module used at interpreter startup
-(imported by the _io module), in order to reduce startup time.
-
-Don't import directly from third-party code; use the `locale` module instead!
-"""
-
-import sys
-import _locale
-
-if sys.platform.startswith("win"):
-    def getpreferredencoding(do_setlocale=True):
-        if sys.flags.utf8_mode:
-            return 'UTF-8'
-        return _locale._getdefaultlocale()[1]
-else:
-    try:
-        _locale.CODESET
-    except AttributeError:
-        if hasattr(sys, 'getandroidapilevel'):
-            # On Android langinfo.h and CODESET are missing, and UTF-8 is
-            # always used in mbstowcs() and wcstombs().
-            def getpreferredencoding(do_setlocale=True):
-                return 'UTF-8'
-        else:
-            def getpreferredencoding(do_setlocale=True):
-                if sys.flags.utf8_mode:
-                    return 'UTF-8'
-                # This path for legacy systems needs the more complex
-                # getdefaultlocale() function, import the full locale module.
-                import locale
-                return locale.getpreferredencoding(do_setlocale)
-    else:
-        def getpreferredencoding(do_setlocale=True):
-            assert not do_setlocale
-            if sys.flags.utf8_mode:
-                return 'UTF-8'
-            result = _locale.nl_langinfo(_locale.CODESET)
-            if not result and sys.platform == 'darwin':
-                # nl_langinfo can return an empty string
-                # when the setting has an invalid value.
-                # Default to UTF-8 in that case because
-                # UTF-8 is the default charset on OSX and
-                # returning nothing will crash the
-                # interpreter.
-                result = 'UTF-8'
-            return result

Lib/_osx_support.py

@@ -110,6 +110,26 @@ def _get_system_version():
 
     return _SYSTEM_VERSION
 
+_SYSTEM_VERSION_TUPLE = None
+def _get_system_version_tuple():
+    """
+    Return the macOS system version as a tuple
+
+    The return value is safe to use to compare
+    two version numbers.
+    """
+    global _SYSTEM_VERSION_TUPLE
+    if _SYSTEM_VERSION_TUPLE is None:
+        osx_version = _get_system_version()
+        if osx_version:
+            try:
+                _SYSTEM_VERSION_TUPLE = tuple(int(i) for i in osx_version.split('.'))
+            except ValueError:
+                _SYSTEM_VERSION_TUPLE = ()
+
+    return _SYSTEM_VERSION_TUPLE
+   
+
 def _remove_original_values(_config_vars):
     """Remove original unmodified values for testing"""
     # This is needed for higher-level cross-platform tests of get_platform.
@@ -132,14 +152,18 @@ def _supports_universal_builds():
     # builds, in particular -isysroot and -arch arguments to the compiler. This
     # is in support of allowing 10.4 universal builds to run on 10.3.x systems.
 
-    osx_version = _get_system_version()
-    if osx_version:
-        try:
-            osx_version = tuple(int(i) for i in osx_version.split('.'))
-        except ValueError:
-            osx_version = ''
+    osx_version = _get_system_version_tuple()
     return bool(osx_version >= (10, 4)) if osx_version else False
 
+def _supports_arm64_builds():
+    """Returns True if arm64 builds are supported on this system"""
+    # There are two sets of systems supporting macOS/arm64 builds:
+    # 1. macOS 11 and later, unconditionally
+    # 2. macOS 10.15 with Xcode 12.2 or later
+    # For now the second category is ignored.
+    osx_version = _get_system_version_tuple()
+    return osx_version >= (11, 0) if osx_version else False
+
 
 def _find_appropriate_compiler(_config_vars):
     """Find appropriate C compiler for extension module builds"""
@@ -331,6 +355,12 @@ def compiler_fixup(compiler_so, cc_args):
             except ValueError:
                 break
 
+    elif not _supports_arm64_builds():
+        # Look for "-arch arm64" and drop that
+        for idx in range(len(compiler_so)):
+            if compiler_so[idx] == '-arch' and compiler_so[idx+1] == "arm64":
+                del compiler_so[idx:idx+2]
+
     if 'ARCHFLAGS' in os.environ and not stripArch:
         # User specified different -arch flags in the environ,
         # see also distutils.sysconfig
@@ -481,6 +511,8 @@ def get_platform_osx(_config_vars, osname, release, machine):
 
             if len(archs) == 1:
                 machine = archs[0]
+            elif archs == ('arm64', 'x86_64'):
+                machine = 'universal2'
             elif archs == ('i386', 'ppc'):
                 machine = 'fat'
             elif archs == ('i386', 'x86_64'):

