bpo-33592: Document the C API in PEP 567 (contextvars) (GH-7033)
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@ -113,5 +113,5 @@ Other Objects
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capsule.rst
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gen.rst
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coro.rst
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contextvars.rst
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datetime.rst
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@ -0,0 +1,125 @@
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.. highlightlang:: c
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.. _contextvarsobjects:
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Context Variables Objects
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-------------------------
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.. versionadded:: 3.7
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This section details the public C API for the :mod:`contextvars` module.
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.. c:type:: PyContext
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The C structure used to represent a :class:`contextvars.Context`
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object.
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.. c:type:: PyContextVar
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The C structure used to represent a :class:`contextvars.ContextVar`
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object.
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.. c:type:: PyContextToken
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The C structure used to represent a :class:`contextvars.Token` object.
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.. c:var:: PyTypeObject PyContext_Type
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The type object representing the *context* type.
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.. c:var:: PyTypeObject PyContextVar_Type
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The type object representing the *context variable* type.
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.. c:var:: PyTypeObject PyContextToken_Type
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The type object representing the *context variable token* type.
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Type-check macros:
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.. c:function:: int PyContext_CheckExact(PyObject *o)
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Return true if *o* is of type :c:data:`PyContext_Type`. *o* must not be
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*NULL*. This function always succeeds.
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.. c:function:: int PyContextVar_CheckExact(PyObject *o)
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Return true if *o* is of type :c:data:`PyContextVar_Type`. *o* must not be
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*NULL*. This function always succeeds.
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.. c:function:: int PyContextToken_CheckExact(PyObject *o)
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Return true if *o* is of type :c:data:`PyContextToken_Type`.
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*o* must not be *NULL*. This function always succeeds.
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Context object management functions:
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.. c:function:: PyContext *PyContext_New(void)
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Create a new empty context object. Returns ``NULL`` if an error
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has occurred.
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.. c:function:: PyContext *PyContext_Copy(PyContext *ctx)
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Create a shallow copy of the passed *ctx* context object.
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Returns ``NULL`` if an error has occurred.
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.. c:function:: PyContext *PyContext_CopyCurrent(void)
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Create a shallow copy of the current thread context.
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Returns ``NULL`` if an error has occurred.
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.. c:function:: int PyContext_Enter(PyContext *ctx)
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Set *ctx* as the current context for the current thread.
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Returns ``0`` on success, and ``-1`` on error.
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.. c:function:: int PyContext_Exit(PyContext *ctx)
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Deactivate the *ctx* context and restore the previous context as the
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current context for the current thread. Returns ``0`` on success,
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and ``-1`` on error.
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.. c:function:: int PyContext_ClearFreeList()
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Clear the context variable free list. Return the total number of
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freed items. This function always succeeds.
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Context variable functions:
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.. c:function:: PyContextVar *PyContextVar_New(const char *name, PyObject *def)
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Create a new ``ContextVar`` object. The *name* parameter is used
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for introspection and debug purposes. The *def* parameter may optionally
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specify the default value for the context variable. If an error has
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occurred, this function returns ``NULL``.
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.. c:function:: int PyContextVar_Get(PyContextVar *var, PyObject *default_value, PyObject **value)
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Get the value of a context variable. Returns ``-1`` if an error has
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occurred during lookup, and ``0`` if no error occurred, whether or not
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a value was found.
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If the context variable was found, *value* will be a pointer to it.
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If the context variable was *not* found, *value* will point to:
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- *default_value*, if not ``NULL``;
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- the default value of *var*, if not ``NULL``;
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- ``NULL``
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If the value was found, the function will create a new reference to it.
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.. c:function:: PyContextToken *PyContextVar_Set(PyContextVar *var, PyObject *value)
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Set the value of *var* to *value* in the current context. Returns a
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pointer to a :c:type:`PyContextToken` object, or ``NULL`` if an error
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has occurred.
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.. c:function:: int PyContextVar_Reset(PyContextVar *var, PyContextToken *token)
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Reset the state of the *var* context variable to that it was in before
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:c:func:`PyContextVar_Set` that returned the *token* was called.
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This function returns ``0`` on success and ``-1`` on error.
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@ -515,7 +515,8 @@ New Modules
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contextvars
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-----------
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The new :mod:`contextvars` module and a set of new C APIs introduce
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The new :mod:`contextvars` module and a set of
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:ref:`new C APIs <contextvarsobjects>` introduce
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support for *context variables*. Context variables are conceptually
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similar to thread-local variables. Unlike TLS, context variables
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support asynchronous code correctly.
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@ -1543,6 +1544,9 @@ A new API for thread-local storage has been implemented. See
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:ref:`thread-specific-storage-api` for a complete reference.
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(Contributed by Masayuki Yamamoto in :issue:`25658`.)
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The new :ref:`context variables <whatsnew37-pep567>` functionality
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exposes a number of :ref:`new C APIs <contextvarsobjects>`.
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The new :c:func:`PyImport_GetModule` function returns the previously
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imported module with the given name.
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(Contributed by Eric Snow in :issue:`28411`.)
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