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ReStructuredText
318 lines
10 KiB
ReStructuredText
****************************
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What's New In Python 3.4
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****************************
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.. :Author: Someone <email>
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(uncomment if there is a principal author)
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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 TBD.
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For full details, see the
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`changelog <http://docs.python.org/3.4/whatsnew/changelog.html>`_.
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.. note:: Prerelease users should be aware that this document is currently in
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draft form. It will be updated substantially as Python 3.4 moves towards
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release, so it's worth checking back even after reading earlier versions.
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.. seealso::
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.. :pep:`4XX` - 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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* None yet.
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New library modules:
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* :mod:`enum`: Implementation of the :pep:`435`.
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New built-in features:
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* None yet.
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Implementation improvements:
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* A more efficient :mod:`marshal` format <http://bugs.python.org/issue16475>.
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Significantly Improved Library Modules:
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* SHA-3 (Keccak) support for :mod:`hashlib`.
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* TLSv1.1 and TLSv1.2 support for :mod:`ssl`.
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Security improvements:
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* None yet.
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Please read on for a comprehensive list of user-facing changes.
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PEP 445: Add new APIs to customize Python memory allocators
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===========================================================
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The :pep:`445` adds new Application Programming Interfaces (API) to customize
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Python memory allocators.
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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 6.2.
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* :func:`min` and :func:`max` now accept a *default* argument that can be used
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to specify the value they return if the iterable they are evaluating has no
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elements. Contributed by Julian Berman in :issue:`18111`.
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New Modules
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===========
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.. module name
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.. -----------
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* None yet.
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Improved Modules
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================
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dis
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---
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The :mod:`dis` module is now built around an :class:`Instruction` class that
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provides details of individual bytecode operations and a
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:func:`get_instructions` iterator that emits the Instruction stream for a
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given piece of Python code. The various display tools in the :mod:`dis`
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module have been updated to be based on these new components.
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The new :class:`dis.Bytecode` class provides an object-oriented API for
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inspecting bytecode, both in human-readable form and for iterating over
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instructions.
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(Contributed by Nick Coghlan, Ryan Kelly and Thomas Kluyver in :issue:`11816`)
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doctest
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-------
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Added :data:`~doctest.FAIL_FAST` flag to halt test running as soon as the first
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failure is detected. (Contributed by R. David Murray and Daniel Urban in
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:issue:`16522`.)
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Updated the doctest command line interface to use :mod:`argparse`, and added
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``-o`` and ``-f`` options to the interface. ``-o`` allows doctest options to
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be specified on the command line, and ``-f`` is a shorthand for ``-o
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FAIL_FAST`` (to parallel the similar option supported by the :mod:`unittest`
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CLI). (Contributed by R. David Murray in :issue:`11390`.)
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functools
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---------
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New :func:`functools.singledispatch` decorator: see the :pep:`443`.
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smtplib
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-------
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:exc:`~smtplib.SMTPException` is now a subclass of :exc:`OSError`, which allows
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both socket level errors and SMTP protocol level errors to be caught in one
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try/except statement by code that only cares whether or not an error occurred.
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(:issue:`2118`).
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ssl
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---
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TLSv1.1 and TLSv1.2 support (Contributed by Michele Orrù and Antoine Pitrou
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in :issue:`16692`)
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New diagnostic functions :func:`~ssl.get_default_verify_paths`,
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:meth:`~ssl.SSLContext.cert_store_stats` and
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:meth:`~ssl.SSLContext.get_ca_certs`
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Add :func:`ssl.enum_cert_store` to retrieve certificates and CRL from Windows'
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cert store.
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(Contributed by Christian Heimes in :issue:`18143`, :issue:`18147` and
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:issue:`17134`)
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wave
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----
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The :meth:`~wave.getparams` method now returns a namedtuple rather than a
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plain tuple. (Contributed by Claudiu Popa in :issue:`17487`.)
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stat
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---
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The stat module is now backed by a C implementation in :mod:`_stat`. A C
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implementation is required as most of the values aren't standardized and
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platform-dependent. (Contributed by Christian Heimes in :issue:`11016`.)
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Optimizations
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=============
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Major performance enhancements have been added:
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* The UTF-32 decoder is now 3x to 4x faster.
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Build and C API Changes
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=======================
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Changes to Python's build process and to the C API include:
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* None yet.
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Deprecated
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==========
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Unsupported Operating Systems
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-----------------------------
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* None yet.
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Deprecated Python modules, functions and methods
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------------------------------------------------
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* :meth:`difflib.SequenceMatcher.isbjunk` and
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:meth:`difflib.SequenceMatcher.isbpopular` were removed: use ``x in sm.bjunk`` and
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``x in sm.bpopular``, where *sm* is a :class:`~difflib.SequenceMatcher` object.
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* :func:`importlib.util.module_for_loader` is pending deprecation. Using
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:func:`importlib.util.module_to_load` and
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:meth:`importlib.abc.Loader.init_module_attrs` allows subclasses of a loader
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to more easily customize module loading.
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* The :mod:`imp` module is pending deprecation. To keep compatibility with
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Python 2/3 code bases, the module's removal is currently not scheduled.
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Deprecated functions and types of the C API
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-------------------------------------------
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* None yet.
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Deprecated features
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-------------------
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* None yet.
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Porting to Python 3.4
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=====================
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This section lists previously described changes and other bugfixes
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that may require changes to your code.
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* The ABCs defined in :mod:`importlib.abc` now either raise the appropriate
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exception or return a default value instead of raising
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:exc:`NotImplementedError` blindly. This will only affect code calling
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:func:`super` and falling through all the way to the ABCs. For compatibility,
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catch both :exc:`NotImplementedError` or the appropriate exception as needed.
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* The module type now initializes the :attr:`__package__` and :attr:`__loader__`
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attributes to ``None`` by default. To determine if these attributes were set
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in a backwards-compatible fashion, use e.g.
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``getattr(module, '__loader__', None) is not None``.
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* :meth:`importlib.util.module_for_loader` now sets ``__loader__`` and
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``__package__`` unconditionally to properly support reloading. If this is not
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desired then you will need to set these attributes manually. You can use
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:func:`importlib.util.module_to_load` for module management.
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* Import now resets relevant attributes (e.g. ``__name__``, ``__loader__``,
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``__package__``, ``__file__``, ``__cached__``) unconditionally when reloading.
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* Frozen packages no longer set ``__path__`` to a list containg the package name
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but an empty list instead. Determing if a module is a package should be done
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using ``hasattr(module, '__path__')``.
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* :c:func:`PyErr_SetImportError` now sets :exc:`TypeError` when its **msg**
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argument is not set. Previously only ``NULL`` was returned with no exception
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set.
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* :func:`py_compile.compile` now raises :exc:`FileExistsError` if the file path
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it would write to is a symlink or a non-regular file. This is to act as a
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warning that import will overwrite those files with a regular file regardless
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of what type of file path they were originally.
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* :meth:`importlib.abc.SourceLoader.get_source` no longer raises
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:exc:`ImportError` when the source code being loaded triggers a
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:exc:`SyntaxError` or :exc:`UnicodeDecodeError`. As :exc:`ImportError` is
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meant to be raised only when source code cannot be found but it should, it was
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felt to be over-reaching/overloading of that meaning when the source code is
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found but improperly structured. If you were catching ImportError before and
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wish to continue to ignore syntax or decoding issues, catch all three
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exceptions now.
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