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****************************
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What's New In Python 3.4
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****************************
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:Author: R. David Murray <rdmurray@bitdance.com> (Editor)
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.. Rules for maintenance:
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* Anyone can add text to this document, but the maintainer reserves the
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right to rewrite any additions. In particular, for obscure or esoteric
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features, the maintainer may reduce any addition to a simple reference to
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the new documentation rather than explaining the feature inline.
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* While the maintainer will periodically go through Misc/NEWS
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and add changes, it's best not to rely on this. We know from experience
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that any changes that aren't in the What's New documentation around the
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time of the original release will remain largely unknown to the community
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for years, even if they're added later. We also know from experience that
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other priorities can arise, and the maintainer will run out of time to do
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updates -- in such cases, end users will be much better served by partial
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notifications that at least give a hint about new features to
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investigate.
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* This is not a complete list of every single change; completeness
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is the purpose of Misc/NEWS. The What's New should focus on changes that
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are visible to Python *users* and that *require* a feature release (i.e.
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most bug fixes should only be recorded in Misc/NEWS)
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* PEPs should not be marked Final until they have an entry in What's New.
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A placeholder entry that is just a section header and a link to the PEP
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(e.g ":pep:`397` has been implemented") is acceptable. If a PEP has been
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implemented and noted in What's New, don't forget to mark it as Final!
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* If you want to draw your new text to the attention of the
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maintainer, add 'XXX' to the beginning of the paragraph or
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section.
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* It's OK to add just a very brief note about a change. For
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example: "The :ref:`~socket.transmogrify()` function was added to the
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:mod:`socket` module." The maintainer will research the change and
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write the necessary text (if appropriate). The advantage of doing this
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is that even if no more descriptive text is ever added, readers will at
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least have a notification that the new feature exists and a link to the
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relevant documentation.
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* You can comment out your additions if you like, but it's not
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necessary (especially when a final release is some months away).
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* Credit the author of a patch or bugfix. Just the name is
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sufficient; the e-mail address isn't necessary.
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* It's helpful to add the bug/patch number as a comment:
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The :ref:`~socket.transmogrify()` function was added to the
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:mod:`socket` module. (Contributed by P.Y. Developer in :issue:`12345`.)
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This saves the maintainer the effort of going through the Mercurial log
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when researching a change.
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* Cross referencing tip: :ref:`mod.attr` will display as ``mod.attr``,
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while :ref:`~mod.attr` will display as ``attr``.
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This article explains the new features in Python 3.4, compared to 3.3.
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Python 3.4 was released on March 16, 2014. For full details, see the
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`changelog <http://docs.python.org/3.4/whatsnew/changelog.html>`_.
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.. seealso::
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:pep:`429` -- Python 3.4 Release Schedule
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Summary -- Release Highlights
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=============================
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.. This section singles out the most important changes in Python 3.4.
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Brevity is key.
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New syntax features:
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* No new syntax features were added in Python 3.4.
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Other new features:
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* :ref:`pip should always be available <whatsnew-pep-453>` (:pep:`453`).
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* :ref:`Newly created file descriptors are non-inheritable <whatsnew-pep-446>`
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(:pep:`446`).
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* command line option for :ref:`isolated mode <whatsnew-isolated-mode>`
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(:issue:`16499`).
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* :ref:`improvements in the handling of codecs <codec-handling-improvements>`
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that are not text encodings (multiple issues).
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* :ref:`A ModuleSpec Type <whatsnew-pep-451>` for the Import System
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(:pep:`451`). (Affects importer authors.)
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* The :mod:`marshal` format has been made :ref:`more compact and efficient
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<whatsnew-marshal-3>` (:issue:`16475`).
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New library modules:
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* :mod:`asyncio`: :ref:`New provisional API for asynchronous IO
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<whatsnew-asyncio>` (:pep:`3156`).
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* :mod:`ensurepip`: :ref:`Bootstrapping the pip installer <whatsnew-ensurepip>`
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(:pep:`453`).
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* :mod:`enum`: :ref:`Support for enumeration types <whatsnew-enum>`
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(:pep:`435`).
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* :mod:`pathlib`: :ref:`Object-oriented filesystem paths <whatsnew-pathlib>`
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(:pep:`428`).
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* :mod:`selectors`: :ref:`High-level and efficient I/O multiplexing
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<whatsnew-selectors>`, built upon the :mod:`select` module primitives (part
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of :pep:`3156`).
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* :mod:`statistics`: A basic :ref:`numerically stable statistics library
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<whatsnew-statistics>` (:pep:`450`).
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* :mod:`tracemalloc`: :ref:`Trace Python memory allocations
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<whatsnew-tracemalloc>` (:pep:`454`).
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Significantly improved library modules:
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* :ref:`Single-dispatch generic functions <whatsnew-singledispatch>` in
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:mod:`functools` (:pep:`443`).
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* New :mod:`pickle` :ref:`protocol 4 <whatsnew-protocol-4>` (:pep:`3154`).
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* :mod:`multiprocessing` now has :ref:`an option to avoid using os.fork
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on Unix <whatsnew-multiprocessing-no-fork>` (:issue:`8713`).
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* :mod:`email` has a new submodule, :mod:`~email.contentmanager`, and
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a new :mod:`~email.message.Message` subclass
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(:class:`~email.contentmanager.EmailMessage`) that :ref:`simplify MIME
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handling <whatsnew_email_contentmanager>` (:issue:`18891`).
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* The :mod:`inspect` and :mod:`pydoc` modules are now capable of
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correct introspection of a much wider variety of callable objects,
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which improves the output of the Python :func:`help` system.
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* The :mod:`ipaddress` module API has been declared stable
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Security improvements:
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* :ref:`Secure and interchangeable hash algorithm <whatsnew-pep-456>`
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(:pep:`456`).
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* :ref:`Make newly created file descriptors non-inheritable <whatsnew-pep-446>`
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(:pep:`446`) to avoid leaking file descriptors to child processes.
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* New command line option for :ref:`isolated mode <whatsnew-isolated-mode>`,
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(:issue:`16499`).
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* :mod:`multiprocessing` now has :ref:`an option to avoid using os.fork
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on Unix <whatsnew-multiprocessing-no-fork>`. *spawn* and *forkserver* are
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more secure because they avoid sharing data with child processes.
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* :mod:`multiprocessing` child processes on Windows no longer inherit
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all of the parent's inheritable handles, only the necessary ones.
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* A new :func:`hashlib.pbkdf2_hmac` function provides
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the `PKCS#5 password-based key derivation function 2
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<http://en.wikipedia.org/wiki/PBKDF2>`_.
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* :ref:`TLSv1.1 and TLSv1.2 support <whatsnew-tls-11-12>` for :mod:`ssl`.
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* :ref:`Retrieving certificates from the Windows system cert store support
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<whatsnew34-win-cert-store>` for :mod:`ssl`.
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* :ref:`Server-side SNI (Server Name Indication) support
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<whatsnew34-sni>` for :mod:`ssl`.
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* The :class:`ssl.SSLContext` class has a :ref:`lot of improvements
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<whatsnew34-sslcontext>`.
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* All modules in the standard library that support SSL now support server
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certificate verification, including hostname matching
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(:func:`ssl.match_hostname`) and CRLs (Certificate Revocation lists, see
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:func:`ssl.SSLContext.load_verify_locations`).
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CPython implementation improvements:
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* :ref:`Safe object finalization <whatsnew-pep-442>` (:pep:`442`).
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* Leveraging :pep:`442`, in most cases :ref:`module globals are no longer set
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to None during finalization <whatsnew-pep-442>` (:issue:`18214`).
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* :ref:`Configurable memory allocators <whatsnew-pep-445>` (:pep:`445`).
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* :ref:`Argument Clinic <whatsnew-pep-436>` (:pep:`436`).
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Please read on for a comprehensive list of user-facing changes, including many
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other smaller improvements, CPython optimizations, deprecations, and potential
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porting issues.
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New Features
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============
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.. _whatsnew-pep-453:
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PEP 453: Explicit Bootstrapping of PIP in Python Installations
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--------------------------------------------------------------
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Bootstrapping pip By Default
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The new :mod:`ensurepip` module (defined in :pep:`453`) provides a standard
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cross-platform mechanism to bootstrap the pip installer into Python
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installations and virtual environments. The version of ``pip`` included
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with Python 3.4.0 is ``pip`` 1.5.4, and future 3.4.x maintenance releases
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will update the bundled version to the latest version of ``pip`` that is
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available at the time of creating the release candidate.
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By default, the commands ``pipX`` and ``pipX.Y`` will be installed on all
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platforms (where X.Y stands for the version of the Python installation),
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along with the ``pip`` Python package and its dependencies. On Windows and
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in virtual environments on all platforms, the unversioned ``pip`` command
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will also be installed. On other platforms, the system wide unversioned
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``pip`` command typically refers to the separately installed Python 2
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version.
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The :ref:`pyvenv <scripts-pyvenv>` command line utility and the :mod:`venv`
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module make use of the :mod:`ensurepip` module to make ``pip`` readily
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available in virtual environments. When using the command line utility,
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``pip`` is installed by default, while when using the :mod:`venv` module
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:ref:`venv-api` installation of ``pip`` must be requested explicitly.
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For CPython :ref:`source builds on POSIX systems <building-python-on-unix>`,
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the ``make install`` and ``make altinstall`` commands bootstrap ``pip`` by
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default. This behaviour can be controlled through configure options, and
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overridden through Makefile options.
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On Windows and Mac OS X, the CPython installers now default to installing
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``pip`` along with CPython itself (users may opt out of installing it
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during the installation process). Window users will need to opt in to the
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automatic ``PATH`` modifications to have ``pip`` available from the command
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line by default, otherwise it can still be accessed through the Python
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launcher for Windows as ``py -m pip``.
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As `discussed in the PEP`__, platform packagers may choose not to install
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these commands by default, as long as, when invoked, they provide clear and
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simple directions on how to install them on that platform (usually using
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the system package manager).
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__ http://www.python.org/dev/peps/pep-0453/#recommendations-for-downstream-distributors
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.. note::
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To avoid conflicts between parallel Python 2 and Python 3 installations,
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only the versioned ``pip3`` and ``pip3.4`` commands are bootstrapped by
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default when ``ensurepip`` is invoked directly - the ``--default-pip``
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option is needed to also request the unversioned ``pip`` command.
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``pyvenv`` and the Windows installer ensure that the unqualified ``pip``
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command is made available in those environments, and ``pip`` can always be
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invoked via the ``-m`` switch rather than directly to avoid ambiguity on
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systems with multiple Python installations.
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Documentation Changes
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~~~~~~~~~~~~~~~~~~~~~
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As part of this change, the :ref:`installing-index` and
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:ref:`distributing-index` sections of the documentation have been
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completely redesigned as short getting started and FAQ documents. Most
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packaging documentation has now been moved out to the Python Packaging
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Authority maintained `Python Packaging User Guide
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<http://packaging.python.org>`__ and the documentation of the individual
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projects.
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However, as this migration is currently still incomplete, the legacy
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versions of those guides remaining available as :ref:`install-index`
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and :ref:`distutils-index`.
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.. seealso::
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:pep:`453` -- Explicit bootstrapping of pip in Python installations
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PEP written by Donald Stufft and Nick Coghlan, implemented by
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Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.
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.. _whatsnew-pep-446:
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PEP 446: Newly Created File Descriptors Are Non-Inheritable
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-----------------------------------------------------------
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:pep:`446` makes newly created file descriptors :ref:`non-inheritable
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<fd_inheritance>`. In general, this is the behavior an application will
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want: when launching a new process, having currently open files also
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open in the new process can lead to all sorts of hard to find bugs,
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and potentially to security issues.
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However, there are occasions when inheritance is desired. To support
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these cases, the following new functions and methods are available:
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* :func:`os.get_inheritable`, :func:`os.set_inheritable`
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* :func:`os.get_handle_inheritable`, :func:`os.set_handle_inheritable`
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* :meth:`socket.socket.get_inheritable`, :meth:`socket.socket.set_inheritable`
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.. seealso::
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:pep:`446` -- Make newly created file descriptors non-inheritable
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PEP written and implemented by Victor Stinner.
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.. _codec-handling-improvements:
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Improvements to Codec Handling
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------------------------------
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Since it was first introduced, the :mod:`codecs` module has always been
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intended to operate as a type-neutral dynamic encoding and decoding
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system. However, its close coupling with the Python text model, especially
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the type restricted convenience methods on the builtin :class:`str`,
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:class:`bytes` and :class:`bytearray` types, has historically obscured that
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fact.
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As a key step in clarifying the situation, the :meth:`codecs.encode` and
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:meth:`codecs.decode` convenience functions are now properly documented in
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Python 2.7, 3.3 and 3.4. These functions have existed in the :mod:`codecs`
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module (and have been covered by the regression test suite) since Python 2.4,
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but were previously only discoverable through runtime introspection.
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Unlike the convenience methods on :class:`str`, :class:`bytes` and
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:class:`bytearray`, the :mod:`codecs` convenience functions support arbitrary
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codecs in both Python 2 and Python 3, rather than being limited to Unicode text
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encodings (in Python 3) or ``basestring`` <-> ``basestring`` conversions (in
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Python 2).
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In Python 3.4, the interpreter is able to identify the known non-text
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encodings provided in the standard library and direct users towards these
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general purpose convenience functions when appropriate::
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>>> b"abcdef".decode("hex")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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LookupError: 'hex' is not a text encoding; use codecs.decode() to handle arbitrary codecs
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>>> "hello".encode("rot13")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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LookupError: 'rot13' is not a text encoding; use codecs.encode() to handle arbitrary codecs
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>>> open("foo.txt", encoding="hex")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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LookupError: 'hex' is not a text encoding; use codecs.open() to handle arbitrary codecs
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In a related change, whenever it is feasible without breaking backwards
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compatibility, exceptions raised during encoding and decoding operations
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are wrapped in a chained exception of the same type that mentions the
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name of the codec responsible for producing the error::
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>>> import codecs
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>>> codecs.decode(b"abcdefgh", "hex")
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Traceback (most recent call last):
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File "/usr/lib/python3.4/encodings/hex_codec.py", line 20, in hex_decode
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return (binascii.a2b_hex(input), len(input))
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binascii.Error: Non-hexadecimal digit found
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The above exception was the direct cause of the following exception:
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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binascii.Error: decoding with 'hex' codec failed (Error: Non-hexadecimal digit found)
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>>> codecs.encode("hello", "bz2")
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Traceback (most recent call last):
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File "/usr/lib/python3.4/encodings/bz2_codec.py", line 17, in bz2_encode
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return (bz2.compress(input), len(input))
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File "/usr/lib/python3.4/bz2.py", line 498, in compress
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return comp.compress(data) + comp.flush()
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TypeError: 'str' does not support the buffer interface
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The above exception was the direct cause of the following exception:
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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TypeError: encoding with 'bz2' codec failed (TypeError: 'str' does not support the buffer interface)
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Finally, as the examples above show, these improvements have permitted
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the restoration of the convenience aliases for the non-Unicode codecs that
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were themselves restored in Python 3.2. This means that encoding binary data
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to and from its hexadecimal representation (for example) can now be written
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as::
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>>> from codecs import encode, decode
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>>> encode(b"hello", "hex")
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b'68656c6c6f'
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>>> decode(b"68656c6c6f", "hex")
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b'hello'
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The binary and text transforms provided in the standard library are detailed
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in :ref:`binary-transforms` and :ref:`text-transforms`.