Lib/asyncio/base_futures.py

@@ -1,6 +1,7 @@
 __all__ = ()
 
 import reprlib
+from _thread import get_ident
 
 from . import format_helpers
 
@@ -41,6 +42,16 @@ def _format_callbacks(cb):
     return f'cb=[{cb}]'
 
 
+# bpo-42183: _repr_running is needed for repr protection
+# when a Future or Task result contains itself directly or indirectly.
+# The logic is borrowed from @reprlib.recursive_repr decorator.
+# Unfortunately, the direct decorator usage is impossible because of
+# AttributeError: '_asyncio.Task' object has no attribute '__module__' error.
+#
+# After fixing this thing we can return to the decorator based approach.
+_repr_running = set()
+
+
 def _future_repr_info(future):
     # (Future) -> str
     """helper function for Future.__repr__"""
@@ -49,9 +60,17 @@ def _future_repr_info(future):
         if future._exception is not None:
             info.append(f'exception={future._exception!r}')
         else:
-            # use reprlib to limit the length of the output, especially
-            # for very long strings
-            result = reprlib.repr(future._result)
+            key = id(future), get_ident()
+            if key in _repr_running:
+                result = '...'
+            else:
+                _repr_running.add(key)
+                try:
+                    # use reprlib to limit the length of the output, especially
+                    # for very long strings
+                    result = reprlib.repr(future._result)
+                finally:
+                    _repr_running.discard(key)
             info.append(f'result={result}')
     if future._callbacks:
         info.append(_format_callbacks(future._callbacks))

Lib/asyncio/tasks.py

@@ -373,7 +373,7 @@ ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
 async def wait(fs, *, loop=None, timeout=None, return_when=ALL_COMPLETED):
     """Wait for the Futures and coroutines given by fs to complete.
 
-    The sequence futures must not be empty.
+    The fs iterable must not be empty.
 
     Coroutines will be wrapped in Tasks.
 
@@ -573,7 +573,7 @@ def as_completed(fs, *, loop=None, timeout=None):
     Note: The futures 'f' are not necessarily members of fs.
     """
     if futures.isfuture(fs) or coroutines.iscoroutine(fs):
-        raise TypeError(f"expect a list of futures, not {type(fs).__name__}")
+        raise TypeError(f"expect an iterable of futures, not {type(fs).__name__}")
 
     from .queues import Queue  # Import here to avoid circular import problem.
     done = Queue(loop=loop)

Lib/binhex.py

@@ -117,12 +117,12 @@ class _Hqxcoderengine:
         first = 0
         while first <= len(self.hqxdata) - self.linelen:
             last = first + self.linelen
-            self.ofp.write(self.hqxdata[first:last] + b'\n')
+            self.ofp.write(self.hqxdata[first:last] + b'\r')
             self.linelen = LINELEN
             first = last
         self.hqxdata = self.hqxdata[first:]
         if force:
-            self.ofp.write(self.hqxdata + b':\n')
+            self.ofp.write(self.hqxdata + b':\r')
 
     def close(self):
         if self.data:

Lib/contextlib.py

@@ -80,6 +80,22 @@ class ContextDecorator(object):
         return inner
 
 
+class AsyncContextDecorator(object):
+    "A base class or mixin that enables async context managers to work as decorators."
+
+    def _recreate_cm(self):
+        """Return a recreated instance of self.
+        """
+        return self
+
+    def __call__(self, func):
+        @wraps(func)
+        async def inner(*args, **kwds):
+            async with self._recreate_cm():
+                return await func(*args, **kwds)
+        return inner
+
+
 class _GeneratorContextManagerBase:
     """Shared functionality for @contextmanager and @asynccontextmanager."""
 
@@ -167,9 +183,16 @@ class _GeneratorContextManager(_GeneratorContextManagerBase,
 
 
 class _AsyncGeneratorContextManager(_GeneratorContextManagerBase,
-                                    AbstractAsyncContextManager):
+                                    AbstractAsyncContextManager,
+                                    AsyncContextDecorator):
     """Helper for @asynccontextmanager."""
 