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(Contributed by Nick Coghlan in :issue:`7475`, :issue:`17827`,
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:issue:`17828` and :issue:`19619`)
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.. _whatsnew-pep-451:
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PEP 451: A ModuleSpec Type for the Import System
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------------------------------------------------
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:pep:`451` provides an encapsulation of the information about a module that the
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import machinery will use to load it (that is, a module specification). This
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helps simplify both the import implementation and several import-related APIs.
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The change is also a stepping stone for `several future import-related
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improvements`__.
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__ https://mail.python.org/pipermail/python-dev/2013-November/130111.html
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The public-facing changes from the PEP are entirely backward-compatible.
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Furthermore, they should be transparent to everyone but importer authors. Key
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finder and loader methods have been deprecated, but they will continue working.
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New importers should use the new methods described in the PEP. Existing
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importers should be updated to implement the new methods. See the
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:ref:`deprecated-3.4` section for a list of methods that should be replaced and
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their replacements.
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Other Language Changes
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----------------------
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Some smaller changes made to the core Python language are:
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* Unicode database updated to UCD version 6.3.
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* :func:`min` and :func:`max` now accept a *default* keyword-only argument that
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can be used to specify the value they return if the iterable they are
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evaluating has no elements. (Contributed by Julian Berman in
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:issue:`18111`.)
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* Module objects are now :mod:`weakref`'able.
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* Module ``__file__`` attributes (and related values) should now always
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contain absolute paths by default, with the sole exception of
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``__main__.__file__`` when a script has been executed directly using
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a relative path (Contributed by Brett Cannon in :issue:`18416`).
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* All the UTF-\* codecs (except UTF-7) now reject surrogates during both
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encoding and decoding unless the ``surrogatepass`` error handler is used,
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with the exception of the UTF-16 decoder (which accepts valid surrogate pairs)
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and the UTF-16 encoder (which produces them while encoding non-BMP characters).
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Contributed by Victor Stinner, Kang-Hao (Kenny) Lu and Serhiy Storchaka in
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:issue:`12892`.
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* New German EBCDIC :ref:`codec <standard-encodings>` ``cp273``. (Contributed
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by Michael Bierenfeld and Andrew Kuchling in :issue:`1097797`.)
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* New Ukrainian :ref:`codec <standard-encodings>` ``cp1125``. (Contributed by
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Serhiy Storchaka in :issue:`19668`.)
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* :class:`bytes`.join() and :class:`bytearray`.join() now accept arbitrary
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buffer objects as arguments. (Contributed by Antoine Pitrou in
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:issue:`15958`.)
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* The :class:`int` constructor now accepts any object that has an ``__index__``
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method for its *base* argument. (Contributed by Mark Dickinson in
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:issue:`16772`.)
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* Frame objects now have a :func:`~frame.clear` method that clears all
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references to local variables from the frame. (Contributed by Antoine Pitrou
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in :issue:`17934`.)
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* :class:`memoryview` is now registered as a :class:`Sequence <collections.abc>`,
|
|
and supports the :func:`reversed` builtin. (Contributed by Nick Coghlan
|
|
and Claudiu Popa in :issue:`18690` and :issue:`19078`.)
|
|
|
|
* Signatures reported by :func:`help` have been modified and improved in
|
|
several cases as a result of the introduction of Argument Clinic and other
|
|
changes to the :mod:`inspect` and :mod:`pydoc` modules.
|
|
|
|
* :meth:`~object.__length_hint__` is now part of the formal language
|
|
specification (see :pep:`424`). (Contributed by Armin Ronacher in
|
|
:issue:`16148`.)
|
|
|
|
|
|
New Modules
|
|
===========
|
|
|
|
|
|
.. _whatsnew-asyncio:
|
|
|
|
asyncio
|
|
-------
|
|
|
|
The new :mod:`asyncio` module (defined in :pep:`3156`) provides a standard
|
|
pluggable event loop model for Python, providing solid asynchronous IO
|
|
support in the standard library, and making it easier for other event loop
|
|
implementations to interoperate with the standard library and each other.
|
|
|
|
For Python 3.4, this module is considered a :term:`provisional API`.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`3156` -- Asynchronous IO Support Rebooted: the "asyncio" Module
|
|
PEP written and implementation led by Guido van Rossum.
|
|
|
|
|
|
.. _whatsnew-ensurepip:
|
|
|
|
ensurepip
|
|
---------
|
|
|
|
The new :mod:`ensurepip` module is the primary infrastructure for the
|
|
:pep:`453` implementation. In the normal course of events end users will not
|
|
need to interact with this module, but it can be used to manually bootstrap
|
|
``pip`` if the automated bootstrapping into an installation or virtual
|
|
environment was declined.
|
|
|
|
:mod:`ensurepip` includes a bundled copy of ``pip``, up-to-date as of the first
|
|
release candidate of the release of CPython with which it ships (this applies
|
|
to both maintenance releases and feature releases). ``ensurepip`` does not
|
|
access the internet. If the installation has Internet access, after
|
|
``ensurepip`` is run the bundled ``pip`` can be used to upgrade ``pip`` to a
|
|
more recent release than the bundled one. (Note that such an upgraded version
|
|
of ``pip`` is considered to be a separately installed package and will not be
|
|
removed if Python is uninstalled.)
|
|
|
|
The module is named *ensure*\ pip because if called when ``pip`` is already
|
|
installed, it does nothing. It also has an ``--upgrade`` option that will
|
|
cause it to install the bundled copy of ``pip`` if the existing installed
|
|
version of ``pip`` is older than the bundled copy.
|
|
|
|
|
|
.. _whatsnew-enum:
|
|
|
|
enum
|
|
----
|
|
|
|
The new :mod:`enum` module (defined in :pep:`435`) provides a standard
|
|
implementation of enumeration types, allowing other modules (such as
|
|
:mod:`socket`) to provide more informative error messages and better
|
|
debugging support by replacing opaque integer constants with backwards
|
|
compatible enumeration values.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`435` -- Adding an Enum type to the Python standard library
|
|
PEP written by Barry Warsaw, Eli Bendersky and Ethan Furman,
|
|
implemented by Ethan Furman.
|
|
|
|
|
|
.. _whatsnew-pathlib:
|
|
|
|
pathlib
|
|
-------
|
|
|
|
The new :mod:`pathlib` module offers classes representing filesystem paths
|
|
with semantics appropriate for different operating systems. Path classes are
|
|
divided between *pure paths*, which provide purely computational operations
|
|
without I/O, and *concrete paths*, which inherit from pure paths but also
|
|
provide I/O operations.
|
|
|
|
For Python 3.4, this module is considered a :term:`provisional API`.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`428` -- The pathlib module -- object-oriented filesystem paths
|
|
PEP written and implemented by Antoine Pitrou.
|
|
|
|
|
|
.. _whatsnew-selectors:
|
|
|
|
selectors
|
|
---------
|
|
|
|
The new :mod:`selectors` module (created as part of implementing :pep:`3156`)
|
|
allows high-level and efficient I/O multiplexing, built upon the
|
|
:mod:`select` module primitives.
|
|
|
|
|
|
.. _whatsnew-statistics:
|
|
|
|
statistics
|
|
----------
|
|
|
|
The new :mod:`statistics` module (defined in :pep:`450`) offers some core
|
|
statistics functionality directly in the standard library. This module
|
|
supports calculation of the mean, median, mode, variance and standard
|
|
deviation of a data series.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`450` -- Adding A Statistics Module To The Standard Library
|
|
PEP written and implemented by Steven D'Aprano
|
|
|
|
.. _whatsnew-tracemalloc:
|
|
|
|
|
|
tracemalloc
|
|
-----------
|
|
|
|
The new :mod:`tracemalloc` module (defined in :pep:`454`) is a debug tool to
|
|
trace memory blocks allocated by Python. It provides the following information:
|
|
|
|
* Trace where an object was allocated
|
|
* Statistics on allocated memory blocks per filename and per line number:
|
|
total size, number and average size of allocated memory blocks
|
|
* Compute the differences between two snapshots to detect memory leaks
|
|
|
|
.. seealso::
|
|
|
|
:pep:`454` -- Add a new tracemalloc module to trace Python memory allocations
|
|
PEP written and implemented by Victor Stinner
|
|
|
|
|
|
|
|
Improved Modules
|
|
================
|
|
|
|
|
|
abc
|
|
---
|
|
|
|
New function :func:`abc.get_cache_token` can be used to know when to invalidate
|
|
caches that are affected by changes in the object graph. (Contributed
|
|
by Łukasz Langa in :issue:`16832`.)
|
|
|
|
New class :class:`~abc.ABC` has :class:`~abc.ABCMeta` as its meta class.
|
|
Using ``ABC`` as a base class has essentially the same effect as specifying
|
|
``metaclass=abc.ABCMeta``, but is simpler to type and easier to read.
|
|
(Contributed by Bruno Dupuis in :issue:`16049`.)
|
|
|
|
|
|
aifc
|
|
----
|
|
|
|
The :meth:`~aifc.aifc.getparams` method now returns a namedtuple rather than a
|
|
plain tuple. (Contributed by Claudiu Popa in :issue:`17818`.)
|
|
|
|
:func:`aifc.open` now supports the context manager protocol: when used in a
|
|
:keyword:`with` block, the :meth:`~aifc.aifc.close` method of the returned
|
|
object will be called automatically at the end of the block. (Contributed by
|
|
Serhiy Storchacha in :issue:`16486`.)
|
|
|
|
The :meth:`~aifc.aifc.writeframesraw` and :meth:`~aifc.aifc.writeframes`
|
|
methods now accept any :term:`bytes-like object`. (Contributed by Serhiy
|
|
Storchaka in :issue:`8311`.)
|
|
|
|
|
|
argparse
|
|
--------
|
|
|
|
The :class:`~argparse.FileType` class now accepts *encoding* and
|
|
*errors* arguments, which are passed through to :func:`open`. (Contributed
|
|
by Lucas Maystre in :issue:`11175`.)
|
|
|
|
|
|
audioop
|
|
-------
|
|
|
|
:mod:`audioop` now supports 24-bit samples. (Contributed by Serhiy Storchaka
|
|
in :issue:`12866`.)
|
|
|
|
New :func:`~audioop.byteswap` function converts big-endian samples to
|
|
little-endian and vice versa (Contributed by Serhiy Storchaka in
|
|
:issue:`19641`).
|
|
|
|
All :mod:`audioop` functions now accept any :term:`bytes-like object`. Strings
|
|
are not accepted: they didn't work before, now they raise an error right away.
|
|
(Contributed by Serhiy Storchaka in :issue:`16685`.)
|
|
|
|
|
|
base64
|
|
------
|
|
|
|
The encoding and decoding functions in :mod:`base64` now accept any
|
|
:term:`bytes-like object` in cases where it previously required a
|
|
:class:`bytes` or :class:`bytearray` instance. (Contributed by Nick Coghlan in
|
|
:issue:`17839`.)
|
|
|
|
New functions :func:`~base64.a85encode`, :func:`~base64.a85decode`,
|
|
:func:`~base64.b85encode`, and :func:`~base64.b85decode` provide the ability to
|
|
encode and decode binary data from and to ``Ascii85`` and the git/mercurial
|
|
``Base85`` formats, respectively. The ``a85`` functions have options that can
|
|
be used to make them compatible with the variants of the ``Ascii85`` encoding,
|
|
including the Adobe variant. (Contributed by Martin Morrison, the Mercurial
|
|
project, Serhiy Storchaka, and Antoine Pitrou in :issue:`17618`.)
|
|
|
|
|
|
collections
|
|
-----------
|
|
|
|
The :meth:`.ChainMap.new_child` method now accepts an *m* argument specifying
|
|
the child map to add to the chain. This allows an existing mapping and/or a
|
|
custom mapping type to be used for the child. (Contributed by Vinay Sajip in
|
|
:issue:`16613`.)
|
|
|
|
|
|
colorsys
|
|
--------
|
|
|
|
The number of digits in the coefficients for the RGB --- YIQ conversions have
|
|
been expanded so that they match the FCC NTSC versions. The change in
|
|
results should be less than 1% and may better match results found elsewhere.
|
|
(Contributed by Brian Landers and Serhiy Storchaka in :issue:`14323`.)
|
|
|
|
|
|
contextlib
|
|
----------
|
|
|
|
The new :class:`contextlib.suppress` context manager helps to clarify the
|
|
intent of code that deliberately suppresses exceptions from a single
|
|
statement. (Contributed by Raymond Hettinger in :issue:`15806` and
|
|
Zero Piraeus in :issue:`19266`)
|
|
|
|
The new :func:`contextlib.redirect_stdout` context manager makes it easier
|
|
for utility scripts to handle inflexible APIs that write their output to
|
|
:data:`sys.stdout` and don't provide any options to redirect it. Using the
|
|
context manager, the :data:`sys.stdout` output can be redirected to any
|
|
other stream or, in conjunction with :class:`io.StringIO`, to a string.
|
|
The latter can be especially useful, for example, to capture output
|
|
from a function that was written to implement a command line interface.
|
|
It is recommended only for utility scripts because it affects the
|
|
global state of :data:`sys.stdout`. (Contributed by Raymond Hettinger
|
|
in :issue:`15805`)
|
|
|
|
The :mod:`contextlib` documentation has also been updated to include a
|
|
:ref:`discussion <single-use-reusable-and-reentrant-cms>` of the
|
|
differences between single use, reusable and reentrant context managers.
|
|
|
|
|
|
dbm
|
|
---
|
|
|
|
:func:`dbm.open` objects now support the context management protocol. When
|
|
used in a :keyword:`with` statement, the ``close`` method of the database
|
|
object will be called automatically at the end of the block. (Contributed by
|
|
Claudiu Popa and Nick Coghlan in :issue:`19282`.)
|
|
|
|
|
|
dis
|
|
---
|
|
|
|
Functions :func:`~dis.show_code`, :func:`~dis.dis`, :func:`~dis.distb`, and
|
|
:func:`~dis.disassemble` now accept a keyword-only *file* argument that
|
|
controls where they write their output.
|
|
|
|
The :mod:`dis` module is now built around an :class:`~dis.Instruction` class
|
|
that provides object oriented access to the details of each individual bytecode
|
|
operation.
|
|
|
|
A new method, :func:`~dis.get_instructions`, provides an iterator that emits
|
|
the Instruction stream for a given piece of Python code. Thus it is now
|
|
possible to write a program that inspects and manipulates a bytecode
|
|
object in ways different from those provided by the :mod:`~dis` module
|
|
itself. For example::
|
|
|
|
>>> import dis
|
|
>>> for instr in dis.get_instructions(lambda x: x + 1):
|
|
... print(instr.opname)
|
|
LOAD_FAST
|
|
LOAD_CONST
|
|
BINARY_ADD
|
|
RETURN_VALUE
|
|
|
|
The various display tools in the :mod:`dis` module have been rewritten to use
|
|
these new components.
|
|
|
|
In addition, a new application-friendly class :class:`~dis.Bytecode` provides
|
|
an object-oriented API for inspecting bytecode in both in human-readable form
|
|
and for iterating over instructions. The :class:`~dis.Bytecode` constructor
|
|
takes the same arguments that :func:`~dis.get_instruction` does (plus an
|
|
optional *current_offset*), and the resulting object can be iterated to produce
|
|
:class:`~dis.Instruction` objects. But it also has a :mod:`~dis.Bytecode.dis`
|
|
method, equivalent to calling :mod:`~dis.dis` on the constructor argument, but
|
|
returned as a multi-line string::
|
|
|
|
>>> bytecode = dis.Bytecode(lambda x: x +1, current_offset=3)
|
|
>>> for instr in bytecode:
|
|
... print('{} ({})'.format(instr.opname, instr.opcode))
|
|
LOAD_FAST (124)
|
|
LOAD_CONST (100)
|
|
BINARY_ADD (23)
|
|
RETURN_VALUE (83)
|
|
>>> bytecode.dis().splitlines() # doctest: +NORMALIZE_WHITESPACE
|
|
[' 1 0 LOAD_FAST 0 (x)',
|
|
' --> 3 LOAD_CONST 1 (1)',
|
|
' 6 BINARY_ADD',
|
|
' 7 RETURN_VALUE']
|
|
|
|
:class:`~dis.Bytecode` also has a class method,
|
|
:meth:`~dis.Bytecode.from_traceback`, that provides the ability to manipulate a
|
|
traceback (that is, ``print(Bytecode.from_traceback(tb).dis())`` is equivalent
|
|
to ``distb(tb)``).
|
|
|
|
(Contributed by Nick Coghlan, Ryan Kelly and Thomas Kluyver in :issue:`11816`
|
|
and Claudiu Popa in :issue:`17916`)
|
|
|
|
New function :func:`~dis.stack_effect` computes the effect on the Python stack
|
|
of a given opcode and argument, information that is not otherwise available.
|
|
(Contributed by Larry Hastings in :issue:`19722`.)
|
|
|
|
|
|
doctest
|
|
-------
|
|
|
|
A new :ref:`option flag <doctest-options>`, :data:`~doctest.FAIL_FAST`, halts
|
|
test running as soon as the first failure is detected. (Contributed by R.
|
|
David Murray and Daniel Urban in :issue:`16522`.)
|
|
|
|
The :mod:`doctest` command line interface now uses :mod:`argparse`, and has two
|
|
new options, ``-o`` and ``-f``. ``-o`` allows :ref:`doctest options
|
|
<doctest-options>` to be specified on the command line, and ``-f`` is a
|
|
shorthand for ``-o FAIL_FAST`` (to parallel the similar option supported by the
|
|
:mod:`unittest` CLI). (Contributed by R. David Murray in :issue:`11390`.)
|
|
|
|
:mod:`doctest` will now find doctests in extension module ``__doc__`` strings.
|
|
(Contributed by Zachary Ware in :issue:`3158`.)
|
|
|
|
|
|
email
|
|
-----
|
|
|
|
:meth:`~email.message.Message.as_string` now accepts a *policy* argument to
|
|
override the default policy of the message when generating a string
|
|
representation of it. This means that ``as_string`` can now be used in more
|
|
circumstances, instead of having to create and use a :mod:`~email.generator` in
|
|
order to pass formatting parameters to its ``flatten`` method. (Contributed by
|
|
R. David Murray in :issue:`18600`.)
|
|
|
|
New method :meth:`~email.message.Message.as_bytes` added to produce a bytes
|
|
representation of the message in a fashion similar to how ``as_string``
|
|
produces a string representation. It does not accept the *maxheaderlen*
|
|
argument, but does accept the *unixfrom* and *policy* arguments. The
|
|
:class:`~email.message.Message` :meth:`~email.message.Message.__bytes__` method
|
|
calls it, meaning that ``bytes(mymsg)`` will now produce the intuitive
|
|
result: a bytes object containing the fully formatted message. (Contributed
|
|
by R. David Murray in :issue:`18600`.)
|
|
|
|
The :meth:`.Message.set_param` message now accepts a *replace* keyword argument.
|
|
When specified, the associated header will be updated without changing
|
|
its location in the list of headers. For backward compatibility, the default
|
|
is ``False``. (Contributed by R. David Murray in :issue:`18891`.)
|
|
|
|
|
|
.. _whatsnew_email_contentmanager:
|
|
|
|
A pair of new subclasses of :class:`~email.message.Message` have been added
|
|
(:class:`.EmailMessage` and :class:`.MIMEPart`), along with a new sub-module,
|
|
:mod:`~email.contentmanager` and a new :mod:`~email.policy` attribute
|
|
:attr:`~email.policy.EmailPolicy.content_manager`. All documentation is
|
|
currently in the new module, which is being added as part of email's new
|
|
:term:`provisional API`. These classes provide a number of new methods that
|
|
make extracting content from and inserting content into email messages much
|
|
easier. For details, see the :mod:`~email.contentmanager` documentation and
|
|
the :ref:`email-contentmanager-api-examples`. These API additions complete the
|
|
bulk of the work that was planned as part of the email6 project. The currently
|
|
provisional API is scheduled to become final in Python 3.5 (possibly with a few
|
|
minor additions in the area of error handling). (Contributed by R. David
|
|
Murray in :issue:`18891`.)
|
|
|
|
|
|
filecmp
|
|
-------
|
|
|
|
A new :func:`~filecmp.clear_cache` function provides the ability to clear the
|
|
:mod:`filecmp` comparison cache, which uses :func:`os.stat` information to
|
|
determine if the file has changed since the last compare. This can be used,
|
|
for example, if the file might have been changed and re-checked in less time
|
|
than the resolution of a particular filesystem's file modification time field.
|
|
(Contributed by Mark Levitt in :issue:`18149`.)
|
|
|
|
New module attribute :data:`~filecmp.DEFAULT_IGNORES` provides the list of
|
|
directories that are used as the default value for the *ignore* parameter of
|
|
the :func:`~filecmp.dircmp` function. (Contributed by Eli Bendersky in
|
|
:issue:`15442`.)
|
|
|
|
|
|
functools
|
|
---------
|
|
|
|
The new :func:`~functools.partialmethod` descriptor brings partial argument
|
|
application to descriptors, just as :func:`~functools.partial` provides
|
|
for normal callables. The new descriptor also makes it easier to get
|
|
arbitrary callables (including :func:`~functools.partial` instances)
|
|
to behave like normal instance methods when included in a class definition.
|
|
(Contributed by Alon Horev and Nick Coghlan in :issue:`4331`)
|
|
|
|
.. _whatsnew-singledispatch:
|
|
|
|
The new :func:`~functools.singledispatch` decorator brings support for
|
|
single-dispatch generic functions to the Python standard library. Where
|
|
object oriented programming focuses on grouping multiple operations on a
|
|
common set of data into a class, a generic function focuses on grouping
|
|
multiple implementations of an operation that allows it to work with
|
|
*different* kinds of data.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`443` -- Single-dispatch generic functions
|
|
PEP written and implemented by Łukasz Langa.
|
|
|
|
:func:`~functools.total_ordering` now supports a return value of
|
|
:const:`NotImplemented` from the underlying comparison function. (Contributed
|
|
by Katie Miller in :issue:`10042`.)
|
|
|
|
A pure-python version of the :func:`~functools.partial` function is now in the
|
|
stdlib; in CPython it is overridden by the C accelerated version, but it is
|
|
available for other implementations to use. (Contributed by Brian Thorne in
|
|
:issue:`12428`.)
|
|
|
|
|
|
gc
|
|
--
|
|
|
|
New function :func:`~gc.get_stats` returns a list of three per-generation
|
|
dictionaries containing the collections statistics since interpreter startup.
|
|
(Contributed by Antoine Pitrou in :issue:`16351`.)
|
|
|
|
|
|
glob
|
|
----
|
|
|
|
A new function :func:`~glob.escape` provides a way to escape special characters
|
|
in a filename so that they do not become part of the globbing expansion but are
|
|
instead matched literally. (Contributed by Serhiy Storchaka in :issue:`8402`.)
|
|
|
|
|
|
hashlib
|
|
-------
|
|
|
|
A new :func:`hashlib.pbkdf2_hmac` function provides
|
|
the `PKCS#5 password-based key derivation function 2
|
|
<http://en.wikipedia.org/wiki/PBKDF2>`_. (Contributed by Christian
|
|
Heimes in :issue:`18582`)
|
|
|
|
The :attr:`~hashlib.hash.name` attribute of :mod:`hashlib` hash objects is now
|
|
a formally supported interface. It has always existed in CPython's
|
|
:mod:`hashlib` (although it did not return lower case names for all supported
|
|
hashes), but it was not a public interface and so some other Python
|
|
implementations have not previously supported it. (Contributed by Jason R.
|
|
Coombs in :issue:`18532`.)
|
|
|
|
|
|
hmac
|
|
----
|
|
|
|
:mod:`hmac` now accepts ``bytearray`` as well as ``bytes`` for the *key*
|
|
argument to the :func:`~hmac.new` function, and the *msg* parameter to both the
|
|
:func:`~hmac.new` function and the :meth:`~hmac.HMAC.update` method now
|
|
accepts any type supported by the :mod:`hashlib` module. (Contributed
|
|
by Jonas Borgström in :issue:`18240`.)
|
|
|
|
The *digestmod* argument to the :func:`hmac.new` function may now be any hash
|
|
digest name recognized by :mod:`hashlib`. In addition, the current behavior in
|
|
which the value of *digestmod* defaults to ``MD5`` is deprecated: in a
|
|
future version of Python there will be no default value. (Contributed by
|
|
Christian Heimes in :issue:`17276`.)
|
|
|
|
With the addition of :attr:`~hmac.HMAC.block_size` and :attr:`~hmac.HMAC.name`
|
|
attributes (and the formal documentation of the :attr:`~hmac.HMAC.digest_size`
|
|
attribute), the :mod:`hmac` module now conforms fully to the :pep:`247` API.
|
|
(Contributed by Christian Heimes in :issue:`18775`.)
|
|
|
|
|
|
html
|
|
----
|
|
|
|
New function :func:`~html.unescape` function converts HTML5 character references to
|
|
the corresponding Unicode characters. (Contributed by Ezio Melotti in
|
|
:issue:`2927`)
|
|
|
|
:class:`~html.parser.HTMLParser` accepts a new keyword argument
|
|
*convert_charrefs* that, when ``True``, automatically converts all character
|
|
references. For backward-compatibility, its value defaults to ``False``, but
|
|
it will change to ``True`` in a future version of Python, so you are invited to
|
|
set it explicitly and update your code to use this new feature. (Contributed
|
|
by Ezio Melotti in :issue:`13633`)
|
|
|
|
The *strict* argument of :class:`~html.parser.HTMLParser` is now deprecated.
|
|
(Contributed by Ezio Melotti in :issue:`15114`)
|
|
|
|
|
|
http
|
|
----
|
|
|
|
:meth:`~http.server.BaseHTTPRequestHandler.send_error` now accepts an
|
|
optional additional *explain* parameter which can be used to provide an
|
|
extended error description, overriding the hardcoded default if there is one.
|
|
This extended error description will be formatted using the
|
|
:attr:`~http.server.HTTP.error_message_format` attribute and sent as the body
|
|
of the error response. (Contributed by Karl Cow in :issue:`12921`.)
|
|
|
|
The :mod:`http.server` :ref:`command line interface <http-server-cli>` now has
|
|
a ``-b/--bind`` option that causes the server to listen on a specific address.
|
|
(Contributed by Malte Swart in :issue:`17764`.)
|
|
|
|
|
|
importlib
|
|
---------
|
|
|
|
The :class:`~importlib.abc.InspectLoader` ABC defines a new method,
|
|
:meth:`~importlib.abc.InspectLoader.source_to_code` that accepts source
|
|
data and a path and returns a code object. The default implementation
|
|
is equivalent to ``compile(data, path, 'exec', dont_inherit=True)``.
|
|
(Contributed by Eric Snow and Brett Cannon in :issue:`15627`.)
|
|
|
|
:class:`~importlib.abc.InspectLoader` also now has a default implementation
|
|
for the :meth:`~importlib.abc.InspectLoader.get_code` method. However,
|
|
it will normally be desirable to override the default implementation
|
|
for performance reasons. (Contributed by Brett Cannon in :issue:`18072`.)
|
|
|
|
The :func:`~importlib.reload` function has been moved from :mod:`imp` to
|
|
:mod:`importlib` as part of the :mod:`imp` module deprecation. (Contributed by
|
|
Berker Peksag in :issue:`18193`.)
|
|
|
|
:mod:`importlib.util` now has a :data:`~importlib.util.MAGIC_NUMBER` attribute
|
|
providing access to the bytecode version number. This replaces the
|
|
:func:`~imp.get_magic` function in the deprecated :mod:`imp` module.
|
|
(Contributed by Brett Cannon in :issue:`18192`.)
|
|
|
|
New :mod:`importlib.util` functions :func:`~importlib.util.cache_from_source`
|
|
and :func:`~importlib.util.source_from_cache` replace the same-named functions
|
|
in the deprecated :mod:`imp` module. (Contributed by Brett Cannon in
|
|
:issue:`18194`.)
|
|
|
|
The :mod:`importlib` bootstrap :class:`.NamespaceLoader` now conforms to
|
|
the :class:`.InspectLoader` ABC, which means that ``runpy`` and
|
|
``python -m`` can now be used with namespace packages. (Contributed
|
|
by Brett Cannon in :issue:`18058`.)
|
|
|
|
:mod:`importlib.util` has a new function :func:`~importlib.util.decode_source`
|
|
that decodes source from bytes using universal newline processing. This is
|
|
useful for implementing :meth:`.InspectLoader.get_source` methods.
|
|
|
|
:class:`importlib.machinery.ExtensionFileLoader` now has a
|
|
:meth:`~importlib.machinery.ExtensionFileLoader.get_filename` method. This was
|
|
inadvertently omitted in the original implementation. (Contributed by Eric
|
|
Snow in :issue:`19152`.)
|
|
|
|
|
|
inspect
|
|
-------
|
|
|
|
The :mod:`inspect` module now offers a basic :ref:`command line interface
|
|
<inspect-module-cli>` to quickly display source code and other
|
|
information for modules, classes and functions. (Contributed by Claudiu Popa
|
|
and Nick Coghlan in :issue:`18626`)
|
|
|
|
:func:`~inspect.unwrap` makes it easy to unravel wrapper function chains
|
|
created by :func:`functools.wraps` (and any other API that sets the
|
|
``__wrapped__`` attribute on a wrapper function). (Contributed by
|
|
Daniel Urban, Aaron Iles and Nick Coghlan in :issue:`13266`)
|
|
|
|
As part of the implementation of the new :mod:`enum` module, the
|
|
:mod:`inspect` module now has substantially better support for custom
|
|
``__dir__`` methods and dynamic class attributes provided through
|
|
metaclasses (Contributed by Ethan Furman in :issue:`18929` and
|
|
:issue:`19030`)
|
|
|
|
:func:`~inspect.getfullargspec` and :func:`~inspect.getargspec`
|
|
now use the :func:`~inspect.signature` API. This allows them to
|
|
support a much broader range of callables, including those with
|
|
``__signature__`` attributes, those with metadata provided by argument
|
|
clinic, :func:`functools.partial` objects and more. Note that, unlike
|
|
:func:`~inspect.signature`, these functions still ignore ``__wrapped__``
|
|
attributes, and report the already bound first argument for bound methods,
|
|
so it is still necessary to update your code to use
|
|
:func:`~inspect.signature` directly if those features are desired.
|
|
(Contributed by Yury Selivanov in :issue:`17481`)
|
|
|
|
:func:`~inspect.signature` now supports duck types of CPython functions,
|
|
which adds support for functions compiled with Cython. (Contributed
|
|
by Stefan Behnel and Yury Selivanov in :issue:`17159`)
|
|
|
|
|
|
ipaddress
|
|
---------
|
|
|
|
:mod:`ipaddress` was added to the standard library in Python 3.3 as a
|
|
:term:`provisional API`. With the release of Python 3.4, this qualification
|
|
has been removed: :mod:`ipaddress` is now considered a stable API, covered
|
|
by the normal standard library requirements to maintain backwards
|
|
compatibility.
|
|
|
|
A new :attr:`~ipaddress.IPv4Address.is_global` property is ``True`` if
|
|
an address is globally routeable. (Contributed by Peter Moody in
|
|
:issue:`17400`.)
|
|
|
|
|
|
logging
|
|
-------
|
|
|
|
The :class:`~logging.handlers.TimedRotatingFileHandler` has a new *atTime*
|
|
parameter that can be used to specify the time of day when rollover should
|
|
happen. (Contributed by Ronald Oussoren in :issue:`9556`.)
|
|
|
|
:class:`~logging.handlers.SocketHandler` and
|
|
:class:`~logging.handlers.DatagramHandler` now support Unix domain sockets (by
|
|
setting *port* to ``None``). (Contributed by Vinay Sajip in commit
|
|
ce46195b56a9.)
|
|
|
|
:func:`~logging.config.fileConfig` now accepts a
|
|
:class:`configparser.RawConfigParser` subclass instance for the *fname*
|
|
parameter. This facilitates using a configuration file when logging
|
|
configuration is just a part of the overall application configuration, or where
|
|
the application modifies the configuration before passing it to
|
|
:func:`~logging.config.fileConfig`. (Contributed by Vinay Sajip in
|
|
:issue:`16110`.)
|
|
|
|
Logging configuration data received from a socket via the
|
|
:func:`logging.config.listen` function can now be validated before being
|
|
processed by supplying a verification function as the argument to the new
|
|
*verify* keyword argument. (Contributed by Vinay Sajip in :issue:`15452`.)
|
|
|
|
|
|
.. _whatsnew-marshal-3:
|
|
|
|
marshal
|
|
-------
|
|
|
|
The default :mod:`marshal` version has been bumped to 3. The code implementing
|
|
the new version restores the Python2 behavior of recording only one copy of
|
|
interned strings and preserving the interning on deserialization, and extends
|
|
this "one copy" ability to any object type (including handling recursive
|
|
references). This reduces both the size of ``.pyc`` files and the amount of
|
|
memory a module occupies in memory when it is loaded from a ``.pyc`` (or
|
|
``.pyo``) file. (Contributed by Kristján Valur Jónsson in :issue:`16475`,
|
|
with additional speedups by Antoine Pitrou in :issue:`19219`.)
|
|
|
|
|
|
mmap
|
|
----
|
|
|
|
mmap objects can now be :mod:`weakref`\ ed. (Contributed by Valerie Lambert in
|
|
:issue:`4885`.)
|
|
|
|
|
|
multiprocessing
|
|
---------------
|
|
|
|
.. _whatsnew-multiprocessing-no-fork:
|
|
|
|
On Unix two new :ref:`start methods <multiprocessing-start-methods>`,
|
|
(``spawn`` and ``forkserver``, have been added for starting processes using
|
|
:mod:`multiprocessing`. These make the mixing of processes with threads more
|
|
robust, and the ``spawn`` method matches the semantics that multiprocessing has
|
|
always used on Windows. New function
|
|
:func:`~multiprocessing.get_all_start_methods` reports all start methods
|
|
available on the platform, :func:`~multiprocessing.get_start_method` reports
|
|
the current start method, and :func:`~multiprocessing.set_start_method` sets
|
|
the start method. (Contributed by Richard Oudkerk in :issue:`8713`).
|
|
|
|
:mod:`multiprocessing` also now has the concept of a ``context``, which
|
|
determines how child processes are created. New function
|
|
:func:`~multiprocessing.get_context` returns a context that uses a specified
|
|
start method. It has the same API as the :mod:`multiprocessing` module itself,
|
|
so you can use it to create :class:`~multiprocessing.pool.Pool`\ s and other
|
|
objects that will operate within that context. This allows a framework and an
|
|
application or different parts of the same application to use multiprocessing
|
|
without interfering with each other. (Contributed by Richard Oudkerk in
|
|
:issue:`18999`.)
|
|
|
|
Except when using the old *fork* start method, child processes no longer
|
|
inherit unneeded handles/file descriptors from their parents (part of
|
|
:issue:`8713`).
|
|
|
|
:mod:`multiprocessing` now relies on :mod:`runpy` (which implements the
|
|
``-m`` switch) to initialise ``__main__`` appropriately in child processes
|
|
when using the ``spawn`` or ``forkserver`` start methods. This resolves some
|
|
edge cases where combining multiprocessing, the ``-m`` command line switch,
|
|
and explicit relative imports could cause obscure failures in child
|
|
processes. (Contributed by Nick Coghlan in :issue:`19946`)
|
|
|
|
|
|
operator
|
|
--------
|
|
|
|
New function :func:`~operator.length_hint` provides an implementation of the
|
|
specification for how the :meth:`~object.__length_hint__` special method should
|
|
be used, as part of the :pep:`424` formal specification of this language
|
|
feature. (Contributed by Armin Ronacher in :issue:`16148`.)
|
|
|
|
There is now a pure-python version of the :mod:`operator` module available for
|
|
reference and for use by alternate implementations of Python. (Contributed by
|
|
Zachary Ware in :issue:`16694`.)
|
|
|
|
|
|
os
|
|
--
|
|
|
|
There are new functions to get and set the :ref:`inheritable flag
|
|
<fd_inheritance>` of a file descriptor (:func:`os.get_inheritable`,
|
|
:func:`os.set_inheritable`) or a Windows handle
|
|
(:func:`os.get_handle_inheritable`, :func:`os.set_handle_inheritable`).
|
|
|
|
New function :func:`~os.cpu_count` reports the number of CPUs available on the
|
|
platform on which Python is running (or ``None`` if the count can't be
|
|
determined). The :func:`multiprocessing.cpu_count` function is now implemented
|
|
in terms of this function). (Contributed by Trent Nelson, Yogesh Chaudhari,
|
|
Victor Stinner, and Charles-François Natali in :issue:`17914`.)
|
|
|
|
:func:`os.path.samestat` is now available on the Windows platform (and the
|
|
:func:`os.path.samefile` implementation is now shared between Unix and
|
|
Windows). (Contributed by Brian Curtin in :issue:`11939`.)
|
|
|
|
:func:`os.path.ismount` now recognizes volumes mounted below a drive
|
|
root on Windows. (Contributed by Tim Golden in :issue:`9035`.)
|
|
|
|
:func:`os.open` supports two new flags on platforms that provide them,
|
|
:data:`~os.O_PATH` (un-opened file descriptor), and :data:`~os.O_TMPFILE`
|
|
(unnamed temporary file; as of 3.4.0 release available only on Linux systems
|
|
with a kernel version of 3.11 or newer that have uapi headers). (Contributed
|
|
by Christian Heimes in :issue:`18673` and Benjamin Peterson, respectively.)
|
|
|
|
|
|
pdb
|
|
---
|
|
|
|
:mod:`pdb` has been enhanced to handle generators, :keyword:`yield`, and
|
|
``yield from`` in a more useful fashion. This is especially helpful when
|
|
debugging :mod:`asyncio` based programs. (Contributed by Andrew Svetlov and
|
|
Xavier de Gaye in :issue:`16596`.)
|
|
|
|
The ``print`` command has been removed from :mod:`pdb`, restoring access to the
|
|
Python :func:`print` function from the pdb command line. Python2's ``pdb`` did
|
|
not have a ``print`` command; instead, entering ``print`` executed the
|
|
``print`` statement. In Python3 ``print`` was mistakenly made an alias for the
|
|
pdb :pdbcmd:`p` command. ``p``, however, prints the ``repr`` of its argument,
|
|
not the ``str`` like the Python2 ``print`` command did. Worse, the Python3
|
|
``pdb print`` command shadowed the Python3 ``print`` function, making it
|
|
inaccessible at the ``pdb`` prompt. (Contributed by Connor Osborn in
|
|
:issue:`18764`.)
|
|
|
|
|
|
.. _whatsnew-protocol-4:
|
|
|
|
pickle
|
|
------
|
|
|
|
:mod:`pickle` now supports (but does not use by default) a new pickle protocol,
|
|
protocol 4. This new protocol addresses a number of issues that were present
|
|
in previous protocols, such as the serialization of nested classes, very large
|
|
strings and containers, and classes whose :meth:`__new__` method takes
|
|
keyword-only arguments. It also provides some efficiency improvements.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`3154` -- Pickle protocol 4
|
|
PEP written by Antoine Pitrou and implemented by Alexandre Vassalotti.
|
|
|
|
|
|
plistlib
|
|
--------
|
|
|
|
:mod:`plistlib` now has an API that is similar to the standard pattern for
|
|
stdlib serialization protocols, with new :func:`~plistlib.load`,
|
|
:func:`~plistlib.dump`, :func:`~plistlib.loads`, and :func:`~plistlib.dumps`
|
|
functions. (The older API is now deprecated.) In addition to the already
|
|
supported XML plist format (:data:`~plistlib.FMT_XML`), it also now supports
|
|
the binary plist format (:data:`~plistlib.FMT_BINARY`). (Contributed by Ronald
|
|
Oussoren and others in :issue:`14455`).
|
|
|
|
|
|
poplib
|
|
------
|
|
|
|
Two new methods have been added to :mod:`poplib`: :meth:`~poplib.POP3.capa`,
|
|
which returns the list of capabilities advertised by the POP server, and
|
|
:meth:`~poplib.POP3.stls`, which switches a clear-text POP3 session into an
|
|
encrypted POP3 session if the POP server supports it. (Contributed by Lorenzo
|
|
Catucci in :issue:`4473`.)
|
|
|
|
|
|
pprint
|
|
------
|
|
|
|
The :mod:`pprint` module's :class:`~pprint.PrettyPrinter` class and its
|
|
:func:`~pprint.pformat`, and :func:`~pprint.pprint` functions have a new
|
|
option, *compact*, that controls how the output is formatted. Currently
|
|
setting *compact* to ``True`` means that sequences will be printed with as many
|
|
sequence elements as will fit within *width* on each (indented) line.
|
|
(Contributed by Serhiy Storchaka in :issue:`19132`.)
|
|
|
|
Long strings are now wrapped using Python's normal line continuation
|
|
syntax. (Contributed by Antoine Pitrou in :issue:`17150`).
|
|
|
|
|
|
pty
|
|
---
|
|
|
|
:func:`pty.spawn` now returns the status value from :func:`os.waitpid` on
|
|
the child process, instead of ``None``. (Contributed by Gregory P. Smith.)
|
|
|
|
|
|
pydoc
|
|
-----
|
|
|
|
The :mod:`pydoc` module is now based directly on the :func:`inspect.signature`
|
|
introspection API, allowing it to provide signature information for a wider
|
|
variety of callable objects. This change also means that ``__wrapped__``
|
|
attributes are now taken into account when displaying help information
|
|
(Contributed by Larry Hastings in :issue:`19674`)
|
|
|
|
The :mod:`pydoc` module no longer displays the ``self`` parameter for
|
|
already bound methods. Instead, it aims to always display the exact current
|
|
signature of the supplied callable (Contributed by Larry Hastings in
|
|
:issue:`20710`)
|
|
|
|
In addition to the changes that have been made to :mod:`pydoc` directly,
|
|
its handling of custom ``__dir__`` methods and various descriptor
|
|
behaviours has also been improved substantially by the underlying changes in
|
|
the :mod:`inspect` module.
|
|
|
|
As the :func:`help` builtin is based on :mod:`pydoc`, the above changes also
|
|
affect the behaviour of :func:`help`.
|
|
|
|
|
|
re
|
|
--
|
|
|
|
New :func:`~re.fullmatch` function and :meth:`.regex.fullmatch` method anchor
|
|
the pattern at both ends of the string to match. This provides a way to be
|
|
explicit about the goal of the match, which avoids a class of subtle bugs where
|
|
``$`` characters get lost during code changes or the addition of alternatives
|
|
to an existing regular expression. (Contributed by Matthew Barnett in
|
|
:issue:`16203`.)
|
|
|
|
The repr of :ref:`regex objects <re-objects>` now includes the pattern
|
|
and the flags; the repr of :ref:`match objects <match-objects>` now
|
|
includes the start, end, and the part of the string that matched. (Contributed
|
|
by Hugo Lopes Tavares and Serhiy Storchaka in :issue:`13592` and
|
|
:issue:`17087`.)
|
|
|
|
|
|
resource
|
|
--------
|
|
|
|
New :func:`~resource.prlimit` function, available on Linux platforms with a
|
|
kernel version of 2.6.36 or later and glibc of 2.13 or later, provides the
|
|
ability to query or set the resource limits for processes other than the one
|
|
making the call. (Contributed by Christian Heimes in :issue:`16595`.)
|
|
|
|
On Linux kernel version 2.6.36 or later, there are there are also some new
|
|
Linux specific constants: :attr:`~resource.RLIMIT_MSGQUEUE`,
|
|
:attr:`~resource.RLIMIT_NICE`, :attr:`~resource.RLIMIT_RTPRIO`,
|
|
:attr:`~resource.RLIMIT_RTTIME`, and :attr:`~resource.RLIMIT_SIGPENDING`.
|
|
(Contributed by Christian Heimes in :issue:`19324`.)
|
|
|
|
On FreeBSD version 9 and later, there some new FreeBSD specific constants:
|
|
:attr:`~resource.RLIMIT_SBSIZE`, :attr:`~resource.RLIMIT_SWAP`, and
|
|
:attr:`~resource.RLIMIT_NPTS`. (Contributed by Claudiu Popa in
|
|
:issue:`19343`.)
|
|
|
|
|
|
select
|
|
------
|
|
|
|
:class:`~select.epoll` objects now support the context management protocol.
|
|
When used in a :keyword:`with` statement, the :meth:`~select.epoll.close`
|
|
method will be called automatically at the end of the block. (Contributed
|
|
by Serhiy Storchaka in :issue:`16488`.)
|
|
|
|
:class:`~select.devpoll` objects now have :meth:`~select.devpoll.fileno` and
|
|
:meth:`~select.devpoll.close` methods, as well as a new attribute
|
|
:attr:`~select.devpoll.closed`. (Contributed by Victor Stinner in
|
|
:issue:`18794`.)
|
|
|
|
|
|
shelve
|
|
------
|
|
|
|
:class:`~shelve.Shelf` instances may now be used in :keyword:`with` statements,
|
|
and will be automatically closed at the end of the :keyword:`with` block.
|
|
(Contributed by Filip Gruszczyński in :issue:`13896`.)
|
|
|
|
|
|
shutil
|
|
------
|
|
|
|
:func:`~shutil.copyfile` now raises a specific :exc:`~shutil.Error` subclass,
|
|
:exc:`~shutil.SameFileError`, when the source and destination are the same
|
|
file, which allows an application to take appropriate action on this specific
|
|
error. (Contributed by Atsuo Ishimoto and Hynek Schlawack in
|
|
:issue:`1492704`.)
|
|
|
|
|
|
smtpd
|
|
-----
|
|
|
|
The :class:`~smtpd.SMTPServer` and :class:`~smtpd.SMTPChannel` classes now
|
|
accept a *map* keyword argument which, if specified, is passed in to
|
|
:class:`asynchat.async_chat` as its *map* argument. This allows an application
|
|
to avoid affecting the global socket map. (Contributed by Vinay Sajip in
|
|
:issue:`11959`.)
|
|
|
|
|
|
smtplib
|
|
-------
|
|
|
|
:exc:`~smtplib.SMTPException` is now a subclass of :exc:`OSError`, which allows
|
|
both socket level errors and SMTP protocol level errors to be caught in one
|
|
try/except statement by code that only cares whether or not an error occurred.
|
|
(Contributed by Ned Jackson Lovely in :issue:`2118`).
|
|
|
|
|
|
socket
|
|
------
|
|
|
|
The socket module now supports the :data:`~socket.CAN_BCM` protocol on
|
|
platforms that support it. (Contributed by Brian Thorne in :issue:`15359`.)
|
|
|
|
Socket objects have new methods to get or set their :ref:`inheritable flag
|
|
<fd_inheritance>`, :meth:`~socket.socket.get_inheritable` and
|
|
:meth:`~socket.socket.set_inheritable`.
|
|
|
|
The ``socket.AF_*`` and ``socket.SOCK_*`` constants are now enumeration values
|
|
using the new :mod:`enum` module. This allows meaningful names to be printed
|
|
during debugging, instead of integer "magic numbers".
|
|
|
|
The :data:`~socket.AF_LINK` constant is now available on BSD and OSX.
|
|
|
|
:func:`~socket.inet_pton` and :func:`~socket.inet_ntop` are now supported
|
|
on Windows. (Contributed by Atsuo Ishimoto in :issue:`7171`.)
|
|
|
|
|
|
sqlite3
|
|
-------
|
|
|
|
A new boolean parameter to the :func:`~sqlite3.connect` function, *uri*, can be
|
|
used to indicate that the *database* parameter is a ``uri`` (see the `SQLite
|
|
URI documentation <http://www.sqlite.org/uri.html>`_). (Contributed by poq in
|
|
:issue:`13773`.)
|
|
|
|
|
|
ssl
|
|
---
|
|
|
|
.. _whatsnew-tls-11-12:
|
|
|
|
:data:`~ssl.PROTOCOL_TLSv1_1` and :data:`~ssl.PROTOCOL_TLSv1_2` (TLSv1.1 and
|
|
TLSv1.2 support) have been added; support for these protocols is only available if
|
|
Python is linked with OpenSSL 1.0.1 or later. (Contributed by Michele Orrù and
|
|
Antoine Pitrou in :issue:`16692`)
|
|
|
|
.. _whatsnew34-sslcontext:
|
|
|
|
New function :func:`~ssl.create_default_context` provides a standard way to
|
|
obtain an :class:`~ssl.SSLContext` whose settings are intended to be a
|
|
reasonable balance between compatibility and security. These settings are
|
|
more stringent than the defaults provided by the :class:`~ssl.SSLContext`
|
|
constructor, and may be adjusted in the future, without prior deprecation, if
|
|
best-practice security requirements change. The new recommended best
|
|
practice for using stdlib libraries that support SSL is to use
|
|
:func:`~ssl.create_default_context` to obtain an :class:`~ssl.SSLContext`
|
|
object, modify it if needed, and then pass it as the *context* argument
|
|
of the appropriate stdlib API. (Contributed by Christian Heimes
|
|
in :issue:`19689`.)
|
|
|
|
:class:`~ssl.SSLContext` method :meth:`~ssl.SSLContext.load_verify_locations`
|
|
accepts a new optional argument *cadata*, which can be used to provide PEM or
|
|
DER encoded certificates directly via strings or bytes, respectively.
|
|
(Contributed by Christian Heimes in :issue:`18138`.)
|
|
|
|
New function :func:`~ssl.get_default_verify_paths` returns
|
|
a named tuple of the paths and environment variables that the
|
|
:meth:`~ssl.SSLContext.set_default_verify_paths` method uses to set
|
|
OpenSSL's default ``cafile`` and ``capath``. This can be an aid in
|
|
debugging default verification issues. (Contributed by Christian Heimes
|
|
in :issue:`18143`.)
|
|
|
|
:class:`~ssl.SSLContext` has a new method,
|
|
:meth:`~ssl.SSLContext.cert_store_stats`, that reports the number of loaded
|
|
``X.509`` certs, ``X.509 CA`` certs, and certificate revocation lists (``crl``\
|
|
s), as well as a :meth:`~ssl.SSLContext.get_ca_certs` method that returns a
|
|
list of the loaded ``CA`` certificates. (Contributed by Christian Heimes in
|
|
:issue:`18147`.)
|
|
|
|
If OpenSSL 0.9.8 or later is available, :class:`~ssl.SSLContext` has an new
|
|
attribute :attr:`~ssl.SSLContext.verify_flags` that can be used to control the
|
|
certificate verification process by setting it to some combination of the new
|
|
constants :data:`~ssl.VERIFY_DEFAULT`, :data:`~ssl.VERIFY_CRL_CHECK_LEAF`,
|
|
:data:`~ssl.VERIFY_CRL_CHECK_CHAIN`, or :data:`~ssl.VERIFY_X509_STRICT`.
|
|
OpenSSL does not do any CRL verification by default. (Contributed by
|
|
Christien Heimes in :issue:`8813`.)
|
|
|
|
New :class:`~ssl.SSLContext` method :meth:`~ssl.SSLContext.load_default_certs`
|
|
loads a set of default "certificate authority" (CA) certificates from default
|
|
locations, which vary according to the platform. It can be used to load both
|
|
TLS web server authentication certificates
|
|
(``purpose=``:data:`~ssl.Purpose.SERVER_AUTH`) for a client to use to verify a
|
|
server, and certificates for a server to use in verifying client certificates
|
|
(``purpose=``:data:`~ssl.Purpose.CLIENT_AUTH`). (Contributed by Christian
|
|
Heimes in :issue:`19292`.)
|
|
|
|
.. _whatsnew34-win-cert-store:
|
|
|
|
Two new windows-only functions, :func:`~ssl.enum_certificates` and
|
|
:func:`~ssl.enum_crls` provide the ability to retrieve certificates,
|
|
certificate information, and CRLs from the Windows cert store. (Contributed
|
|
by Christian Heimes in :issue:`17134`.)
|
|
|
|
.. _whatsnew34-sni:
|
|
|
|
Support for server-side SNI (Server Name Indication) using the new
|
|
:meth:`ssl.SSLContext.set_servername_callback` method.
|
|
(Contributed by Daniel Black in :issue:`8109`.)
|
|
|
|
The dictionary returned by :meth:`.SSLSocket.getpeercert` contains additional
|
|
``X509v3`` extension items: ``crlDistributionPoints``, ``calIssuers``, and
|
|
``OCSP`` URIs. (Contributed by Christian Heimes in :issue:`18379`.)
|
|
|
|
|
|
stat
|
|
----
|
|
|
|
The :mod:`stat` module is now backed by a C implementation in :mod:`_stat`. A C
|
|
implementation is required as most of the values aren't standardized and
|
|
are platform-dependent. (Contributed by Christian Heimes in :issue:`11016`.)
|
|
|
|
The module supports new :mod:`~stat.ST_MODE` flags, :mod:`~stat.S_IFDOOR`,
|
|
:attr:`~stat.S_IFPORT`, and :attr:`~stat.S_IFWHT`. (Contributed by
|
|
Christian Hiemes in :issue:`11016`.)
|
|
|
|
|
|
struct
|
|
------
|
|
|
|
New function :mod:`~struct.iter_unpack` and a new
|
|
:meth:`struct.Struct.iter_unpack` method on compiled formats provide streamed
|
|
unpacking of a buffer containing repeated instances of a given format of data.
|
|
(Contributed by Antoine Pitrou in :issue:`17804`.)
|
|
|
|
|
|
subprocess
|
|
----------
|
|
|
|
:func:`~subprocess.check_output` now accepts an *input* argument that can
|
|
be used to provide the contents of ``stdin`` for the command that is run.
|
|
(Contributed by Zack Weinberg in :issue:`16624`.)
|
|
|
|
:func:`~subprocess.getstatus` and :func:`~subprocess.getstatusoutput` now
|
|
work on Windows. This change was actually inadvertently made in 3.3.4.
|
|
(Contributed by Tim Golden in :issue:`10197`.)
|
|
|
|
|
|
sunau
|
|
-----
|
|
|
|
The :meth:`~sunau.getparams` method now returns a namedtuple rather than a
|
|
plain tuple. (Contributed by Claudiu Popa in :issue:`18901`.)
|
|
|
|
:meth:`sunau.open` now supports the context manager protocol: when used in a
|
|
:keyword:`with` block, the ``close`` method of the returned object will be
|
|
called automatically at the end of the block. (Contributed by Serhiy Storchaka
|
|
in :issue:`18878`.)
|
|
|
|
:meth:`.AU_write.setsampwidth` now supports 24 bit samples, thus adding
|
|
support for writing 24 sample using the module. (Contributed by
|
|
Serhiy Storchaka in :issue:`19261`.)
|
|
|
|
The :meth:`~sunau.AU_write.writeframesraw` and
|
|
:meth:`~sunau.AU_write.writeframes` methods now accept any :term:`bytes-like
|
|
object`. (Contributed by Serhiy Storchaka in :issue:`8311`.)
|
|
|
|
|
|
sys
|
|
---
|
|
|
|
New function :func:`sys.getallocatedblocks` returns the current number of
|
|
blocks allocated by the interpreter. (In CPython with the default
|
|
``--with-pymalloc`` setting, this is allocations made through the
|
|
:c:func:`PyObject_Malloc` API.) This can be useful for tracking memory leaks,
|
|
especially if automated via a test suite. (Contributed by Antoine Pitrou
|
|
in :issue:`13390`.)
|
|
|
|
When the Python interpreter starts in :ref:`interactive mode
|
|
<tut-interactive>`, it checks for an :data:`~sys.__interactivehook__` attribute
|
|
on the :mod:`sys` module. If the attribute exists, its value is called with no
|
|
arguments just before interactive mode is started. The check is made after the
|
|
:envvar:`PYTHONSTARTUP` file is read, so it can be set there. The :mod:`site`
|
|
module :ref:`sets it <rlcompleter-config>` to a function that enables tab
|
|
completion and history saving (in :file:`~/.python-history`) if the platform
|
|
supports :mod:`readline`. If you do not want this (new) behavior, you can
|
|
override it in :envvar:`PYTHONSTARTUP`, :mod:`sitecustomize`, or
|
|
:mod:`usercustomize` by deleting this attribute from :mod:`sys` (or setting it
|
|
to some other callable). (Contributed by Éric Araujo and Antoine Pitrou in
|
|
:issue:`5845`.)
|
|
|
|
|
|
tarfile
|
|
-------
|
|
|
|
The :mod:`tarfile` module now supports a simple :ref:`tarfile-commandline` when
|
|
called as a script directly or via ``-m``. This can be used to create and
|
|
extract tarfile archives. (Contributed by Berker Peksag in :issue:`13477`.)
|
|
|
|
|
|
textwrap
|
|
--------
|
|
|
|
The :class:`~textwrap.TextWrapper` class has two new attributes/constructor
|
|
arguments: :attr:`~textwrap.TextWrapper.max_lines`, which limits the number of
|
|
lines in the output, and :attr:`~textwrap.TextWrapper.placeholder`, which is a
|
|
string that will appear at the end of the output if it has been truncated
|
|
because of *max_lines*. Building on these capabilities, a new convenience
|
|
function :func:`~textwrap.shorten` collapses all of the whitespace in the input
|
|
to single spaces and produces a single line of a given *width* that ends with
|
|
the *placeholder* (by default, ``[...]``). (Contributed by Antoine Pitrou and
|
|
Serhiy Storchaka in :issue:`18585` and :issue:`18725`.)
|
|
|
|
|
|
threading
|
|
---------
|
|
|
|
The :class:`~threading.Thread` object representing the main thread can be
|
|
obtained from the new :func:`~threading.main_thread` function. In normal
|
|
conditions this will be the thread from which the Python interpreter was
|
|
started. (Contributed by Andrew Svetlov in :issue:`18882`.)
|
|
|
|
|
|
traceback
|
|
---------
|
|
|
|
A new :func:`traceback.clear_frames` function takes a traceback object
|
|
and clears the local variables in all of the frames it references,
|
|
reducing the amount of memory consumed. (Contributed by Andrew Kuchling in
|
|
:issue:`1565525`).
|
|
|
|
|
|
types
|
|
-----
|
|
|
|
A new :func:`~types.DynamicClassAttribute` descriptor provides a way to define
|
|
an attribute that acts normally when looked up through an instance object, but
|
|
which is routed to the *class* ``__getattr__`` when looked up through the
|
|
class. This allows one to have properties active on a class, and have virtual
|
|
attributes on the class with the same name (see :mod:`Enum` for an example).
|
|
(Contributed by Ethan Furman in :issue:`19030`.)
|
|
|
|
|
|
urllib
|
|
------
|
|
|
|
:mod:`urllib.request` now supports ``data:`` URLs via the
|
|
:class:`~urllib.request.DataHandler` class. (Contributed by Mathias Panzenböck
|
|
in :issue:`16423`.)
|
|
|
|
The http method that will be used by a :class:`~urllib.request.Request` class
|
|
can now be specified by setting a :class:`~urllib.request.Request.method`
|
|
class attribute on the subclass. (Contributed by Jason R Coombs in
|
|
:issue:`18978`.)
|
|
|
|
:class:`~urllib.request.Request` objects are now reusable: if the
|
|
:attr:`~urllib.request.Request.full_url` or :attr:`~urllib.request.Request.data`
|
|
attributes are modified, all relevant internal properties are updated. This
|
|
means, for example, that it is now possible to use the same
|
|
:class:`~urllib.request.Request` object in more than one
|
|
:meth:`.OpenerDirector.open` call with different *data* arguments, or to
|
|
modify a :class:`~urllib.request.Request`\ 's ``url`` rather than recomputing it
|
|
from scratch. There is also a new
|
|
:meth:`~urllib.request.Request.remove_header` method that can be used to remove
|
|
headers from a :class:`~urllib.request.Request`. (Contributed by Alexey
|
|
Kachayev in :issue:`16464`, Daniel Wozniak in :issue:`17485`, and Damien Brecht
|
|
and Senthil Kumaran in :issue:`17272`.)
|
|
|
|
:class:`~urllib.error.HTTPError` objects now have a
|
|
:attr:`~urllib.error.HTTPError.headers` attribute that provides access to the
|
|
HTTP response headers associated with the error. (Contributed by
|
|
Berker Peksag in :issue:`15701`.)
|
|
|
|
|
|
unittest
|
|
--------
|
|
|
|
The :class:`~unittest.TestCase` class has a new method,
|
|
:meth:`~unittest.TestCase.subTest`, that produces a context manager whose
|
|
:keyword:`with` block becomes a "sub-test". This context manager allows a test
|
|
method to dynamically generate subtests by, say, calling the ``subTest``
|
|
context manager inside a loop. A single test method can thereby produce an
|
|
indefinite number of separately-identified and separately-counted tests, all of
|
|
which will run even if one or more of them fail. For example::
|
|
|
|
class NumbersTest(unittest.TestCase):
|
|
def test_even(self):
|
|
for i in range(6):
|
|
with self.subTest(i=i):
|
|
self.assertEqual(i % 2, 0)
|
|
|
|
will result in six subtests, each identified in the unittest verbose output
|
|
with a label consisting of the variable name ``i`` and a particular value for
|
|
that variable (``i=0``, ``i=1``, etc). See :ref:`subtests` for the full
|
|
version of this example. (Contributed by Antoine Pitrou in :issue:`16997`.)
|
|
|
|
:func:`unittest.main` now accepts an iterable of test names for
|
|
*defaultTest*, where previously it only accepted a single test name as a
|
|
string. (Contributed by Jyrki Pulliainen in :issue:`15132`.)
|
|
|
|
If :class:`~unittest.SkipTest` is raised during test discovery (that is, at the
|
|
module level in the test file), it is now reported as a skip instead of an
|
|
error. (Contributed by Zach Ware in :issue:`16935`.)
|
|
|
|
:meth:`~unittest.TestLoader.discover` now sorts the discovered files to provide
|
|
consistent test ordering. (Contributed by Martin Melin and Jeff Ramnani in
|
|
:issue:`16709`.)
|
|
|
|
:class:`~unittest.TestSuite` now drops references to tests as soon as the test
|
|
has been run, if the test is successful. On Python interpreters that do
|
|
garbage collection, this allows the tests to be garbage collected if nothing
|
|
else is holding a reference to the test. It is possible to override this
|
|
behavior by creating a :class:`~unittest.TestSuite` subclass that defines a
|
|
custom ``_removeTestAtIndex`` method. (Contributed by Tom Wardill, Matt
|
|
McClure, and Andrew Svetlov in :issue:`11798`.)
|
|
|
|
A new test assertion context-manager, :meth:`~unittest.TestCase.assertLogs`,
|
|
will ensure that a given block of code emits a log message using the
|
|
:mod:`logging` module. By default the message can come from any logger and
|
|
have a priority of ``INFO`` or higher, but both the logger name and an
|
|
alternative minimum logging level may be specified. The object returned by the
|
|
context manager can be queried for the :class:`~logging.LogRecord`\ s and/or
|
|
formatted messages that were logged. (Contributed by Antoine Pitrou in
|
|
:issue:`18937`.)
|
|
|
|
Test discovery now works with namespace packages (Contributed by Claudiu Popa
|
|
in :issue:`17457`.)
|
|
|
|
:mod:`unittest.mock` objects now inspect their specification signatures when
|
|
matching calls, which means an argument can now be matched by either position
|
|
or name, instead of only by position. (Contributed by Antoine Pitrou in
|
|
:issue:`17015`.)
|
|
|
|
:func:`~mock.mock_open` objects now have ``readline`` and ``readlines``
|
|
methods. (Contributed by Toshio Kuratomi in :issue:`17467`.)
|
|
|
|
|
|
venv
|
|
----
|
|
|
|
:mod:`venv` now includes activation scripts for the ``csh`` and ``fish``
|
|
shells (Contributed by Andrew Svetlov in :issue:`15417`.)
|
|
|
|
:class:`~venv.EnvBuilder` and the :func:`~venv.create` convenience function
|
|
take a new keyword argument *with_pip*, which defaults to ``False``, that
|
|
controls whether or not :class:`~venv.EnvBuilder` ensures that ``pip`` is
|
|
installed in the virtual environment. (Contributed by Nick Coghlan in
|
|
:issue:`19552` as part of the :pep:`453` implementation.)
|
|
|
|
|
|
wave
|
|
----
|
|
|
|
The :meth:`~wave.getparams` method now returns a namedtuple rather than a
|
|
plain tuple. (Contributed by Claudiu Popa in :issue:`17487`.)
|
|
|
|
:meth:`wave.open` now supports the context manager protocol. (Contributed
|
|
by Claudiu Popa in :issue:`17616`.)
|
|
|
|
:mod:`wave` can now :ref:`write output to unseekable files
|
|
<wave-write-objects>`. (Contributed by David Jones, Guilherme Polo, and Serhiy
|
|
Storchaka in :issue:`5202`.)
|
|
|
|
The :meth:`~wave.Wave_write.writeframesraw` and
|
|
:meth:`~wave.Wave_write.writeframes` methods now accept any :term:`bytes-like
|
|
object`. (Contributed by Serhiy Storchaka in :issue:`8311`.)
|
|
|
|
|
|
weakref
|
|
-------
|
|
|
|
New :class:`~weakref.WeakMethod` class simulates weak references to bound
|
|
methods. (Contributed by Antoine Pitrou in :issue:`14631`.)
|
|
|
|
New :class:`~weakref.finalize` class makes it possible to register a callback
|
|
to be invoked when an object is garbage collected, without needing to
|
|
carefully manage the lifecycle of the weak reference itself. (Contributed by
|
|
Richard Oudkerk in :issue:`15528`)
|
|
|
|
The callback, if any, associated with a :class:`~weakref.ref` is now
|
|
exposed via the :attr:`~weakref.ref.__callback__` attribute. (Contributed
|
|
by Mark Dickinson in :issue:`17643`.)
|
|
|
|
|
|
xml.etree
|
|
---------
|
|
|
|
A new parser, :class:`~xml.etree.ElementTree.XMLPullParser`, allows a
|
|
non-blocking applications to parse XML documents. An example can be
|
|
seen at :ref:`elementtree-pull-parsing`. (Contributed by Antoine
|
|
Pitrou in :issue:`17741`.)
|
|
|
|
The :mod:`xml.etree.ElementTree` :func:`~xml.etree.ElementTree.tostring` and
|
|
:func:`~xml.etree.ElementTree.tostringlist` functions, and the
|
|
:class:`~xml.etree.ElementTree.ElementTree`
|
|
:meth:`~xml.etree.ElementTree.ElementTree.write` method, now have a
|
|
*short_empty_elements* :ref:`keyword-only parameter <keyword-only_parameter>`
|
|
providing control over whether elements with no content are written in
|
|
abbreviated (``<tag />``) or expanded (``<tag></tag>``) form. (Contributed by
|
|
Ariel Poliak and Serhiy Storchaka in :issue:`14377`.)
|
|
|
|
|
|
zipfile
|
|
-------
|
|
|
|
The :meth:`~zipfile.PyZipFile.writepy` method of the
|
|
:class:`~zipfile.PyZipFile` class has a new *filterfunc* option that can be
|
|
used to control which directories and files are added to the archive. For
|
|
example, this could be used to exclude test files from the archive.
|
|
(Contributed by Christian Tismer in :issue:`19274`.)
|
|
|
|
The *allowZip64* parameter to :class:`~zipfile.ZipFile` and
|
|
:class:`~zipfile.PyZipfile` is now ``True`` by default. (Contributed by
|
|
William Mallard in :issue:`17201`.)
|
|
|
|
|
|
|
|
CPython Implementation Changes
|
|
==============================
|
|
|
|
|
|
.. _whatsnew-pep-445:
|
|
|
|
PEP 445: Customization of CPython Memory Allocators
|
|
---------------------------------------------------
|
|
|
|
:pep:`445` adds new C level interfaces to customize memory allocation in
|
|
the CPython interpreter.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`445` -- Add new APIs to customize Python memory allocators
|
|
PEP written and implemented by Victor Stinner.
|
|
|
|
|
|
.. _whatsnew-pep-442:
|
|
|
|
PEP 442: Safe Object Finalization
|
|
---------------------------------
|
|
|
|
:pep:`442` removes the current limitations and quirks of object finalization
|
|
in CPython. With it, objects with :meth:`__del__` methods, as well as
|
|
generators with :keyword:`finally` clauses, can be finalized when they are
|
|
part of a reference cycle.
|
|
|
|
As part of this change, module globals are no longer forcibly set to
|
|
:const:`None` during interpreter shutdown in most cases, instead relying
|
|
on the normal operation of the cyclic garbage collector. This avoids a
|
|
whole class of interpreter-shutdown-time errors, usually involving
|
|
``__del__`` methods, that have plagued Python since the cyclic GC
|
|
was first introduced.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`442` -- Safe object finalization
|
|
PEP written and implemented by Antoine Pitrou.
|
|
|
|
|
|
.. _whatsnew-pep-456:
|
|
|
|
PEP 456: Secure and Interchangeable Hash Algorithm
|
|
--------------------------------------------------
|
|
|
|
:pep:`456` follows up on earlier security fix work done on Python's hash
|
|
algorithm to address certain DOS attacks to which public facing APIs backed by
|
|
dictionary lookups may be subject. (See :issue:`14621` for the start of the
|
|
current round of improvements.) The PEP unifies CPython's hash code to make it
|
|
easier for a packager to substitute a different hash algorithm, and switches
|
|
Python's default implementation to a SipHash implementation on platforms that
|
|
have a 64 bit data type. Any performance differences in comparison with the
|
|
older FNV algorithm are trivial.
|
|
|
|
The PEP adds additional fields to the :attr:`sys.hash_info` struct sequence to
|
|
describe the hash algorithm in use by the currently executing binary. Otherwise,
|
|
the PEP does not alter any existing CPython APIs.
|
|
|
|
|
|
.. _whatsnew-pep-436:
|
|
|
|
PEP 436: Argument Clinic
|
|
------------------------
|
|
|
|
"Argument Clinic" (:pep:`436`) is now part of the CPython build process
|
|
and can be used to simplify the process of defining and maintaining
|
|
accurate signatures for builtins and standard library extension modules
|
|
implemented in C.
|
|
|
|
Some standard library extension modules have been converted to use Argument
|
|
Clinic in Python 3.4, and :mod:`pydoc` and :mod:`inspect` have been updated
|
|
accordingly.
|
|
|
|
It is expected that signature metadata for programmatic introspection will
|
|
be added to additional callables implemented in C as part of Python 3.4
|
|
maintenance releases.
|
|
|
|
.. note::
|
|
The Argument Clinic PEP is not fully up to date with the state of the
|
|
implementation. This has been deemed acceptable by the release manager
|
|
and core development team in this case, as Argument Clinic will not
|
|
be made available as a public API for third party use in Python 3.4.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`436` -- The Argument Clinic DSL
|
|
PEP written and implemented by Larry Hastings.
|
|
|
|
|
|
Other Build and C API Changes
|
|
-----------------------------
|
|
|
|
* The new :c:func:`PyType_GetSlot` function has been added to the stable ABI,
|
|
allowing retrieval of function pointers from named type slots when using
|
|
the limited API. (Contributed by Martin von Löwis in :issue:`17162`)
|
|
|
|
* The new :c:func:`Py_SetStandardStreamEncoding` pre-initialization API
|
|
allows applications embedding the CPython interpreter to reliably force
|
|
a particular encoding and error handler for the standard streams
|
|
(Contributed by Bastien Montagne and Nick Coghlan in :issue:`16129`)
|
|
|
|
* Most Python C APIs that don't mutate string arguments are now correctly
|
|
marked as accepting ``const char *`` rather than ``char *`` (Contributed
|
|
by Serhiy Storchaka in :issue:`1772673`).
|
|
|
|
* A new shell version of ``python-config`` can be used even when a python
|
|
interpreter is not available (for example, in cross compilation scenarios).
|
|
|
|
* :c:func:`PyUnicode_FromFormat` now supports width and precision
|
|
specifications for ``%s``, ``%A``, ``%U``, ``%V``, ``%S``, and ``%R``.
|
|
(Contributed by Ysj Ray and Victor Stinner in :issue:`7330`.)
|
|
|
|
* New function :c:func:`PyStructSequence_InitType2` supplements the
|
|
existing :c:func:`PyStructSequence_InitType` function. The difference
|
|
is that it returns ``0`` on success and ``-1`` on failure.
|
|
|
|
* The CPython source can now be compiled using the address sanity checking
|
|
features of recent versions of GCC and clang: the false alarms in the small
|
|
object allocator have been silenced. (Contributed by Dhiru Kholia in
|
|
:issue:`18596`.)
|
|
|
|
* The Windows build now uses `Address Space Layout Randomization
|
|
<http://en.wikipedia.org/wiki/ASLR>`_ and `Data Execution Prevention
|
|
<http://en.wikipedia.org/wiki/Data_Execution_Prevention>`_. (Contributed by
|
|
Christian Heimes in :issue:`16632`.)
|
|
|
|
* New function :c:func:`PyObject_LengthHint` is the C API equivalent
|
|
of :func:`operator.length_hint`. (Contributed by Armin Ronacher in
|
|
:issue:`16148`.)
|
|
|
|
|
|
.. _other-improvements-3.4:
|
|
|
|
Other Improvements
|
|
------------------
|
|
|
|
.. _whatsnew-isolated-mode:
|
|
|
|
* The :ref:`python <using-on-cmdline>` command has a new :ref:`option
|
|
<using-on-misc-options>`, ``-I``, which causes it to run in "isolated mode",
|
|
which means that :data:`sys.path` contains neither the script's directory nor
|
|
the user's ``site-packages`` directory, and all :envvar:`PYTHON*` environment
|
|
variables are ignored (it implies both ``-s`` and ``-E``). Other
|
|
restrictions may also be applied in the future, with the goal being to
|
|
isolate the execution of a script from the user's environment. This is
|
|
appropriate, for example, when Python is used to run a system script. On
|
|
most POSIX systems it can and should be used in the ``#!`` line of system
|
|
scripts. (Contributed by Christian Heimes in :issue:`16499`.)
|
|
|
|
* Tab-completion is now enabled by default in the interactive interpreter
|
|
on systems that support :mod:`readline`. History is also enabled by default,
|
|
and is written to (and read from) the file :file:`~/.python-history`.
|
|
(Contributed by Antoine Pitrou and Éric Araujo in :issue:`5845`.)
|
|
|
|
* Invoking the Python interpreter with ``--version`` now outputs the version to
|
|
standard output instead of standard error (:issue:`18338`). Similar changes
|
|
were made to :mod:`argparse` (:issue:`18920`) and other modules that have
|
|
script-like invocation capabilities (:issue:`18922`).
|
|
|
|
* The CPython Windows installer now adds ``.py`` to the :envvar:`PATHEXT`
|
|
variable when extensions are registered, allowing users to run a python
|
|
script at the windows command prompt by just typing its name without the
|
|
``.py`` extension. (Contributed by Paul Moore in :issue:`18569`.)
|
|
|
|
* A new ``make`` target `coverage-report
|
|
<http://docs.python.org/devguide/coverage.html#measuring-coverage-of-c-code-with-gcov-and-lcov>`_
|
|
will build python, run the test suite, and generate an HTML coverage report
|
|
for the C codebase using ``gcov`` and `lcov
|
|
<http://ltp.sourceforge.net/coverage/lcov.php>`_.
|
|
|
|
* The ``-R`` option to the :ref:`python regression test suite <regrtest>` now
|
|
also checks for memory allocation leaks, using
|
|
:func:`sys.getallocatedblocks()`. (Contributed by Antoine Pitrou in
|
|
:issue:`13390`).
|
|
|
|
* ``python -m`` now works with namespace packages.
|
|
|
|
* The :mod:`stat` module is now implemented in C, which means it gets the
|
|
values for its constants from the C header files, instead of having the
|
|
values hard-coded in the python module as was previously the case.
|
|
|
|
* Loading multiple python modules from a single OS module (``.so``, ``.dll``)
|
|
now works correctly (previously it silently returned the first python
|
|
module in the file). (Contributed by Václav Šmilauer in :issue:`16421`.)
|
|
|
|
* A new opcode, :opcode:`LOAD_CLASSDEREF`, has been added to fix a bug in the
|
|
loading of free variables in class bodies that could be triggered by certain
|
|
uses of :ref:`__prepare__ <prepare>`. (Contributed by Benjamin Peterson in
|
|
:issue:`17853`.)
|
|
|
|
* A number of MemoryError-related crashes were identified and fixed by Victor
|
|
Stinner using his :pep:`445`-based ``pyfailmalloc`` tool (:issue:`18408`,
|
|
:issue:`18520`).
|
|
|
|
* The :ref:`pyvenv <scripts-pyvenv>` command now accepts a ``--copies`` option
|
|
to use copies rather than symlinks even on systems where symlinks are the
|
|
default. (Contributed by Vinay Sajip in :issue:`18807`.)
|
|
|
|
* The :ref:`pyvenv <scripts-pyvenv>` command also accepts a ``--without-pip``
|
|
option to suppress the otherwise-automatic bootstrapping of pip into
|
|
the virtual environment. (Contributed by Nick Coghlan in :issue:`19552`
|
|
as part of the :pep:`453` implementation.)
|
|
|
|
* The encoding name is now optional in the value set for the
|
|
:envvar:`PYTHONIOENCODING` environment variable. This makes it possible to
|
|
set just the error handler, without changing the default encoding.
|
|
(Contributed by Serhiy Storchaka in :issue:`18818`.)
|
|
|
|
* The :mod:`bz2`, :mod:`lzma`, and :mod:`gzip` module ``open`` functions now
|
|
support ``x`` (exclusive creation) mode. (Contributed by Tim Heaney and
|
|
Vajrasky Kok in :issue:`19201`, :issue:`19222`, and :issue:`19223`.)
|
|
|
|
|
|
Significant Optimizations
|
|
-------------------------
|
|
|
|
* The UTF-32 decoder is now 3x to 4x faster. (Contributed by Serhiy Storchaka
|
|
in :issue:`14625`.)
|
|
|
|
* The cost of hash collisions for sets is now reduced. Each hash table
|
|
probe now checks a series of consecutive, adjacent key/hash pairs before
|
|
continuing to make random probes through the hash table. This exploits
|
|
cache locality to make collision resolution less expensive.
|
|
The collision resolution scheme can be described as a hybrid of linear
|
|
probing and open addressing. The number of additional linear probes
|
|
defaults to nine. This can be changed at compile-time by defining
|
|
LINEAR_PROBES to be any value. Set LINEAR_PROBES=0 to turn-off
|
|
linear probing entirely. (Contributed by Raymond Hettinger in
|
|
:issue:`18771`.)
|
|
|
|
* The interpreter starts about 30% faster. A couple of measures lead to the
|
|
speedup. The interpreter loads fewer modules on startup, e.g. the :mod:`re`,
|
|
:mod:`collections` and :mod:`locale` modules and their dependencies are no
|
|
longer imported by default. The marshal module has been improved to load
|
|
compiled Python code faster. (Contributed by Antoine Pitrou, Christian
|
|
Heimes and Victor Stinner in :issue:`19219`, :issue:`19218`, :issue:`19209`,
|
|
:issue:`19205` and :issue:`9548`)
|
|
|
|
* :class:`bz2.BZ2File` is now as fast or faster than the Python2 version for
|
|
most cases. :class:`lzma.LZMAFile` has also been optimized. (Contributed by
|
|
Serhiy Storchaka and Nadeem Vawda in :issue:`16034`.)
|
|
|
|
* :func:`random.getrandbits` is 20%-40% faster for small integers (the most
|
|
common use case). (Contributed by Serhiy Storchaka in :issue:`16674`).
|
|
|
|
* By taking advantage of the new storage format for strings, pickling of
|
|
strings is now significantly faster. (Contributed by Victor Stinner and
|
|
Antoine Pitrou in :issue:`15596`.)
|
|
|
|
* A performance issue in :meth:`io.FileIO.readall` has been solved. This
|
|
particularly affects Windows, and significantly speeds up the case of piping
|
|
significant amounts of data through :mod:`subprocess`. (Contributed
|
|
by Richard Oudkerk in :issue:`15758`.)
|
|
|
|
* :func:`html.escape` is now 10x faster. (Contributed by Matt Bryant in
|
|
:issue:`18020`.)
|
|
|
|
* On Windows, the native ``VirtualAlloc`` is now used instead of the CRT
|
|
``malloc`` in ``obmalloc``. Artificial benchmarks show about a 3% memory
|
|
savings.
|
|
|
|
* :func:`os.urandom` now uses a lazily-opened persistent file descriptor
|
|
so as to avoid using many file descriptors when run in parallel from
|
|
multiple threads. (Contributed by Antoine Pitrou in :issue:`18756`.)
|
|
|
|
|
|
.. _deprecated-3.4:
|
|
|
|
Deprecated
|
|
==========
|
|
|
|
This section covers various APIs and other features that have been deprecated
|
|
in Python 3.4, and will be removed in Python 3.5 or later. In most (but not
|
|
all) cases, using the deprecated APIs will produce a :exc:`DeprecationWarning`
|
|
when the interpreter is run with deprecation warnings enabled (for example, by
|
|
using ``-Wd``).
|
|
|
|
|
|
Deprecations in the Python API
|
|
------------------------------
|
|
|
|
* As mentioned in :ref:`whatsnew-pep-451`, a number of :mod:`importilb`
|
|
methods and functions are deprecated: :meth:`importlib.find_loader` is
|
|
replaced by :func:`importlib.util.find_spec`;
|
|
:meth:`importlib.machinery.PathFinder.find_module` is replaced by
|
|
:meth:`importlib.machinery.PathFinder.find_spec`;
|
|
:meth:`importlib.abc.MetaPathFinder.find_module` is replaced by
|
|
:meth:`importlib.abc.MetaPathFinder.find_spec`;
|
|
:meth:`importlib.abc.PathEntryFinder.find_loader` and
|
|
:meth:`~importlib.abc.PathEntryFinder.find_module` are replaced by
|
|
:meth:`importlib.abc.PathEntryFinder.find_spec`; all of the ``xxxLoader`` ABC
|
|
``load_module`` methods (:meth:`importlib.abc.Loader.load_module`,
|
|
:meth:`importlib.abc.InspectLoader.load_module`,
|
|
:meth:`importlib.abc.FileLoader.load_module`,
|
|
:meth:`importlib.abc.SourceLoader.load_module`) should no longer be
|
|
implemented, instead loaders should implement an
|
|
``exec_module`` method
|
|
(:meth:`importlib.abc.Loader.exec_module`,
|
|
:meth:`importlib.abc.InspectLoader.exec_module`
|
|
:meth:`importlib.abc.SourceLoader.exec_module`) and let the import system
|
|
take care of the rest; and
|
|
:meth:`importlib.abc.Loader.module_repr`,
|
|
:meth:`importlib.util.module_for_loader`, :meth:`importlib.util.set_loader`,
|
|
and :meth:`importlib.util.set_package` are no longer needed because their
|
|
functions are now handled automatically by the import system.
|
|
|
|
* The :mod:`imp` module is pending deprecation. To keep compatibility with
|
|
Python 2/3 code bases, the module's removal is currently not scheduled.
|
|
|
|
* The :mod:`formatter` module is pending deprecation and is slated for removal
|
|
in Python 3.6.
|
|
|
|
* ``MD5`` as the default *digestmod* for the :func:`hmac.new` function is
|
|
deprecated. Python 3.6 will require an explicit digest name or constructor as
|
|
*digestmod* argument.
|
|
|
|
* The internal ``Netrc`` class in the :mod:`ftplib` module has been documented
|
|
as deprecated in its docstring for quite some time. It now emits a
|
|
:exc:`DeprecationWarning` and will be removed completely in Python 3.5.
|
|
|
|
* The undocumented *endtime* argument to :meth:`subprocess.Popen.wait` should
|
|
not have been exposed and is hopefully not in use; it is deprecated and
|
|
will mostly likely be removed in Python 3.5.
|
|
|
|
* The *strict* argument of :class:`~html.parser.HTMLParser` is deprecated.
|
|
|
|
* The :mod:`plistlib` :func:`~plistlib.readPlist`,
|
|
:func:`~plistlib.writePlist`, :func:`~plistlib.readPlistFromBytes`, and
|
|
:func:`~plistlib.writePlistToBytes` functions are deprecated in favor of the
|
|
corresponding new functions :func:`~plistlib.load`, :func:`~plistlib.dump`,
|
|
:func:`~plistlib.loads`, and :func:`~plistlib.dumps`. :func:`~plistlib.Data`
|
|
is deprecated in favor of just using the :class:`bytes` constructor.
|
|
|
|
* The :mod:`sysconfig` key ``SO`` is deprecated, it has been replaced by
|
|
``EXT_SUFFIX``.
|
|
|
|
* The ``U`` mode accepted by various ``open`` functions is deprecated.
|
|
In Python3 it does not do anything useful, and should be replaced by
|
|
appropriate uses of :class:`io.TextIOWrapper` (if needed) and its *newline*
|
|
argument.
|
|
|
|
* The *parser* argument of :func:`xml.etree.ElementTree.iterparse` has
|
|
been deprecated, as has the *html* argument of
|
|
:func:`~xml.etree.ElementTree.XMLParser`. To prepare for the removal of the
|
|
latter, all arguments to ``XMLParser`` should be passed by keyword.
|
|
|
|
|
|
Deprecated Features
|
|
-------------------
|
|
|
|
* Running :ref:`idle` with the ``-n`` flag (no subprocess) is deprecated.
|
|
However, the feature will not be removed until :issue:`18823` is resolved.
|
|
|
|
* The site module adding a "site-python" directory to sys.path, if it
|
|
exists, is deprecated (:issue:`19375`).
|
|
|
|
|
|
|
|
Removed
|
|
=======
|
|
|
|
|
|
Operating Systems No Longer Supported
|
|
-------------------------------------
|
|
|
|
Support for the following operating systems has been removed from the source
|
|
and build tools:
|
|
|
|
* OS/2 (:issue:`16135`).
|
|
* Windows 2000 (changeset e52df05b496a).
|
|
* Windows systems where ``COMSPEC`` points to ``command.com`` (:issue:`14470`).
|
|
* VMS (:issue:`16136`).
|
|
|
|
|
|
API and Feature Removals
|
|
------------------------
|
|
|
|
The following obsolete and previously deprecated APIs and features have been
|
|
removed:
|
|
|
|
* The unmaintained ``Misc/TextMate`` and ``Misc/vim`` directories have been
|
|
removed (see the `devguide <http://docs.python.org/devguide>`_
|
|
for suggestions on what to use instead).
|
|
|
|
* The ``SO`` makefile macro is removed (it was replaced by the
|
|
``SHLIB_SUFFIX`` and ``EXT_SUFFIX`` macros) (:issue:`16754`).
|
|
|
|
* The ``PyThreadState.tick_counter`` field has been removed; its value has
|
|
been meaningless since Python 3.2, when the "new GIL" was introduced
|
|
(:issue:`19199`).
|
|
|
|
* ``PyLoader`` and ``PyPycLoader`` have been removed from :mod:`importlib`.
|
|
(Contributed by Taras Lyapun in :issue:`15641`.)
|
|
|
|
* The *strict* argument to :class:`~http.client.HTTPConnection` and
|
|
:class:`~http.client.HTTPSConnection` has been removed. HTTP 0.9-style
|
|
"Simple Responses" are no longer supported.
|
|
|
|
* The deprecated :mod:`urllib.request.Request` getter and setter methods
|
|
``add_data``, ``has_data``, ``get_data``, ``get_type``, ``get_host``,
|
|
``get_selector``, ``set_proxy``, ``get_origin_req_host``, and
|
|
``is_unverifiable`` have been removed (use direct attribute access instead).
|
|
|
|
* Support for loading the deprecated ``TYPE_INT64`` has been removed from
|
|
:mod:`marshal`. (Contributed by Dan Riti in :issue:`15480`.)
|
|
|
|
* :class:`inspect.Signature`: positional-only parameters are now required
|
|
to have a valid name.
|
|
|
|
* :meth:`object.__format__` no longer accepts non-empty format strings, it now
|
|
raises a :exc:`TypeError` instead. Using a non-empty string has been
|
|
deprecated since Python 3.2. This change has been made to prevent a
|
|
situation where previously working (but incorrect) code would start failing
|
|
if an object gained a __format__ method, which means that your code may now
|
|
raise a :exc:`TypeError` if you are using an ``'s'`` format code with objects
|
|
that do not have a __format__ method that handles it. See :issue:`7994` for
|
|
background.
|
|
|
|
* :meth:`difflib.SequenceMatcher.isbjunk` and
|
|
:meth:`difflib.SequenceMatcher.isbpopular` were deprecated in 3.2, and have
|
|
now been removed: use ``x in sm.bjunk`` and
|
|
``x in sm.bpopular``, where *sm* is a :class:`~difflib.SequenceMatcher` object
|
|
(:issue:`13248`).
|
|
|
|
|
|
Code Cleanups
|
|
-------------
|
|
|
|
* The unused and undocumented internal ``Scanner`` class has been removed from
|
|
the :mod:`pydoc` module.
|
|
|
|
* The private and effectively unused ``_gestalt`` module has been removed,
|
|
along with the private :mod:`platform` functions ``_mac_ver_lookup``,
|
|
``_mac_ver_gstalt``, and ``_bcd2str``, which would only have ever been called
|
|
on badly broken OSX systems (see :issue:`18393`).
|
|
|
|
* The hardcoded copies of certain :mod:`stat` constants that were included in
|
|
the :mod:`tarfile` module namespace have been removed.
|
|
|
|
|
|
|
|
Porting to Python 3.4
|
|
=====================
|
|
|
|
This section lists previously described changes and other bugfixes
|
|
that may require changes to your code.
|
|
|
|
|
|
Changes in 'python' Command Behavior
|
|
------------------------------------
|
|
|
|
* In a posix shell, setting the :envvar:`PATH` environment variable to
|
|
an empty value is equivalent to not setting it at all. However, setting
|
|
:envvar:`PYTHONPATH` to an empty value was *not* equivalent to not setting it
|
|
at all: setting :envvar:`PYTHONPATH` to an empty value was equivalent to
|
|
setting it to ``.``, which leads to confusion when reasoning by analogy to
|
|
how :envvar:`PATH` works. The behavior now conforms to the posix convention
|
|
for :envvar:`PATH`.
|
|
|
|
* The [X refs, Y blocks] output of a debug (``--with-pydebug``) build of the
|
|
CPython interpreter is now off by default. It can be re-enabled using the
|
|
``-X showrefcount`` option. (Contributed by Ezio Melotti in :issue:`17323`.)
|
|
|
|
* The python command and most stdlib scripts (as well as :mod:`argparse`) now
|
|
output ``--version`` information to ``stdout`` instead of ``stderr`` (for
|
|
issue list see :ref:`other-improvements-3.4` above).
|
|
|
|
|
|
Changes in the Python API
|
|
-------------------------
|
|
|
|
* The ABCs defined in :mod:`importlib.abc` now either raise the appropriate
|
|
exception or return a default value instead of raising
|
|
:exc:`NotImplementedError` blindly. This will only affect code calling
|
|
:func:`super` and falling through all the way to the ABCs. For compatibility,
|
|
catch both :exc:`NotImplementedError` or the appropriate exception as needed.
|
|
|
|
* The module type now initializes the :attr:`__package__` and :attr:`__loader__`
|
|
attributes to ``None`` by default. To determine if these attributes were set
|
|
in a backwards-compatible fashion, use e.g.
|
|
``getattr(module, '__loader__', None) is not None``. (:issue:`17115`.)
|
|
|
|
* :meth:`importlib.util.module_for_loader` now sets ``__loader__`` and
|
|
``__package__`` unconditionally to properly support reloading. If this is not
|
|
desired then you will need to set these attributes manually. You can use
|
|
:func:`importlib.util.module_to_load` for module management.
|
|
|
|
* Import now resets relevant attributes (e.g. ``__name__``, ``__loader__``,
|
|
``__package__``, ``__file__``, ``__cached__``) unconditionally when reloading.
|
|
Note that this restores a pre-3.3 behavior in that it means a module is
|
|
re-found when re-loaded (:issue:`19413`).
|
|
|
|
* Frozen packages no longer set ``__path__`` to a list containing the package
|
|
name, they now set it to an empty list. The previous behavior could cause
|
|
the import system to do the wrong thing on submodule imports if there was
|
|
also a directory with the same name as the frozen package. The correct way
|
|
to determine if a module is a package or not is to use ``hasattr(module,
|
|
'__path__')`` (:issue:`18065`).
|
|
|
|
* Frozen modules no longer define a ``__file__`` attribute. It's semantically
|
|
incorrect for frozen modules to set the attribute as they are not loaded from
|
|
any explicit location. If you must know that a module comes from frozen code
|
|
then you can see if the module's ``__spec__.location`` is set to ``'frozen'``,
|
|
check if the loader is a subclass of
|
|
:class:`importlib.machinery.FrozenImporter`,
|
|
or if Python 2 compatibility is necessary you can use :func:`imp.is_frozen`.
|
|
|
|
* :func:`py_compile.compile` now raises :exc:`FileExistsError` if the file path
|
|
it would write to is a symlink or a non-regular file. This is to act as a
|
|
warning that import will overwrite those files with a regular file regardless
|
|
of what type of file path they were originally.
|
|
|
|
* :meth:`importlib.abc.SourceLoader.get_source` no longer raises
|
|
:exc:`ImportError` when the source code being loaded triggers a
|
|
:exc:`SyntaxError` or :exc:`UnicodeDecodeError`. As :exc:`ImportError` is
|
|
meant to be raised only when source code cannot be found but it should, it was
|
|
felt to be over-reaching/overloading of that meaning when the source code is
|
|
found but improperly structured. If you were catching ImportError before and
|
|
wish to continue to ignore syntax or decoding issues, catch all three
|
|
exceptions now.
|
|
|
|
* :func:`functools.update_wrapper` and :func:`functools.wraps` now correctly
|
|
set the ``__wrapped__`` attribute to the function being wrapped, even if
|
|
that function also had its ``__wrapped__`` attribute set. This means
|
|
``__wrapped__`` attributes now correctly link a stack of decorated
|
|
functions rather than every ``__wrapped__`` attribute in the chain
|
|
referring to the innermost function. Introspection libraries that
|
|
assumed the previous behaviour was intentional can use
|
|
:func:`inspect.unwrap` to access the first function in the chain that has
|
|
no ``__wrapped__`` attribute.
|
|
|
|
* :func:`inspect.getfullargspec` has been reimplemented on top of
|
|
:func:`inspect.signature` and hence handles a much wider variety of callable
|
|
objects than it did in the past. It is expected that additional builtin and
|
|
extension module callables will gain signature metadata over the course of
|
|
the Python 3.4 series. Code that assumes that
|
|
:func:`inspect.getfullargspec` will fail on non-Python callables may need
|
|
to be adjusted accordingly.
|
|
|
|
* :class:`importlib.machinery.PathFinder` now passes on the current working
|
|
directory to objects in :data:`sys.path_hooks` for the empty string. This
|
|
results in :data:`sys.path_importer_cache` never containing ``''``, thus
|
|
iterating through :data:`sys.path_importer_cache` based on :data:`sys.path`
|
|
will not find all keys. A module's ``__file__`` when imported in the current
|
|
working directory will also now have an absolute path, including when using
|
|
``-m`` with the interpreter (except for ``__main__.__file__`` when a script
|
|
has been executed directly using a relative path) (Contributed by Brett
|
|
Cannon in :issue:`18416`). is specified on the command-line)
|
|
(:issue:`18416`).
|
|
|
|
* The removal of the *strict* argument to :class:`~http.client.HTTPConnection`
|
|
and :class:`~http.client.HTTPSConnection` changes the meaning of the
|
|
remaining arguments if you are specifying them positionally rather than by
|
|
keyword. If you've been paying attention to deprecation warnings your code
|
|
should already be specifying any additional arguments via keywords.
|
|
|
|
* Strings between ``from __future__ import ...`` statements now *always* raise
|
|
a :exc:`SyntaxError`. Previously if there was no leading docstring, an
|
|
interstitial string would sometimes be ignored. This brings CPython into
|
|
compliance with the language spec; Jython and PyPy already were.
|
|
(:issue:`17434`).
|
|
|
|
* :meth:`ssl.SSLSocket.getpeercert` and :meth:`ssl.SSLSocket.do_handshake`
|
|
now raise an :exc:`OSError` with ``ENOTCONN`` when the ``SSLSocket`` is not
|
|
connected, instead of the previous behavior of raising an
|
|
:exc:`AttributeError`. In addition, :meth:`~ssl.SSLSocket.getpeercert`
|
|
will raise a :exc:`ValueError` if the handshake has not yet been done.
|
|
|
|
* :func:`base64.b32decode` now raises a :exc:`binascii.Error` when the
|
|
input string contains non-b32-alphabet characters, instead of a
|
|
:exc:`TypeError`. This particular :exc:`TypeError` was missed when the other
|
|
:exc:`TypeError`\ s were converted. (Contributed by Serhiy Storchaka in
|
|
:issue:`18011`.) Note: this change was also inadvertently applied in Python
|
|
3.3.3.
|
|
|
|
* The :attr:`~cgi.FieldStorage.file` attribute is now automatically closed when
|
|
the creating :class:`cgi.FieldStorage` instance is garbage collected. If you
|
|
were pulling the file object out separately from the :class:`cgi.FieldStorage`
|
|
instance and not keeping the instance alive, then you should either store the
|
|
entire :class:`cgi.FieldStorage` instance or read the contents of the file
|
|
before the :class:`cgi.FieldStorage` instance is garbage collected.
|
|
|
|
* Calling ``read`` or ``write`` on a closed SSL socket now raises an
|
|
informative :exc:`ValueError` rather than the previous more mysterious
|
|
:exc:`AttributeError` (:issue:`9177`).
|
|
|
|
* :meth:`slice.indices` no longer produces an :exc:`OverflowError` for huge
|
|
values. As a consequence of this fix, :meth:`slice.indices` now raises a
|
|
:exc:`ValueError` if given a negative length; previously it returned nonsense
|
|
values (:issue:`14794`).
|
|
|
|
* The :class:`complex` constructor, unlike the :mod:`cmath` functions, was
|
|
incorrectly accepting :class:`float` values if an object's ``__complex__``
|
|
special method returned one. This now raises a :exc:`TypeError`.
|
|
(:issue:`16290`.)
|
|
|
|
* The :class:`int` constructor in 3.2 and 3.3 erroneously accepts :class:`float`
|
|
values for the *base* parameter. It is unlikely anyone was doing this, but
|
|
if so, it will now raise a :exc:`TypeError` (:issue:`16772`).
|
|
|
|
* Defaults for keyword-only arguments are now evaluated *after* defaults for
|
|
regular keyword arguments, instead of before. Hopefully no one wrote any
|
|
code that depends on the previous buggy behavior (:issue:`16967`).
|
|
|
|
* Stale thread states are now cleared after :func:`~os.fork`. This may cause
|
|
some system resources to be released that previously were incorrectly kept
|
|
perpetually alive (for example, database connections kept in thread-local
|
|
storage). (:issue:`17094`.)
|
|
|
|
* Parameter names in ``__annotations__`` dicts are now mangled properly,
|
|
similarly to ``__kwdefaults__``. (Contributed by Yury Selivanov in
|
|
:issue:`20625`).
|
|
|
|
* :attr:`hashlib.hash.name` now always returns the identifier in lower case.
|
|
Previously some builtin hashes had uppercase names, but now that it is a
|
|
formal public interface the naming has been made consistent (:issue:`18532`).
|
|
|
|
* Because :mod:`unittest.TestSuite` now drops references to tests after they
|
|
are run, test harnesses that re-use a :class:`~unittest.TestSuite` to re-run
|
|
a set of tests may fail. Test suites should not be re-used in this fashion
|
|
since it means state is retained between test runs, breaking the test
|
|
isolation that :mod:`unittest` is designed to provide. However, if the lack
|
|
of isolation is considered acceptable, the old behavior can be restored by
|
|
creating a :mod:`~unittest.TestSuite` subclass that defines a
|
|
``_removeTestAtIndex`` method that does nothing (see
|
|
:meth:`.TestSuite.__iter__`) (:issue:`11798`).
|
|
|
|
* :mod:`unittest` now uses :mod:`argparse` for command line parsing. There are
|
|
certain invalid command forms that used to work that are no longer allowed;
|
|
in theory this should not cause backward compatibility issues since the
|
|
disallowed command forms didn't make any sense and are unlikely to be in use.
|
|
|
|
* The :func:`re.split`, :func:`re.findall`, and :func:`re.sub` functions, and
|
|
the :meth:`~re.match.group` and :meth:`~re.match.groups` methods of
|
|
``match`` objects now always return a *bytes* object when the string
|
|
to be matched is a :term:`bytes-like object`. Previously the return type
|
|
matched the input type, so if your code was depending on the return value
|
|
being, say, a ``bytearray``, you will need to change your code.
|
|
|
|
* :mod:`audioop` functions now raise an error immediately if passed string
|
|
input, instead of failing randomly later on (:issue:`16685`).
|
|
|
|
* The new *convert_charrefs* argument to :class:`~html.parser.HTMLParser`
|
|
currently defaults to ``False`` for backward compatibility, but will
|
|
eventually be changed to default to ``True``. It is recommended that you add
|
|
this keyword, with the appropriate value, to any
|
|
:class:`~html.parser.HTMLParser` calls in your code (:issue:`13633`).
|
|
|
|
* Since the *digestmod* argument to the :func:`hmac.new` function will in the
|
|
future have no default, all calls to :func:`hmac.new` should be changed to
|
|
explicitly specify a *digestmod* (:issue:`17276`).
|
|
|
|
* Calling :func:`sysconfig.get_config_var` with the ``SO`` key, or looking
|
|
``SO`` up in the results of a call to :func:`sysconfig.get_config_vars`
|
|
is deprecated. This key should be replaced by ``EXT_SUFFIX`` or
|
|
``SHLIB_SUFFIX``, depending on the context (:issue:`19555`).
|
|
|
|
* Any calls to ``open`` functions that specify ``U`` should be modified.
|
|
``U`` is ineffective in Python3 and will eventually raise an error if used.
|
|
Depending on the function, the equivalent of its old Python2 behavior can be
|
|
achieved using either a *newline* argument, or if necessary by wrapping the
|
|
stream in :mod:`~io.TextIOWrapper` to use its *newline* argument
|
|
(:issue:`15204`).
|
|
|
|
* If you use :ref:`pyvenv <scripts-pyvenv>` in a script and desire that pip
|
|
*not* be installed, you must add ``--without-pip`` to your command
|
|
invocation.
|
|
|
|
* The default behavior of :func:`json.dump` and :func:`json.dumps` when
|
|
an indent is specified has changed: it no longer produces trailing
|
|
spaces after the item separating commas at the ends of lines. This
|
|
will matter only if you have tests that are doing white-space-sensitive
|
|
comparisons of such output (:issue:`16333`).
|
|
|
|
* :mod:`doctest` now looks for doctests in extension module ``__doc__``
|
|
strings, so if your doctest test discovery includes extension modules that
|
|
have things that look like doctests in them you may see test failures you've
|
|
never seen before when running your tests (:issue:`3158`).
|
|
|
|
* The :mod:`collections.abc` module has been slightly refactored as
|
|
part of the Python startup improvements. As a consequence of this, it is no
|
|
longer the case that importing :mod:`collections` automatically imports
|
|
:mod:`collections.abc`. If your program depended on the (undocumented)
|
|
implicit import, you will need to add an explicit ``import collections.abc``
|
|
(:issue:`20784`).
|
|
|
|
|
|
Changes in the C API
|
|
--------------------
|
|
|
|
* :c:func:`PyEval_EvalFrameEx`, :c:func:`PyObject_Repr`, and
|
|
:c:func:`PyObject_Str`, along with some other internal C APIs, now include
|
|
a debugging assertion that ensures they are not used in situations where
|
|
they may silently discard a currently active exception. In cases where
|
|
discarding the active exception is expected and desired (for example,
|
|
because it has already been saved locally with :c:func:`PyErr_Fetch` or
|
|
is being deliberately replaced with a different exception), an explicit
|
|
:c:func:`PyErr_Clear` call will be needed to avoid triggering the
|
|
assertion when invoking these operations (directly or indirectly) and
|
|
running against a version of Python that is compiled with assertions
|
|
enabled.
|
|
|
|
* :c:func:`PyErr_SetImportError` now sets :exc:`TypeError` when its **msg**
|
|
argument is not set. Previously only ``NULL`` was returned with no exception
|
|
set.
|
|
|
|
* The result of the :c:data:`PyOS_ReadlineFunctionPointer` callback must
|
|
now be a string allocated by :c:func:`PyMem_RawMalloc` or
|
|
:c:func:`PyMem_RawRealloc`, or *NULL* if an error occurred, instead of a
|
|
string allocated by :c:func:`PyMem_Malloc` or :c:func:`PyMem_Realloc`
|
|
(:issue:`16742`)
|
|
|
|
* :c:func:`PyThread_set_key_value` now always set the value. In Python
|
|
3.3, the function did nothing if the key already exists (if the current
|
|
value is a non-NULL pointer).
|
|
|
|
* The ``f_tstate`` (thread state) field of the :c:type:`PyFrameObject`
|
|
structure has been removed to fix a bug: see :issue:`14432` for the
|
|
rationale.
|