+    def _recreate_cm(self):
+        # _AGCM instances are one-shot context managers, so the
+        # ACM must be recreated each time a decorated function is
+        # called
+        return self.__class__(self.func, self.args, self.kwds)
+
     async def __aenter__(self):
         try:
             return await self.gen.__anext__()
@@ -303,6 +326,32 @@ class closing(AbstractContextManager):
         self.thing.close()
 
 
+class aclosing(AbstractAsyncContextManager):
+    """Async context manager for safely finalizing an asynchronously cleaned-up
+    resource such as an async generator, calling its ``aclose()`` method.
+
+    Code like this:
+
+        async with aclosing(<module>.fetch(<arguments>)) as agen:
+            <block>
+
+    is equivalent to this:
+
+        agen = <module>.fetch(<arguments>)
+        try:
+            <block>
+        finally:
+            await agen.aclose()
+
+    """
+    def __init__(self, thing):
+        self.thing = thing
+    async def __aenter__(self):
+        return self.thing
+    async def __aexit__(self, *exc_info):
+        await self.thing.aclose()
+
+
 class _RedirectStream(AbstractContextManager):
 
     _stream = None
@@ -655,7 +704,7 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
         return received_exc and suppressed_exc
 
 
-class nullcontext(AbstractContextManager):
+class nullcontext(AbstractContextManager, AbstractAsyncContextManager):
     """Context manager that does no additional processing.
 
     Used as a stand-in for a normal context manager, when a particular
@@ -674,3 +723,9 @@ class nullcontext(AbstractContextManager):
 
     def __exit__(self, *excinfo):
         pass
+
+    async def __aenter__(self):
+        return self.enter_result
+
+    async def __aexit__(self, *excinfo):
+        pass

Lib/copyreg.py

@@ -48,6 +48,7 @@ def _reconstructor(cls, base, state):
     return obj
 
 _HEAPTYPE = 1<<9
+_new_type = type(int.__new__)
 
 # Python code for object.__reduce_ex__ for protocols 0 and 1
 
@@ -57,6 +58,9 @@ def _reduce_ex(self, proto):
     for base in cls.__mro__:
         if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
             break
+        new = base.__new__
+        if isinstance(new, _new_type) and new.__self__ is base:
+            break
     else:
         base = object # not really reachable
     if base is object:

Lib/ctypes/macholib/dyld.py

@@ -6,6 +6,11 @@ import os
 from ctypes.macholib.framework import framework_info
 from ctypes.macholib.dylib import dylib_info
 from itertools import *
+try:
+    from _ctypes import _dyld_shared_cache_contains_path
+except ImportError:
+    def _dyld_shared_cache_contains_path(*args):
+        raise NotImplementedError
 
 __all__ = [
     'dyld_find', 'framework_find',
@@ -122,8 +127,15 @@ def dyld_find(name, executable_path=None, env=None):
                 dyld_executable_path_search(name, executable_path),
                 dyld_default_search(name, env),
             ), env):
+
         if os.path.isfile(path):
             return path
+        try:
+            if _dyld_shared_cache_contains_path(path):
+                return path
+        except NotImplementedError:
+            pass
+
     raise ValueError("dylib %s could not be found" % (name,))
 
 def framework_find(fn, executable_path=None, env=None):

Lib/ctypes/test/test_macholib.py

@@ -45,19 +45,22 @@ def find_lib(name):
 class MachOTest(unittest.TestCase):
     @unittest.skipUnless(sys.platform == "darwin", 'OSX-specific test')
     def test_find(self):
-
-        self.assertEqual(find_lib('pthread'),
-                             '/usr/lib/libSystem.B.dylib')
+        # On Mac OS 11, system dylibs are only present in the shared cache,
+        # so symlinks like libpthread.dylib -> libSystem.B.dylib will not
+        # be resolved by dyld_find
+        self.assertIn(find_lib('pthread'),
+                              ('/usr/lib/libSystem.B.dylib', '/usr/lib/libpthread.dylib'))
 
         result = find_lib('z')
         # Issue #21093: dyld default search path includes $HOME/lib and
         # /usr/local/lib before /usr/lib, which caused test failures if
         # a local copy of libz exists in one of them. Now ignore the head
         # of the path.
-        self.assertRegex(result, r".*/lib/libz\..*.*\.dylib")
+        self.assertRegex(result, r".*/lib/libz.*\.dylib")
 
-        self.assertEqual(find_lib('IOKit'),
-                             '/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit')
+        self.assertIn(find_lib('IOKit'),
+                              ('/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit',
+                              '/System/Library/Frameworks/IOKit.framework/IOKit'))
 
 if __name__ == "__main__":
     unittest.main()

Lib/distutils/tests/test_build_ext.py

@@ -493,7 +493,7 @@ class BuildExtTestCase(TempdirManager,
         # format the target value as defined in the Apple
         # Availability Macros.  We can't use the macro names since
         # at least one value we test with will not exist yet.
-        if target[1] < 10:
+        if target[:2] < (10, 10):
             # for 10.1 through 10.9.x -> "10n0"
             target = '%02d%01d0' % target
         else: