--- /dev/null
- * The ``--with-optimizations`` configure flag has been added. Turning it on
+****************************
+ What's New In Python 3.6
+****************************
+
+:Release: |release|
+:Date: |today|
+:Editors: Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io>
+
+.. Rules for maintenance:
+
+ * Anyone can add text to this document. Do not spend very much time
+ on the wording of your changes, because your text will probably
+ get rewritten to some degree.
+
+ * The maintainer will go through Misc/NEWS periodically and add
+ changes; it's therefore more important to add your changes to
+ Misc/NEWS than to this file.
+
+ * This is not a complete list of every single change; completeness
+ is the purpose of Misc/NEWS. Some changes I consider too small
+ or esoteric to include. If such a change is added to the text,
+ I'll just remove it. (This is another reason you shouldn't spend
+ too much time on writing your addition.)
+
+ * If you want to draw your new text to the attention of the
+ maintainer, add 'XXX' to the beginning of the paragraph or
+ section.
+
+ * It's OK to just add a fragmentary note about a change. For
+ example: "XXX Describe the transmogrify() function added to the
+ socket module." The maintainer will research the change and
+ write the necessary text.
+
+ * You can comment out your additions if you like, but it's not
+ necessary (especially when a final release is some months away).
+
+ * Credit the author of a patch or bugfix. Just the name is
+ sufficient; the e-mail address isn't necessary.
+
+ * It's helpful to add the bug/patch number as a comment:
+
+ XXX Describe the transmogrify() function added to the socket
+ module.
+ (Contributed by P.Y. Developer in :issue:`12345`.)
+
+ This saves the maintainer the effort of going through the Mercurial log
+ when researching a change.
+
+.. note::
+
+ Prerelease users should be aware that this document is currently in draft
+ form. It will be updated substantially as Python 3.6 moves towards release,
+ so it's worth checking back even after reading earlier versions.
+
+This article explains the new features in Python 3.6, compared to 3.5.
+
+.. seealso::
+
+ :pep:`494` - Python 3.6 Release Schedule
+
+
+Summary -- Release highlights
+=============================
+
+.. This section singles out the most important changes in Python 3.6.
+ Brevity is key.
+
+New syntax features:
+
+* :ref:`PEP 498 <whatsnew36-pep498>`, formatted string literals.
+
+* :ref:`PEP 515 <whatsnew36-pep515>`, underscores in numeric literals.
+
+* :ref:`PEP 526 <whatsnew36-pep526>`, syntax for variable annotations.
+
+* :ref:`PEP 525 <whatsnew36-pep525>`, asynchronous generators.
+
+* :ref:`PEP 530 <whatsnew36-pep530>`: asynchronous comprehensions.
+
+
+New library modules:
+
+* :mod:`secrets`: :ref:`PEP 506 -- Adding A Secrets Module To The Standard Library <whatsnew36-pep506>`.
+
+
+CPython implementation improvements:
+
+* The :ref:`dict <typesmapping>` type has been reimplemented to use
+ a :ref:`faster, more compact representation <whatsnew36-compactdict>`
+ similar to the `PyPy dict implementation`_. This resulted in dictionaries
+ using 20% to 25% less memory when compared to Python 3.5.
+
+* Customization of class creation has been simplified with the
+ :ref:`new protocol <whatsnew36-pep487>`.
+
+* The class attribute definition order is
+ :ref:`now preserved <whatsnew36-pep520>`.
+
+* The order of elements in ``**kwargs`` now
+ :ref:`corresponds to the order <whatsnew36-pep468>` in which keyword
+ arguments were passed to the function.
+
+* DTrace and SystemTap :ref:`probing support <whatsnew36-tracing>` has
+ been added.
+
+* The new :ref:`PYTHONMALLOC <whatsnew36-pythonmalloc>` environment variable
+ can now be used to debug the interpreter memory allocation and access
+ errors.
+
+
+Significant improvements in the standard library:
+
+* The :mod:`asyncio` module has received new features, significant
+ usability and performance improvements, and a fair amount of bug fixes.
+ Starting with Python 3.6 the ``asyncio`` module is no longer provisional
+ and its API is considered stable.
+
+* A new :ref:`file system path protocol <whatsnew36-pep519>` has been
+ implemented to support :term:`path-like objects <path-like object>`.
+ All standard library functions operating on paths have been updated to
+ work with the new protocol.
+
+* The :mod:`datetime` module has gained support for
+ :ref:`Local Time Disambiguation <whatsnew36-pep495>`.
+
+* The :mod:`typing` module received a number of
+ :ref:`improvements <whatsnew36-typing>` and is no longer provisional.
+
+* The :mod:`tracemalloc` module has been significantly reworked
+ and is now used to provide better output for :exc:`ResourceWarning`
+ as well as provide better diagnostics for memory allocation errors.
+ See the :ref:`PYTHONMALLOC section <whatsnew36-pythonmalloc>` for more
+ information.
+
+
+Security improvements:
+
+* The new :mod:`secrets` module has been added to simplify the generation of
+ cryptographically strong pseudo-random numbers suitable for
+ managing secrets such as account authentication, tokens, and similar.
+
+* On Linux, :func:`os.urandom` now blocks until the system urandom entropy
+ pool is initialized to increase the security. See the :pep:`524` for the
+ rationale.
+
+* The :mod:`hashlib` and :mod:`ssl` modules now support OpenSSL 1.1.0.
+
+* The default settings and feature set of the :mod:`ssl` module have been
+ improved.
+
+* The :mod:`hashlib` module received support for the BLAKE2, SHA-3 and SHAKE
+ hash algorithms and the :func:`~hashlib.scrypt` key derivation function.
+
+
+Windows improvements:
+
+* :ref:`PEP 528 <whatsnew36-pep529>` and :ref:`PEP 529 <whatsnew36-pep529>`,
+ Windows filesystem and console encoding changed to UTF-8.
+
+* The ``py.exe`` launcher, when used interactively, no longer prefers
+ Python 2 over Python 3 when the user doesn't specify a version (via
+ command line arguments or a config file). Handling of shebang lines
+ remains unchanged - "python" refers to Python 2 in that case.
+
+* ``python.exe`` and ``pythonw.exe`` have been marked as long-path aware,
+ which means that when the 260 character path limit may no longer apply.
+ See :ref:`removing the MAX_PATH limitation <max-path>` for details.
+
+* A ``._pth`` file can be added to force isolated mode and fully specify
+ all search paths to avoid registry and environment lookup. See
+ :ref:`the documentation <finding_modules>` for more information.
+
+* A ``python36.zip`` file now works as a landmark to infer
+ :envvar:`PYTHONHOME`. See :ref:`the documentation <finding_modules>` for
+ more information.
+
+
+.. _PyPy dict implementation: https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html
+
+
+New Features
+============
+
+.. _whatsnew36-pep498:
+
+PEP 498: Formatted string literals
+----------------------------------
+
+:pep:`498` introduces a new kind of string literals: *f-strings*, or
+:ref:`formatted string literals <f-strings>`.
+
+Formatted string literals are prefixed with ``'f'`` and are similar to
+the format strings accepted by :meth:`str.format`. They contain replacement
+fields surrounded by curly braces. The replacement fields are expressions,
+which are evaluated at run time, and then formatted using the
+:func:`format` protocol::
+
+ >>> name = "Fred"
+ >>> f"He said his name is {name}."
+ 'He said his name is Fred.'
+ >>> width = 10
+ >>> precision = 4
+ >>> value = decimal.Decimal("12.34567")
+ >>> f"result: {value:{width}.{precision}}" # nested fields
+ 'result: 12.35'
+
+.. seealso::
+
+ :pep:`498` -- Literal String Interpolation.
+ PEP written and implemented by Eric V. Smith.
+
+ :ref:`Feature documentation <f-strings>`.
+
+
+.. _whatsnew36-pep526:
+
+PEP 526: Syntax for variable annotations
+----------------------------------------
+
+:pep:`484` introduced the standard for type annotations of function
+parameters, a.k.a. type hints. This PEP adds syntax to Python for annotating
+the types of variables including class variables and instance variables::
+
+ primes: List[int] = []
+
+ captain: str # Note: no initial value!
+
+ class Starship:
+ stats: Dict[str, int] = {}
+
+Just as for function annotations, the Python interpreter does not attach any
+particular meaning to variable annotations and only stores them in the
+``__annotations__`` attribute of a class or module.
+
+In contrast to variable declarations in statically typed languages,
+the goal of annotation syntax is to provide an easy way to specify structured
+type metadata for third party tools and libraries via the abstract syntax tree
+and the ``__annotations__`` attribute.
+
+.. seealso::
+
+ :pep:`526` -- Syntax for variable annotations.
+ PEP written by Ryan Gonzalez, Philip House, Ivan Levkivskyi, Lisa Roach,
+ and Guido van Rossum. Implemented by Ivan Levkivskyi.
+
+ Tools that use or will use the new syntax:
+ `mypy <http://github.com/python/mypy>`_,
+ `pytype <http://github.com/google/pytype>`_, PyCharm, etc.
+
+
+.. _whatsnew36-pep515:
+
+PEP 515: Underscores in Numeric Literals
+----------------------------------------
+
+:pep:`515` adds the ability to use underscores in numeric literals for
+improved readability. For example::
+
+ >>> 1_000_000_000_000_000
+ 1000000000000000
+ >>> 0x_FF_FF_FF_FF
+ 4294967295
+
+Single underscores are allowed between digits and after any base
+specifier. Leading, trailing, or multiple underscores in a row are not
+allowed.
+
+The :ref:`string formatting <formatspec>` language also now has support
+for the ``'_'`` option to signal the use of an underscore for a thousands
+separator for floating point presentation types and for integer
+presentation type ``'d'``. For integer presentation types ``'b'``,
+``'o'``, ``'x'``, and ``'X'``, underscores will be inserted every 4
+digits::
+
+ >>> '{:_}'.format(1000000)
+ '1_000_000'
+ >>> '{:_x}'.format(0xFFFFFFFF)
+ 'ffff_ffff'
+
+.. seealso::
+
+ :pep:`515` -- Underscores in Numeric Literals
+ PEP written by Georg Brandl and Serhiy Storchaka.
+
+
+.. _whatsnew36-pep525:
+
+PEP 525: Asynchronous Generators
+--------------------------------
+
+:pep:`492` introduced support for native coroutines and ``async`` / ``await``
+syntax to Python 3.5. A notable limitation of the Python 3.5 implementation
+is that it was not possible to use ``await`` and ``yield`` in the same
+function body. In Python 3.6 this restriction has been lifted, making it
+possible to define *asynchronous generators*::
+
+ async def ticker(delay, to):
+ """Yield numbers from 0 to *to* every *delay* seconds."""
+ for i in range(to):
+ yield i
+ await asyncio.sleep(delay)
+
+The new syntax allows for faster and more concise code.
+
+.. seealso::
+
+ :pep:`525` -- Asynchronous Generators
+ PEP written and implemented by Yury Selivanov.
+
+
+.. _whatsnew36-pep530:
+
+PEP 530: Asynchronous Comprehensions
+------------------------------------
+
+:pep:`530` adds support for using ``async for`` in list, set, dict
+comprehensions and generator expressions::
+
+ result = [i async for i in aiter() if i % 2]
+
+Additionally, ``await`` expressions are supported in all kinds
+of comprehensions::
+
+ result = [await fun() for fun in funcs if await condition()]
+
+.. seealso::
+
+ :pep:`530` -- Asynchronous Comprehensions
+ PEP written and implemented by Yury Selivanov.
+
+
+.. _whatsnew36-pep487:
+
+PEP 487: Simpler customization of class creation
+------------------------------------------------
+
+It is now possible to customize subclass creation without using a metaclass.
+The new ``__init_subclass__`` classmethod will be called on the base class
+whenever a new subclass is created::
+
+ class PluginBase:
+ subclasses = []
+
+ def __init_subclass__(cls, **kwargs):
+ super().__init_subclass__(**kwargs)
+ cls.subclasses.append(cls)
+
+ class Plugin1(PluginBase):
+ pass
+
+ class Plugin2(PluginBase):
+ pass
+
+.. seealso::
+
+ :pep:`487` -- Simpler customization of class creation
+ PEP written and implemented by Martin Teichmann.
+
+ :ref:`Feature documentation <class-customization>`
+
+
+.. _whatsnew36-pep487-descriptors:
+
+PEP 487: Descriptor Protocol Enhancements
+-----------------------------------------
+
+:pep:`487` extends the descriptor protocol has to include the new optional
+:meth:`~object.__set_name__` method. Whenever a new class is defined, the new
+method will be called on all descriptors included in the definition, providing
+them with a reference to the class being defined and the name given to the
+descriptor within the class namespace. In other words, instances of
+descriptors can now know the attribute name of the descriptor in the
+owner class::
+
+ class IntField:
+ def __get__(self, instance, owner):
+ return instance.__dict__[self.name]
+
+ def __set__(self, instance, value):
+ if not isinstance(value, int):
+ raise ValueError(f'expecting integer in {self.name}')
+ instance.__dict__[self.name] = value
+
+ # this is the new initializer:
+ def __set_name__(self, owner, name):
+ self.name = name
+
+ class Model:
+ int_field = IntField()
+
+
+.. seealso::
+
+ :pep:`487` -- Simpler customization of class creation
+ PEP written and implemented by Martin Teichmann.
+
+ :ref:`Feature documentation <descriptors>`
+
+
+.. _whatsnew36-pep519:
+
+PEP 519: Adding a file system path protocol
+-------------------------------------------
+
+File system paths have historically been represented as :class:`str`
+or :class:`bytes` objects. This has led to people who write code which
+operate on file system paths to assume that such objects are only one
+of those two types (an :class:`int` representing a file descriptor
+does not count as that is not a file path). Unfortunately that
+assumption prevents alternative object representations of file system
+paths like :mod:`pathlib` from working with pre-existing code,
+including Python's standard library.
+
+To fix this situation, a new interface represented by
+:class:`os.PathLike` has been defined. By implementing the
+:meth:`~os.PathLike.__fspath__` method, an object signals that it
+represents a path. An object can then provide a low-level
+representation of a file system path as a :class:`str` or
+:class:`bytes` object. This means an object is considered
+:term:`path-like <path-like object>` if it implements
+:class:`os.PathLike` or is a :class:`str` or :class:`bytes` object
+which represents a file system path. Code can use :func:`os.fspath`,
+:func:`os.fsdecode`, or :func:`os.fsencode` to explicitly get a
+:class:`str` and/or :class:`bytes` representation of a path-like
+object.
+
+The built-in :func:`open` function has been updated to accept
+:class:`os.PathLike` objects as have all relevant functions in the
+:mod:`os` and :mod:`os.path` modules, as well as most functions and
+classes in the standard library. The :class:`os.DirEntry` class
+and relevant classes in :mod:`pathlib` have also been updated to
+implement :class:`os.PathLike`.
+
+The hope in is that updating the fundamental functions for operating
+on file system paths will lead to third-party code to implicitly
+support all :term:`path-like objects <path-like object>` without any
+code changes or at least very minimal ones (e.g. calling
+:func:`os.fspath` at the beginning of code before operating on a
+path-like object).
+
+Here are some examples of how the new interface allows for
+:class:`pathlib.Path` to be used more easily and transparently with
+pre-existing code::
+
+ >>> import pathlib
+ >>> with open(pathlib.Path("README")) as f:
+ ... contents = f.read()
+ ...
+ >>> import os.path
+ >>> os.path.splitext(pathlib.Path("some_file.txt"))
+ ('some_file', '.txt')
+ >>> os.path.join("/a/b", pathlib.Path("c"))
+ '/a/b/c'
+ >>> import os
+ >>> os.fspath(pathlib.Path("some_file.txt"))
+ 'some_file.txt'
+
+(Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.)
+
+.. seealso::
+
+ :pep:`519` -- Adding a file system path protocol
+ PEP written by Brett Cannon and Koos Zevenhoven.
+
+
+.. _whatsnew36-pep495:
+
+PEP 495: Local Time Disambiguation
+----------------------------------
+
+In most world locations, there have been and will be times when local clocks
+are moved back. In those times, intervals are introduced in which local
+clocks show the same time twice in the same day. In these situations, the
+information displayed on a local clock (or stored in a Python datetime
+instance) is insufficient to identify a particular moment in time.
+
+:pep:`495` adds the new *fold* attribute to instances of
+:class:`datetime.datetime` and :class:`datetime.time` classes to differentiate
+between two moments in time for which local times are the same::
+
+ >>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
+ >>> for i in range(4):
+ ... u = u0 + i*HOUR
+ ... t = u.astimezone(Eastern)
+ ... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
+ ...
+ 04:00:00 UTC = 00:00:00 EDT 0
+ 05:00:00 UTC = 01:00:00 EDT 0
+ 06:00:00 UTC = 01:00:00 EST 1
+ 07:00:00 UTC = 02:00:00 EST 0
+
+The values of the :attr:`fold <datetime.datetime.fold>` attribute have the
+value ``0`` for all instances except those that represent the second
+(chronologically) moment in time in an ambiguous case.
+
+.. seealso::
+
+ :pep:`495` -- Local Time Disambiguation
+ PEP written by Alexander Belopolsky and Tim Peters, implementation
+ by Alexander Belopolsky.
+
+
+.. _whatsnew36-pep529:
+
+PEP 529: Change Windows filesystem encoding to UTF-8
+----------------------------------------------------
+
+Representing filesystem paths is best performed with str (Unicode) rather than
+bytes. However, there are some situations where using bytes is sufficient and
+correct.
+
+Prior to Python 3.6, data loss could result when using bytes paths on Windows.
+With this change, using bytes to represent paths is now supported on Windows,
+provided those bytes are encoded with the encoding returned by
+:func:`sys.getfilesystemencoding()`, which now defaults to ``'utf-8'``.
+
+Applications that do not use str to represent paths should use
+:func:`os.fsencode()` and :func:`os.fsdecode()` to ensure their bytes are
+correctly encoded. To revert to the previous behaviour, set
+:envvar:`PYTHONLEGACYWINDOWSFSENCODING` or call
+:func:`sys._enablelegacywindowsfsencoding`.
+
+See :pep:`529` for more information and discussion of code modifications that
+may be required.
+
+
+.. _whatsnew36-pep528:
+
+PEP 528: Change Windows console encoding to UTF-8
+-------------------------------------------------
+
+The default console on Windows will now accept all Unicode characters and
+provide correctly read str objects to Python code. ``sys.stdin``,
+``sys.stdout`` and ``sys.stderr`` now default to utf-8 encoding.
+
+This change only applies when using an interactive console, and not when
+redirecting files or pipes. To revert to the previous behaviour for interactive
+console use, set :envvar:`PYTHONLEGACYWINDOWSIOENCODING`.
+
+.. seealso::
+
+ :pep:`528` -- Change Windows console encoding to UTF-8
+ PEP written and implemented by Steve Dower.
+
+
+.. _whatsnew36-pep520:
+
+PEP 520: Preserving Class Attribute Definition Order
+----------------------------------------------------
+
+Attributes in a class definition body have a natural ordering: the same
+order in which the names appear in the source. This order is now
+preserved in the new class's :attr:`~object.__dict__` attribute.
+
+Also, the effective default class *execution* namespace (returned from
+:ref:`type.__prepare__() <prepare>`) is now an insertion-order-preserving
+mapping.
+
+.. seealso::
+
+ :pep:`520` -- Preserving Class Attribute Definition Order
+ PEP written and implemented by Eric Snow.
+
+
+.. _whatsnew36-pep468:
+
+PEP 468: Preserving Keyword Argument Order
+------------------------------------------
+
+``**kwargs`` in a function signature is now guaranteed to be an
+insertion-order-preserving mapping.
+
+.. seealso::
+
+ :pep:`468` -- Preserving Keyword Argument Order
+ PEP written and implemented by Eric Snow.
+
+
+.. _whatsnew36-compactdict:
+
+New :ref:`dict <typesmapping>` implementation
+---------------------------------------------
+
+The :ref:`dict <typesmapping>` type now uses a "compact" representation
+`pioneered by PyPy <https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html>`_.
+The memory usage of the new :func:`dict` is between 20% and 25% smaller
+compared to Python 3.5.
+
+The order-preserving aspect of this new implementation is considered an
+implementation detail and should not be relied upon (this may change in
+the future, but it is desired to have this new dict implementation in
+the language for a few releases before changing the language spec to mandate
+order-preserving semantics for all current and future Python
+implementations; this also helps preserve backwards-compatibility
+with older versions of the language where random iteration order is
+still in effect, e.g. Python 3.5).
+
+(Contributed by INADA Naoki in :issue:`27350`. Idea
+`originally suggested by Raymond Hettinger
+<https://mail.python.org/pipermail/python-dev/2012-December/123028.html>`_.)
+
+
+.. _whatsnew36-pep523:
+
+PEP 523: Adding a frame evaluation API to CPython
+-------------------------------------------------
+
+While Python provides extensive support to customize how code
+executes, one place it has not done so is in the evaluation of frame
+objects. If you wanted some way to intercept frame evaluation in
+Python there really wasn't any way without directly manipulating
+function pointers for defined functions.
+
+:pep:`523` changes this by providing an API to make frame
+evaluation pluggable at the C level. This will allow for tools such
+as debuggers and JITs to intercept frame evaluation before the
+execution of Python code begins. This enables the use of alternative
+evaluation implementations for Python code, tracking frame
+evaluation, etc.
+
+This API is not part of the limited C API and is marked as private to
+signal that usage of this API is expected to be limited and only
+applicable to very select, low-level use-cases. Semantics of the
+API will change with Python as necessary.
+
+.. seealso::
+
+ :pep:`523` -- Adding a frame evaluation API to CPython
+ PEP written by Brett Cannon and Dino Viehland.
+
+
+.. _whatsnew36-pythonmalloc:
+
+PYTHONMALLOC environment variable
+---------------------------------
+
+The new :envvar:`PYTHONMALLOC` environment variable allows setting the Python
+memory allocators and/or install debug hooks.
+
+It is now possible to install debug hooks on Python memory allocators on Python
+compiled in release mode using ``PYTHONMALLOC=debug``. Effects of debug hooks:
+
+* Newly allocated memory is filled with the byte ``0xCB``
+* Freed memory is filled with the byte ``0xDB``
+* Detect violations of Python memory allocator API. For example,
+ :c:func:`PyObject_Free` called on a memory block allocated by
+ :c:func:`PyMem_Malloc`.
+* Detect write before the start of the buffer (buffer underflow)
+* Detect write after the end of the buffer (buffer overflow)
+* Check that the :term:`GIL <global interpreter lock>` is held when allocator
+ functions of :c:data:`PYMEM_DOMAIN_OBJ` (ex: :c:func:`PyObject_Malloc`) and
+ :c:data:`PYMEM_DOMAIN_MEM` (ex: :c:func:`PyMem_Malloc`) domains are called.
+
+Checking if the GIL is held is also a new feature of Python 3.6.
+
+See the :c:func:`PyMem_SetupDebugHooks` function for debug hooks on Python
+memory allocators.
+
+It is now also possible to force the usage of the :c:func:`malloc` allocator of
+the C library for all Python memory allocations using ``PYTHONMALLOC=malloc``.
+It helps to use external memory debuggers like Valgrind on a Python compiled in
+release mode.
+
+On error, the debug hooks on Python memory allocators now use the
+:mod:`tracemalloc` module to get the traceback where a memory block was
+allocated.
+
+Example of fatal error on buffer overflow using
+``python3.6 -X tracemalloc=5`` (store 5 frames in traces)::
+
+ Debug memory block at address p=0x7fbcd41666f8: API 'o'
+ 4 bytes originally requested
+ The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
+ The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
+ at tail+0: 0x02 *** OUCH
+ at tail+1: 0xfb
+ at tail+2: 0xfb
+ at tail+3: 0xfb
+ at tail+4: 0xfb
+ at tail+5: 0xfb
+ at tail+6: 0xfb
+ at tail+7: 0xfb
+ The block was made by call #1233329 to debug malloc/realloc.
+ Data at p: 1a 2b 30 00
+
+ Memory block allocated at (most recent call first):
+ File "test/test_bytes.py", line 323
+ File "unittest/case.py", line 600
+ File "unittest/case.py", line 648
+ File "unittest/suite.py", line 122
+ File "unittest/suite.py", line 84
+
+ Fatal Python error: bad trailing pad byte
+
+ Current thread 0x00007fbcdbd32700 (most recent call first):
+ File "test/test_bytes.py", line 323 in test_hex
+ File "unittest/case.py", line 600 in run
+ File "unittest/case.py", line 648 in __call__
+ File "unittest/suite.py", line 122 in run
+ File "unittest/suite.py", line 84 in __call__
+ File "unittest/suite.py", line 122 in run
+ File "unittest/suite.py", line 84 in __call__
+ ...
+
+(Contributed by Victor Stinner in :issue:`26516` and :issue:`26564`.)
+
+
+.. _whatsnew36-tracing:
+
+DTrace and SystemTap probing support
+------------------------------------
+
+Python can now be built ``--with-dtrace`` which enables static markers
+for the following events in the interpreter:
+
+* function call/return
+
+* garbage collection started/finished
+
+* line of code executed.
+
+This can be used to instrument running interpreters in production,
+without the need to recompile specific debug builds or providing
+application-specific profiling/debugging code.
+
+More details in :ref:`instrumentation`.
+
+The current implementation is tested on Linux and macOS. Additional
+markers may be added in the future.
+
+(Contributed by Łukasz Langa in :issue:`21590`, based on patches by
+Jesús Cea Avión, David Malcolm, and Nikhil Benesch.)
+
+
+Other Language Changes
+======================
+
+Some smaller changes made to the core Python language are:
+
+* A ``global`` or ``nonlocal`` statement must now textually appear
+ before the first use of the affected name in the same scope.
+ Previously this was a ``SyntaxWarning``.
+
+* It is now possible to set a :ref:`special method <specialnames>` to
+ ``None`` to indicate that the corresponding operation is not available.
+ For example, if a class sets :meth:`__iter__` to ``None``, the class
+ is not iterable.
+ (Contributed by Andrew Barnert and Ivan Levkivskyi in :issue:`25958`.)
+
+* Long sequences of repeated traceback lines are now abbreviated as
+ ``"[Previous line repeated {count} more times]"`` (see
+ :ref:`whatsnew36-traceback` for an example).
+ (Contributed by Emanuel Barry in :issue:`26823`.)
+
+* Import now raises the new exception :exc:`ModuleNotFoundError`
+ (subclass of :exc:`ImportError`) when it cannot find a module. Code
+ that current checks for ImportError (in try-except) will still work.
+ (Contributed by Eric Snow in :issue:`15767`.)
+
+* Class methods relying on zero-argument ``super()`` will now work correctly
+ when called from metaclass methods during class creation.
+ (Contributed by Martin Teichmann in :issue:`23722`.)
+
+
+New Modules
+===========
+
+.. _whatsnew36-pep506:
+
+secrets
+-------
+
+The main purpose of the new :mod:`secrets` module is to provide an obvious way
+to reliably generate cryptographically strong pseudo-random values suitable
+for managing secrets, such as account authentication, tokens, and similar.
+
+.. warning::
+
+ Note that the pseudo-random generators in the :mod:`random` module
+ should *NOT* be used for security purposes. Use :mod:`secrets`
+ on Python 3.6+ and :func:`os.urandom()` on Python 3.5 and earlier.
+
+.. seealso::
+
+ :pep:`506` -- Adding A Secrets Module To The Standard Library
+ PEP written and implemented by Steven D'Aprano.
+
+
+Improved Modules
+================
+
+array
+-----
+
+Exhausted iterators of :class:`array.array` will now stay exhausted even
+if the iterated array is extended. This is consistent with the behavior
+of other mutable sequences.
+
+Contributed by Serhiy Storchaka in :issue:`26492`.
+
+ast
+---
+
+The new :class:`ast.Constant` AST node has been added. It can be used
+by external AST optimizers for the purposes of constant folding.
+
+Contributed by Victor Stinner in :issue:`26146`.
+
+
+asyncio
+-------
+
+Starting with Python 3.6 the ``asyncio`` is no longer provisional and its
+API is considered stable.
+
+Notable changes in the :mod:`asyncio` module since Python 3.5.0
+(all backported to 3.5.x due to the provisional status):
+
+* The :func:`~asyncio.get_event_loop` function has been changed to
+ always return the currently running loop when called from couroutines
+ and callbacks.
+ (Contributed by Yury Selivanov in :issue:`28613`.)
+
+* The :func:`~asyncio.ensure_future` function and all functions that
+ use it, such as :meth:`loop.run_until_complete() <asyncio.BaseEventLoop.run_until_complete>`,
+ now accept all kinds of :term:`awaitable objects <awaitable>`.
+ (Contributed by Yury Selivanov.)
+
+* New :func:`~asyncio.run_coroutine_threadsafe` function to submit
+ coroutines to event loops from other threads.
+ (Contributed by Vincent Michel.)
+
+* New :meth:`Transport.is_closing() <asyncio.BaseTransport.is_closing>`
+ method to check if the transport is closing or closed.
+ (Contributed by Yury Selivanov.)
+
+* The :meth:`loop.create_server() <asyncio.BaseEventLoop.create_server>`
+ method can now accept a list of hosts.
+ (Contributed by Yann Sionneau.)
+
+* New :meth:`loop.create_future() <asyncio.BaseEventLoop.create_future>`
+ method to create Future objects. This allows alternative event
+ loop implementations, such as
+ `uvloop <https://github.com/MagicStack/uvloop>`_, to provide a faster
+ :class:`asyncio.Future` implementation.
+ (Contributed by Yury Selivanov in :issue:`27041`.)
+
+* New :meth:`loop.get_exception_handler() <asyncio.BaseEventLoop.get_exception_handler>`
+ method to get the current exception handler.
+ (Contributed by Yury Selivanov in :issue:`27040`.)
+
+* New :meth:`StreamReader.readuntil() <asyncio.StreamReader.readuntil>`
+ method to read data from the stream until a separator bytes
+ sequence appears.
+ (Contributed by Mark Korenberg.)
+
+* The performance of :meth:`StreamReader.readexactly() <asyncio.StreamReader.readexactly>`
+ has been improved.
+ (Contributed by Mark Korenberg in :issue:`28370`.)
+
+* The :meth:`loop.getaddrinfo() <asyncio.BaseEventLoop.getaddrinfo>`
+ method is optimized to avoid calling the system ``getaddrinfo``
+ function if the address is already resolved.
+ (Contributed by A. Jesse Jiryu Davis.)
+
+* The :meth:`BaseEventLoop.stop() <asyncio.BaseEventLoop.stop>`
+ method has been changed to stop the loop immediately after
+ the current iteration. Any new callbacks scheduled as a result
+ of the last iteration will be discarded.
+ (Contributed by Guido van Rossum in :issue:`25593`.)
+
+* :meth:`Future.set_exception <asyncio.futures.Future.set_exception>`
+ will now raise :exc:`TypeError` when passed an instance of
+ :exc:`StopIteration` exception.
+ (Contributed by Chris Angelico in :issue:`26221`.)
+
+* New :meth:`Loop.connect_accepted_socket() <asyncio.BaseEventLoop.connect_accepted_socket>`
+ method to be used by servers that accept connections outside of asyncio,
+ but that use asyncio to handle them.
+ (Contributed by Jim Fulton in :issue:`27392`.)
+
+
+binascii
+--------
+
+The :func:`~binascii.b2a_base64` function now accepts an optional *newline*
+keyword argument to control whether the newline character is appended to the
+return value.
+(Contributed by Victor Stinner in :issue:`25357`.)
+
+
+cmath
+-----
+
+The new :const:`cmath.tau` (τ) constant has been added.
+(Contributed by Lisa Roach in :issue:`12345`, see :pep:`628` for details.)
+
+New constants: :const:`cmath.inf` and :const:`cmath.nan` to
+match :const:`math.inf` and :const:`math.nan`, and also :const:`cmath.infj`
+and :const:`cmath.nanj` to match the format used by complex repr.
+(Contributed by Mark Dickinson in :issue:`23229`.)
+
+
+collections
+-----------
+
+The new :class:`~collections.abc.Collection` abstract base class has been
+added to represent sized iterable container classes.
+(Contributed by Ivan Levkivskyi, docs by Neil Girdhar in :issue:`27598`.)
+
+The new :class:`~collections.abc.Reversible` abstract base class represents
+iterable classes that also provide the :meth:`__reversed__`.
+(Contributed by Ivan Levkivskyi in :issue:`25987`.)
+
+The new :class:`~collections.abc.AsyncGenerator` abstract base class represents
+asynchronous generators.
+(Contributed by Yury Selivanov in :issue:`28720`.)
+
+The :func:`~collections.namedtuple` function now accepts an optional
+keyword argument *module*, which, when specified, is used for
+the ``__module__`` attribute of the returned named tuple class.
+(Contributed by Raymond Hettinger in :issue:`17941`.)
+
+The *verbose* and *rename* arguments for
+:func:`~collections.namedtuple` are now keyword-only.
+(Contributed by Raymond Hettinger in :issue:`25628`.)
+
+Recursive :class:`collections.deque` instances can now be pickled.
+(Contributed by Serhiy Storchaka in :issue:`26482`.)
+
+
+concurrent.futures
+------------------
+
+The :class:`ThreadPoolExecutor <concurrent.futures.thread.ThreadPoolExecutor`
+class constructor now accepts an optional *thread_name_prefix* argument
+to make it possible to customize the names of the threads created by the
+pool.
+(Contributed by Gregory P. Smith in :issue:`27664`.)
+
+
+contextlib
+----------
+
+The :class:`contextlib.AbstractContextManager` class has been added to
+provide an abstract base class for context managers. It provides a
+sensible default implementation for `__enter__()` which returns
+``self`` and leaves `__exit__()` an abstract method. A matching
+class has been added to the :mod:`typing` module as
+:class:`typing.ContextManager`.
+(Contributed by Brett Cannon in :issue:`25609`.)
+
+
+datetime
+--------
+
+The :class:`~datetime.datetime` and :class:`~datetime.time` classes have
+the new :attr:`~time.fold` attribute used to disambiguate local time
+when necessary. Many functions in the :mod:`datetime` have been
+updated to support local time disambiguation.
+See :ref:`Local Time Disambiguation <whatsnew36-pep495>` section for more
+information.
+(Contributed by Alexander Belopolsky in :issue:`24773`.)
+
+The :meth:`datetime.strftime() <datetime.datetime.strftime>` and
+:meth:`date.strftime() <datetime.date.strftime>` methods now support
+ISO 8601 date directives ``%G``, ``%u`` and ``%V``.
+(Contributed by Ashley Anderson in :issue:`12006`.)
+
+The :func:`datetime.isoformat() <datetime.datetime.isoformat>` function
+now accepts an optional *timespec* argument that specifies the number
+of additional components of the time value to include.
+(Contributed by Alessandro Cucci and Alexander Belopolsky in :issue:`19475`.)
+
+The :meth:`datetime.combine() <datetime.datetime.combine>` now
+accepts an optional *tzinfo* argument.
+(Contributed by Alexander Belopolsky in :issue:`27661`.)
+
+
+decimal
+-------
+
+New :meth:`Decimal.as_integer_ratio() <decimal.Decimal.as_integer_ratio>`
+method that returns a pair ``(n, d)`` of integers that represent the given
+:class:`~decimal.Decimal` instance as a fraction, in lowest terms and
+with a positive denominator::
+
+ >>> Decimal('-3.14').as_integer_ratio()
+ (-157, 50)
+
+(Contributed by Stefan Krah amd Mark Dickinson in :issue:`25928`.)
+
+
+
+distutils
+---------
+
+The ``default_format`` attribute has been removed from
+:class:`distutils.command.sdist.sdist` and the ``formats``
+attribute defaults to ``['gztar']``. Although not anticipated,
+Any code relying on the presence of ``default_format`` may
+need to be adapted. See :issue:`27819` for more details.
+
+
+email
+-----
+
+The new email API, enabled via the *policy* keyword to various constructors, is
+no longer provisional. The :mod:`email` documentation has been reorganized and
+rewritten to focus on the new API, while retaining the old documentation for
+the legacy API. (Contributed by R. David Murray in :issue:`24277`.)
+
+The :mod:`email.mime` classes now all accept an optional *policy* keyword.
+(Contributed by Berker Peksag in :issue:`27331`.)
+
+The :class:`~email.generator.DecodedGenerator` now supports the *policy*
+keyword.
+
+There is a new :mod:`~email.policy` attribute,
+:attr:`~email.policy.Policy.message_factory`, that controls what class is used
+by default when the parser creates new message objects. For the
+:attr:`email.policy.compat32` policy this is :class:`~email.message.Message`,
+for the new policies it is :class:`~email.message.EmailMessage`.
+(Contributed by R. David Murray in :issue:`20476`.)
+
+
+encodings
+---------
+
+On Windows, added the ``'oem'`` encoding to use ``CP_OEMCP`` and the ``'ansi'``
+alias for the existing ``'mbcs'`` encoding, which uses the ``CP_ACP`` code page.
+(Contributed by Steve Dower in :issue:`27959`.)
+
+
+enum
+----
+
+Two new enumeration base classes have been added to the :mod:`enum` module:
+:class:`~enum.Flag` and :class:`~enum.IntFlags`. Both are used to define
+constants that can be combined using the bitwise operators.
+(Contributed by Ethan Furman in :issue:`23591`.)
+
+Many standard library modules have been updated to use the
+:class:`~enum.IntFlags` class for their constants.
+
+The new :class:`enum.auto` value can be used to assign values to enum
+members automatically::
+
+ >>> from enum import Enum, auto
+ >>> class Color(Enum):
+ ... red = auto()
+ ... blue = auto()
+ ... green = auto()
+ ...
+ >>> list(Color)
+ [<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>]
+
+
+faulthandler
+------------
+
+On Windows, the :mod:`faulthandler` module now installs a handler for Windows
+exceptions: see :func:`faulthandler.enable`. (Contributed by Victor Stinner in
+:issue:`23848`.)
+
+
+fileinput
+---------
+
+:func:`~fileinput.hook_encoded` now supports the *errors* argument.
+(Contributed by Joseph Hackman in :issue:`25788`.)
+
+
+hashlib
+-------
+
+:mod:`hashlib` supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.
+(Contributed by Christian Heimes in :issue:`26470`.)
+
+BLAKE2 hash functions were added to the module. :func:`~hashlib.blake2b`
+and :func:`~hashlib.blake2s` are always available and support the full
+feature set of BLAKE2.
+(Contributed by Christian Heimes in :issue:`26798` based on code by
+Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.)
+
+The SHA-3 hash functions :func:`~hashlib.sha3_224`, :func:`~hashlib.sha3_256`,
+:func:`~hashlib.sha3_384`, :func:`~hashlib.sha3_512`, and SHAKE hash functions
+:func:`~hashlib.shake_128` and :func:`~hashlib.shake_256` were added.
+(Contributed by Christian Heimes in :issue:`16113`. Keccak Code Package
+by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and
+Ronny Van Keer.)
+
+The password-based key derivation function :func:`~hashlib.scrypt` is now
+available with OpenSSL 1.1.0 and newer.
+(Contributed by Christian Heimes in :issue:`27928`.)
+
+http.client
+-----------
+
+:meth:`HTTPConnection.request() <http.client.HTTPConnection.request>` and
+:meth:`~http.client.HTTPConnection.endheaders` both now support
+chunked encoding request bodies.
+(Contributed by Demian Brecht and Rolf Krahl in :issue:`12319`.)
+
+
+idlelib and IDLE
+----------------
+
+The idlelib package is being modernized and refactored to make IDLE look and
+work better and to make the code easier to understand, test, and improve. Part
+of making IDLE look better, especially on Linux and Mac, is using ttk widgets,
+mostly in the dialogs. As a result, IDLE no longer runs with tcl/tk 8.4. It
+now requires tcl/tk 8.5 or 8.6. We recommend running the latest release of
+either.
+
+'Modernizing' includes renaming and consolidation of idlelib modules. The
+renaming of files with partial uppercase names is similar to the renaming of,
+for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0. As a
+result, imports of idlelib files that worked in 3.5 will usually not work in
+3.6. At least a module name change will be needed (see idlelib/README.txt),
+sometimes more. (Name changes contributed by Al Swiegart and Terry Reedy in
+:issue:`24225`. Most idlelib patches since have been and will be part of the
+process.)
+
+In compensation, the eventual result with be that some idlelib classes will be
+easier to use, with better APIs and docstrings explaining them. Additional
+useful information will be added to idlelib when available.
+
+
+importlib
+---------
+
+Import now raises the new exception :exc:`ModuleNotFoundError`
+(subclass of :exc:`ImportError`) when it cannot find a module. Code
+that current checks for ``ImportError`` (in try-except) will still work.
+(Contributed by Eric Snow in :issue:`15767`.)
+
+:class:`importlib.util.LazyLoader` now calls
+:meth:`~importlib.abc.Loader.create_module` on the wrapped loader, removing the
+restriction that :class:`importlib.machinery.BuiltinImporter` and
+:class:`importlib.machinery.ExtensionFileLoader` couldn't be used with
+:class:`importlib.util.LazyLoader`.
+
+:func:`importlib.util.cache_from_source`,
+:func:`importlib.util.source_from_cache`, and
+:func:`importlib.util.spec_from_file_location` now accept a
+:term:`path-like object`.
+
+
+inspect
+-------
+
+The :func:`inspect.signature() <inspect.signature>` function now reports the
+implicit ``.0`` parameters generated by the compiler for comprehension and
+generator expression scopes as if they were positional-only parameters called
+``implicit0``. (Contributed by Jelle Zijlstra in :issue:`19611`.)
+
+
+json
+----
+
+:func:`json.load` and :func:`json.loads` now support binary input. Encoded
+JSON should be represented using either UTF-8, UTF-16, or UTF-32.
+(Contributed by Serhiy Storchaka in :issue:`17909`.)
+
+
+logging
+-------
+
+The new :meth:`WatchedFileHandler.reopenIfNeeded() <logging.handlers.WatchedFileHandler.reopenIfNeeded>`
+method has been added to add the ability to check if the log file needs to
+be reopened.
+(Contributed by Marian Horban in :issue:`24884`.)
+
+
+math
+----
+
+The tau (τ) constant has been added to the :mod:`math` and :mod:`cmath`
+modules.
+(Contributed by Lisa Roach in :issue:`12345`, see :pep:`628` for details.)
+
+
+multiprocessing
+---------------
+
+:ref:`Proxy Objects <multiprocessing-proxy_objects>` returned by
+:func:`multiprocessing.Manager` can now be nested.
+(Contributed by Davin Potts in :issue:`6766`.)
+
+
+os
+--
+
+See the summary for :ref:`PEP 519 <whatsnew36-pep519>` for details on how the
+:mod:`os` and :mod:`os.path` modules now support
+:term:`path-like objects <path-like object>`.
+
+:func:`~os.scandir` now supports :class:`bytes` paths on Windows.
+
+A new :meth:`~os.scandir.close` method allows explicitly closing a
+:func:`~os.scandir` iterator. The :func:`~os.scandir` iterator now
+supports the :term:`context manager` protocol. If a :func:`scandir`
+iterator is neither exhausted nor explicitly closed a :exc:`ResourceWarning`
+will be emitted in its destructor.
+(Contributed by Serhiy Storchaka in :issue:`25994`.)
+
+On Linux, :func:`os.urandom` now blocks until the system urandom entropy pool
+is initialized to increase the security. See the :pep:`524` for the rationale.
+
+The Linux ``getrandom()`` syscall (get random bytes) is now exposed as the new
+:func:`os.getrandom` function.
+(Contributed by Victor Stinner, part of the :pep:`524`)
+
+
+pathlib
+-------
+
+:mod:`pathlib` now supports :term:`path-like objects <path-like object>`.
+(Contributed by Brett Cannon in :issue:`27186`.)
+
+See the summary for :ref:`PEP 519 <whatsnew36-pep519>` for details.
+
+
+pdb
+---
+
+The :class:`~pdb.Pdb` class constructor has a new optional *readrc* argument
+to control whether ``.pdbrc`` files should be read.
+
+
+pickle
+------
+
+Objects that need calling ``__new__`` with keyword arguments can now be pickled
+using :ref:`pickle protocols <pickle-protocols>` older than protocol version 4.
+Protocol version 4 already supports this case. (Contributed by Serhiy
+Storchaka in :issue:`24164`.)
+
+
+pickletools
+-----------
+
+:func:`pickletools.dis()` now outputs implicit memo index for the
+``MEMOIZE`` opcode.
+(Contributed by Serhiy Storchaka in :issue:`25382`.)
+
+
+pydoc
+-----
+
+The :mod:`pydoc` module has learned to respect the ``MANPAGER``
+environment variable.
+(Contributed by Matthias Klose in :issue:`8637`.)
+
+:func:`help` and :mod:`pydoc` can now list named tuple fields in the
+order they were defined rather than alphabetically.
+(Contributed by Raymond Hettinger in :issue:`24879`.)
+
+
+random
+-------
+
+The new :func:`~random.choices` function returns a list of elements of
+specified size from the given population with optional weights.
+(Contributed by Raymond Hettinger in :issue:`18844`.)
+
+
+re
+--
+
+Added support of modifier spans in regular expressions. Examples:
+``'(?i:p)ython'`` matches ``'python'`` and ``'Python'``, but not ``'PYTHON'``;
+``'(?i)g(?-i:v)r'`` matches ``'GvR'`` and ``'gvr'``, but not ``'GVR'``.
+(Contributed by Serhiy Storchaka in :issue:`433028`.)
+
+Match object groups can be accessed by ``__getitem__``, which is
+equivalent to ``group()``. So ``mo['name']`` is now equivalent to
+``mo.group('name')``. (Contributed by Eric Smith in :issue:`24454`.)
+
+:class:`~re.Match` objects in the now support
+:meth:`index-like objects <object.__index__>` as group
+indices.
+(Contributed by Jeroen Demeyer and Xiang Zhang in :issue:`27177`.)
+
+
+readline
+--------
+
+Added :func:`~readline.set_auto_history` to enable or disable
+automatic addition of input to the history list. (Contributed by
+Tyler Crompton in :issue:`26870`.)
+
+
+rlcompleter
+-----------
+
+Private and special attribute names now are omitted unless the prefix starts
+with underscores. A space or a colon is added after some completed keywords.
+(Contributed by Serhiy Storchaka in :issue:`25011` and :issue:`25209`.)
+
+
+shlex
+-----
+
+The :class:`~shlex.shlex` has much
+:ref:`improved shell compatibility <improved-shell-compatibility>`
+through the new *punctuation_chars* argument to control which characters
+are treated as punctuation.
+(Contributed by Vinay Sajip in :issue:`1521950`.)
+
+
+site
+----
+
+When specifying paths to add to :attr:`sys.path` in a `.pth` file,
+you may now specify file paths on top of directories (e.g. zip files).
+(Contributed by Wolfgang Langner in :issue:`26587`).
+
+
+sqlite3
+-------
+
+:attr:`sqlite3.Cursor.lastrowid` now supports the ``REPLACE`` statement.
+(Contributed by Alex LordThorsen in :issue:`16864`.)
+
+
+socket
+------
+
+The :func:`~socket.socket.ioctl` function now supports the
+:data:`~socket.SIO_LOOPBACK_FAST_PATH` control code.
+(Contributed by Daniel Stokes in :issue:`26536`.)
+
+The :meth:`~socket.socket.getsockopt` constants ``SO_DOMAIN``,
+``SO_PROTOCOL``, ``SO_PEERSEC``, and ``SO_PASSSEC`` are now supported.
+(Contributed by Christian Heimes in :issue:`26907`.)
+
+The :meth:`~socket.socket.setsockopt` now supports the
+``setsockopt(level, optname, None, optlen: int)`` form.
+(Contributed by Christian Heimes in issue:`27744`.)
+
+The socket module now supports the address family
+:data:`~socket.AF_ALG` to interface with Linux Kernel crypto API. ``ALG_*``,
+``SOL_ALG`` and :meth:`~socket.socket.sendmsg_afalg` were added.
+(Contributed by Christian Heimes in :issue:`27744` with support from
+Victor Stinner.)
+
+
+socketserver
+------------
+
+Servers based on the :mod:`socketserver` module, including those
+defined in :mod:`http.server`, :mod:`xmlrpc.server` and
+:mod:`wsgiref.simple_server`, now support the :term:`context manager`
+protocol.
+(Contributed by Aviv Palivoda in :issue:`26404`.)
+
+The :attr:`~socketserver.StreamRequestHandler.wfile` attribute of
+:class:`~socketserver.StreamRequestHandler` classes now implements
+the :class:`io.BufferedIOBase` writable interface. In particular,
+calling :meth:`~io.BufferedIOBase.write` is now guaranteed to send the
+data in full. (Contributed by Martin Panter in :issue:`26721`.)
+
+
+ssl
+---
+
+:mod:`ssl` supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.
+(Contributed by Christian Heimes in :issue:`26470`.)
+
+3DES has been removed from the default cipher suites and ChaCha20 Poly1305
+cipher suites have been added.
+(Contributed by Christian Heimes in :issue:`27850` and :issue:`27766`.)
+
+:class:`~ssl.SSLContext` has better default configuration for options
+and ciphers.
+(Contributed by Christian Heimes in :issue:`28043`.)
+
+SSL session can be copied from one client-side connection to another
+with the new :class:`~ssl.SSLSession` class. TLS session resumption can
+speed up the initial handshake, reduce latency and improve performance
+(Contributed by Christian Heimes in :issue:`19500` based on a draft by
+Alex Warhawk.)
+
+The new :meth:`~ssl.SSLContext.get_ciphers` method can be used to
+get a list of enabled ciphers in order of cipher priority.
+
+All constants and flags have been converted to :class:`~enum.IntEnum` and
+:class:`~enum.IntFlags`.
+(Contributed by Christian Heimes in :issue:`28025`.)
+
+Server and client-side specific TLS protocols for :class:`~ssl.SSLContext`
+were added.
+(Contributed by Christian Heimes in :issue:`28085`.)
+
+
+statistics
+----------
+
+A new :func:`~statistics.harmonic_mean` function has been added.
+(Contributed by Steven D'Aprano in :issue:`27181`.)
+
+
+struct
+------
+
+:mod:`struct` now supports IEEE 754 half-precision floats via the ``'e'``
+format specifier.
+(Contributed by Eli Stevens, Mark Dickinson in :issue:`11734`.)
+
+
+subprocess
+----------
+
+:class:`subprocess.Popen` destructor now emits a :exc:`ResourceWarning` warning
+if the child process is still running. Use the context manager protocol (``with
+proc: ...``) or call explicitly the :meth:`~subprocess.Popen.wait` method to
+read the exit status of the child process (Contributed by Victor Stinner in
+:issue:`26741`).
+
+The :class:`subprocess.Popen` constructor and all functions that pass arguments
+through to it now accept *encoding* and *errors* arguments. Specifying either
+of these will enable text mode for the *stdin*, *stdout* and *stderr* streams.
+(Contributed by Steve Dower in :issue:`6135`.)
+
+
+sys
+---
+
+The new :func:`~sys.getfilesystemencodeerrors` function returns the name of
+the error mode used to convert between Unicode filenames and bytes filenames.
+(Contributed by Steve Dower in :issue:`27781`.)
+
+On Windows the return value of the :func:`~sys.getwindowsversion` function
+now includes the *platform_version* field which contains the accurate major
+version, minor version and build number of the current operating system,
+rather than the version that is being emulated for the process
+(Contributed by Steve Dower in :issue:`27932`.)
+
+
+telnetlib
+---------
+
+:class:`~telnetlib.Telnet` is now a context manager (contributed by
+Stéphane Wirtel in :issue:`25485`).
+
+
+time
+----
+
+The :class:`~time.struct_time` attributes :attr:`tm_gmtoff` and
+:attr:`tm_zone` are now available on all platforms.
+
+
+timeit
+------
+
+The new :meth:`Timer.autorange() <timeit.Timer.autorange>` convenience
+method has been added to call :meth:`Timer.timeit() <timeit.Timer.timeit>`
+repeatedly so that the total run time is greater or equal to 200 milliseconds.
+(Contributed by Steven D'Aprano in :issue:`6422`.)
+
+:mod:`timeit` now warns when there is substantial (4x) variance
+between best and worst times.
+(Contributed by Serhiy Storchaka in :issue:`23552`.)
+
+
+tkinter
+-------
+
+Added methods :meth:`~tkinter.Variable.trace_add`,
+:meth:`~tkinter.Variable.trace_remove` and :meth:`~tkinter.Variable.trace_info`
+in the :class:`tkinter.Variable` class. They replace old methods
+:meth:`~tkinter.Variable.trace_variable`, :meth:`~tkinter.Variable.trace`,
+:meth:`~tkinter.Variable.trace_vdelete` and
+:meth:`~tkinter.Variable.trace_vinfo` that use obsolete Tcl commands and might
+not work in future versions of Tcl.
+(Contributed by Serhiy Storchaka in :issue:`22115`).
+
+
+.. _whatsnew36-traceback:
+
+traceback
+---------
+
+Both the traceback module and the interpreter's builtin exception display now
+abbreviate long sequences of repeated lines in tracebacks as shown in the
+following example::
+
+ >>> def f(): f()
+ ...
+ >>> f()
+ Traceback (most recent call last):
+ File "<stdin>", line 1, in <module>
+ File "<stdin>", line 1, in f
+ File "<stdin>", line 1, in f
+ File "<stdin>", line 1, in f
+ [Previous line repeated 995 more times]
+ RecursionError: maximum recursion depth exceeded
+
+(Contributed by Emanuel Barry in :issue:`26823`.)
+
+
+tracemalloc
+-----------
+
+The :mod:`tracemalloc` module now supports tracing memory allocations in
+multiple different address spaces.
+
+The new :class:`~tracemalloc.DomainFilter` filter class has been added
+to filter block traces by their address space (domain).
+
+(Contributed by Victor Stinner in :issue:`26588`.)
+
+
+.. _whatsnew36-typing:
+
+typing
+------
+
+Starting with Python 3.6 the :mod:`typing` module is no longer provisional
+and its API is considered stable.
+
+Since the :mod:`typing` module was :term:`provisional <provisional api>`
+in Python 3.5, all changes introduced in Python 3.6 have also been
+backported to Python 3.5.x.
+
+The :mod:`typing` module has a much improved support for generic type
+aliases. For example ``Dict[str, Tuple[S, T]]`` is now a valid
+type annotation.
+(Contributed by Guido van Rossum in `Github #195
+<https://github.com/python/typing/pull/195>`_.)
+
+The :class:`typing.ContextManager` class has been added for
+representing :class:`contextlib.AbstractContextManager`.
+(Contributed by Brett Cannon in :issue:`25609`.)
+
+The :class:`typing.Collection` class has been added for
+representing :class:`collections.abc.Collection`.
+(Contributed by Ivan Levkivskyi in :issue:`27598`.)
+
+The :const:`typing.ClassVar` type construct has been added to
+mark class variables. As introduced in :pep:`526`, a variable annotation
+wrapped in ClassVar indicates that a given attribute is intended to be used as
+a class variable and should not be set on instances of that class.
+(Contributed by Ivan Levkivskyi in `Github #280
+<https://github.com/python/typing/issues/280>`_.)
+
+A new :const:`~typing.TYPE_CHECKING` constant that is assumed to be
+``True`` by the static type chekers, but is ``False`` at runtime.
+(Contributed by Guido van Rossum in `Github #230
+<https://github.com/python/typing/issues/230>`_.)
+
+A new :func:`~typing.NewType` helper function has been added to create
+lightweight distinct types for annotations::
+
+ from typing import NewType
+
+ UserId = NewType('UserId', int)
+ some_id = UserId(524313)
+
+The static type checker will treat the new type as if it were a subclass
+of the original type. (Contributed by Ivan Levkivskyi in `Github #189
+<https://github.com/python/typing/issues/189>`_.)
+
+
+unicodedata
+-----------
+
+The :mod:`unicodedata` module now uses data from `Unicode 9.0.0
+<http://unicode.org/versions/Unicode9.0.0/>`_.
+(Contributed by Benjamin Peterson.)
+
+
+unittest.mock
+-------------
+
+The :class:`~unittest.mock.Mock` class has the following improvements:
+
+* Two new methods, :meth:`Mock.assert_called()
+ <unittest.mock.Mock.assert_called>` and :meth:`Mock.assert_called_once()
+ <unittest.mock.Mock.assert_called_once>` to check if the mock object
+ was called.
+ (Contributed by Amit Saha in :issue:`26323`.)
+
+* The :meth:`Mock.reset_mock() <unittest.mock.Mock.reset_mock>` method
+ now has two optional keyword only arguments: *return_value* and
+ *side_effect*.
+ (Contributed by Kushal Das in :issue:`21271`.)
+
+
+urllib.request
+--------------
+
+If a HTTP request has a file or iterable body (other than a
+bytes object) but no ``Content-Length`` header, rather than
+throwing an error, :class:`~urllib.request.AbstractHTTPHandler` now
+falls back to use chunked transfer encoding.
+(Contributed by Demian Brecht and Rolf Krahl in :issue:`12319`.)
+
+
+urllib.robotparser
+------------------
+
+:class:`~urllib.robotparser.RobotFileParser` now supports the ``Crawl-delay`` and
+``Request-rate`` extensions.
+(Contributed by Nikolay Bogoychev in :issue:`16099`.)
+
+
+venv
+----
+
+:mod:`venv` accepts a new parameter ``--prompt``. This parameter provides an
+alternative prefix for the virtual environment. (Proposed by Łukasz Balcerzak
+and ported to 3.6 by Stéphane Wirtel in :issue:`22829`.)
+
+
+warnings
+--------
+
+A new optional *source* parameter has been added to the
+:func:`warnings.warn_explicit` function: the destroyed object which emitted a
+:exc:`ResourceWarning`. A *source* attribute has also been added to
+:class:`warnings.WarningMessage` (contributed by Victor Stinner in
+:issue:`26568` and :issue:`26567`).
+
+When a :exc:`ResourceWarning` warning is logged, the :mod:`tracemalloc` is now
+used to try to retrieve the traceback where the detroyed object was allocated.
+
+Example with the script ``example.py``::
+
+ import warnings
+
+ def func():
+ return open(__file__)
+
+ f = func()
+ f = None
+
+Output of the command ``python3.6 -Wd -X tracemalloc=5 example.py``::
+
+ example.py:7: ResourceWarning: unclosed file <_io.TextIOWrapper name='example.py' mode='r' encoding='UTF-8'>
+ f = None
+ Object allocated at (most recent call first):
+ File "example.py", lineno 4
+ return open(__file__)
+ File "example.py", lineno 6
+ f = func()
+
+The "Object allocated at" traceback is new and only displayed if
+:mod:`tracemalloc` is tracing Python memory allocations and if the
+:mod:`warnings` was already imported.
+
+
+winreg
+------
+
+Added the 64-bit integer type :data:`REG_QWORD <winreg.REG_QWORD>`.
+(Contributed by Clement Rouault in :issue:`23026`.)
+
+
+winsound
+--------
+
+Allowed keyword arguments to be passed to :func:`Beep <winsound.Beep>`,
+:func:`MessageBeep <winsound.MessageBeep>`, and :func:`PlaySound
+<winsound.PlaySound>` (:issue:`27982`).
+
+
+xmlrpc.client
+-------------
+
+The :mod:`xmlrpc.client` module now supports unmarshalling
+additional data types used by Apache XML-RPC implementation
+for numerics and ``None``.
+(Contributed by Serhiy Storchaka in :issue:`26885`.)
+
+
+zipfile
+-------
+
+A new :meth:`ZipInfo.from_file() <zipfile.ZipInfo.from_file>` class method
+allows making a :class:`~zipfile.ZipInfo` instance from a filesystem file.
+A new :meth:`ZipInfo.is_dir() <zipfile.ZipInfo.is_dir>` method can be used
+to check if the :class:`~zipfile.ZipInfo` instance represents a directory.
+(Contributed by Thomas Kluyver in :issue:`26039`.)
+
+The :meth:`ZipFile.open() <zipfile.ZipFile.open>` method can now be used to
+write data into a ZIP file, as well as for extracting data.
+(Contributed by Thomas Kluyver in :issue:`26039`.)
+
+
+zlib
+----
+
+The :func:`~zlib.compress` and :func:`~zlib.decompress` functions now accept
+keyword arguments.
+(Contributed by Aviv Palivoda in :issue:`26243` and
+Xiang Zhang in :issue:`16764` respectively.)
+
+
+Optimizations
+=============
+
+* Python interpreter now uses 16-bit wordcode instead of bytecode which
+ made a number of opcode optimizations possible.
+ (Contributed by Demur Rumed with input and reviews from
+ Serhiy Storchaka and Victor Stinner in :issue:`26647` and :issue:`28050`.)
+
+* The :class:`Future <asyncio.futures.Future>` now has an optimized
+ C implementation.
+ (Contributed by Yury Selivanov and INADA Naoki in :issue:`26801`.)
+
+* The :class:`Task <asyncio.tasks.Task>` now has an optimized
+ C implementation. (Contributed by Yury Selivanov in :issue:`28544`.)
+
+* Various implementation improvements in the :mod:`typing` module
+ (such as caching of generic types) allow up to 30 times performance
+ improvements and reduced memory footprint.
+
+* The ASCII decoder is now up to 60 times as fast for error handlers
+ ``surrogateescape``, ``ignore`` and ``replace`` (Contributed
+ by Victor Stinner in :issue:`24870`).
+
+* The ASCII and the Latin1 encoders are now up to 3 times as fast for the
+ error handler ``surrogateescape``
+ (Contributed by Victor Stinner in :issue:`25227`).
+
+* The UTF-8 encoder is now up to 75 times as fast for error handlers
+ ``ignore``, ``replace``, ``surrogateescape``, ``surrogatepass`` (Contributed
+ by Victor Stinner in :issue:`25267`).
+
+* The UTF-8 decoder is now up to 15 times as fast for error handlers
+ ``ignore``, ``replace`` and ``surrogateescape`` (Contributed
+ by Victor Stinner in :issue:`25301`).
+
+* ``bytes % args`` is now up to 2 times faster. (Contributed by Victor Stinner
+ in :issue:`25349`).
+
+* ``bytearray % args`` is now between 2.5 and 5 times faster. (Contributed by
+ Victor Stinner in :issue:`25399`).
+
+* Optimize :meth:`bytes.fromhex` and :meth:`bytearray.fromhex`: they are now
+ between 2x and 3.5x faster. (Contributed by Victor Stinner in :issue:`25401`).
+
+* Optimize ``bytes.replace(b'', b'.')`` and ``bytearray.replace(b'', b'.')``:
+ up to 80% faster. (Contributed by Josh Snider in :issue:`26574`).
+
+* Allocator functions of the :c:func:`PyMem_Malloc` domain
+ (:c:data:`PYMEM_DOMAIN_MEM`) now use the :ref:`pymalloc memory allocator
+ <pymalloc>` instead of :c:func:`malloc` function of the C library. The
+ pymalloc allocator is optimized for objects smaller or equal to 512 bytes
+ with a short lifetime, and use :c:func:`malloc` for larger memory blocks.
+ (Contributed by Victor Stinner in :issue:`26249`).
+
+* :func:`pickle.load` and :func:`pickle.loads` are now up to 10% faster when
+ deserializing many small objects (Contributed by Victor Stinner in
+ :issue:`27056`).
+
+- Passing :term:`keyword arguments <keyword argument>` to a function has an
+ overhead in comparison with passing :term:`positional arguments
+ <positional argument>`. Now in extension functions implemented with using
+ Argument Clinic this overhead is significantly decreased.
+ (Contributed by Serhiy Storchaka in :issue:`27574`).
+
+* Optimized :func:`~glob.glob` and :func:`~glob.iglob` functions in the
+ :mod:`glob` module; they are now about 3--6 times faster.
+ (Contributed by Serhiy Storchaka in :issue:`25596`).
+
+* Optimized globbing in :mod:`pathlib` by using :func:`os.scandir`;
+ it is now about 1.5--4 times faster.
+ (Contributed by Serhiy Storchaka in :issue:`26032`).
+
+* :class:`xml.etree.ElementTree` parsing, iteration and deepcopy performance
+ has been significantly improved.
+ (Contributed by Serhiy Storchaka in :issue:`25638`, :issue:`25873`,
+ and :issue:`25869`.)
+
+* Creation of :class:`fractions.Fraction` instances from floats and
+ decimals is now 2 to 3 times faster.
+ (Contributed by Serhiy Storchaka in :issue:`25971`.)
+
+
+Build and C API Changes
+=======================
+
+* Python now requires some C99 support in the toolchain to build.
+ Most notably, Python now uses standard integer types and macros in
+ place of custom macros like ``PY_LONG_LONG``.
+ For more information, see :pep:`7` and :issue:`17884`.
+
+* Cross-compiling CPython with the Android NDK and the Android API level set to
+ 21 (Android 5.0 Lollilop) or greater, runs successfully. While Android is not
+ yet a supported platform, the Python test suite runs on the Android emulator
+ with only about 16 tests failures. See the Android meta-issue :issue:`26865`.
+
++* The ``--enable-optimizations`` configure flag has been added. Turning it on
+ will activate expensive optimizations like PGO.
+ (Original patch by Alecsandru Patrascu of Intel in :issue:`26539`.)
+
+* The :term:`GIL <global interpreter lock>` must now be held when allocator
+ functions of :c:data:`PYMEM_DOMAIN_OBJ` (ex: :c:func:`PyObject_Malloc`) and
+ :c:data:`PYMEM_DOMAIN_MEM` (ex: :c:func:`PyMem_Malloc`) domains are called.
+
+* New :c:func:`Py_FinalizeEx` API which indicates if flushing buffered data
+ failed.
+ (Contributed by Martin Panter in :issue:`5319`.)
+
+* :c:func:`PyArg_ParseTupleAndKeywords` now supports :ref:`positional-only
+ parameters <positional-only_parameter>`. Positional-only parameters are
+ defined by empty names.
+ (Contributed by Serhiy Storchaka in :issue:`26282`).
+
+* ``PyTraceback_Print`` method now abbreviates long sequences of repeated lines
+ as ``"[Previous line repeated {count} more times]"``.
+ (Contributed by Emanuel Barry in :issue:`26823`.)
+
+* The new :c:func:`PyErr_SetImportErrorSubclass` function allows for
+ specifying a subclass of :exc:`ImportError` to raise.
+ (Contributed by Eric Snow in :issue:`15767`.)
+
+* The new :c:func:`PyErr_ResourceWarning` function can be used to generate
+ the :exc:`ResourceWarning` providing the source of the resource allocation.
+ (Contributed by Victor Stinner in :issue:`26567`.)
+
+* The new :c:func:`PyOS_FSPath` function returns the file system
+ representation of a :term:`path-like object`.
+ (Contributed by Brett Cannon in :issue:`27186`.)
+
+* The :c:func:`PyUnicode_FSConverter` and :c:func:`PyUnicode_FSDecoder`
+ functions will now accept :term:`path-like objects <path-like object>`.
+
+
+
+Deprecated
+==========
+
+New Keywords
+------------
+
+``async`` and ``await`` are not recommended to be used as variable, class,
+function or module names. Introduced by :pep:`492` in Python 3.5, they will
+become proper keywords in Python 3.7. Starting in Python 3.6, the use of
+``async`` or ``await`` as names will generate a :exc:`DeprecationWarning`.
+
+
+Deprecated Python behavior
+--------------------------
+
+Raising the :exc:`StopIteration` exception inside a generator will now
+generate a :exc:`DeprecationWarning`, and will trigger a :exc:`RuntimeError`
+in Python 3.7. See :ref:`whatsnew-pep-479` for details.
+
+The :meth:`__aiter__` method is now expected to return an asynchronous
+iterator directly instead of returning an awaitable as previously.
+Doing the former will trigger a :exc:`DeprecationWarning`. Backward
+compatibility will be removed in Python 3.7.
+(Contributed by Yury Selivanov in :issue:`27243`.)
+
+A backslash-character pair that is not a valid escape sequence now generates
+a :exc:`DeprecationWarning`. Although this will eventually become a
+:exc:`SyntaxError`, that will not be for several Python releases.
+(Contributed by Emanuel Barry in :issue:`27364`.)
+
+When performing a relative import, falling back on ``__name__`` and
+``__path__`` from the calling module when ``__spec__`` or
+``__package__`` are not defined now raises an :exc:`ImportWarning`.
+(Contributed by Rose Ames in :issue:`25791`.)
+
+
+Deprecated Python modules, functions and methods
+------------------------------------------------
+
+asynchat
+~~~~~~~~
+
+The :mod:`asynchat` has been deprecated in favor of :mod:`asyncio`.
+(Contributed by Mariatta in :issue:`25002`.)
+
+
+asyncore
+~~~~~~~~
+
+The :mod:`asyncore` has been deprecated in favor of :mod:`asyncio`.
+(Contributed by Mariatta in :issue:`25002`.)
+
+
+dbm
+~~~
+
+Unlike other :mod:`dbm` implementations, the :mod:`dbm.dumb` module
+creates databases with the ``'rw'`` mode and allows modifying the database
+opened with the ``'r'`` mode. This behavior is now deprecated and will
+be removed in 3.8.
+(Contributed by Serhiy Storchaka in :issue:`21708`.)
+
+
+distutils
+~~~~~~~~~
+
+The undocumented ``extra_path`` argument to the
+:class:`~distutils.Distribution` constructor is now considered deprecated
+and will raise a warning if set. Support for this parameter will be
+removed in a future Python release. See :issue:`27919` for details.
+
+
+grp
+~~~
+
+The support of non-integer arguments in :func:`~grp.getgrgid` has been
+deprecated.
+(Contributed by Serhiy Storchaka in :issue:`26129`.)
+
+
+importlib
+~~~~~~~~~
+
+The :meth:`importlib.machinery.SourceFileLoader.load_module` and
+:meth:`importlib.machinery.SourcelessFileLoader.load_module` methods
+are now deprecated. They were the only remaining implementations of
+:meth:`importlib.abc.Loader.load_module` in :mod:`importlib` that had not
+been deprecated in previous versions of Python in favour of
+:meth:`importlib.abc.Loader.exec_module`.
+
+os
+~~
+
+Undocumented support of general :term:`bytes-like objects <bytes-like object>`
+as paths in :mod:`os` functions, :func:`compile` and similar functions is
+now deprecated.
+(Contributed by Serhiy Storchaka in :issue:`25791` and :issue:`26754`.)
+
+re
+~~
+
+Support for inline flags ``(?letters)`` in the middle of the regular
+expression has been deprecated and will be removed in a future Python
+version. Flags at the start of a regular expression are still allowed.
+(Contributed by Serhiy Storchaka in :issue:`22493`.)
+
+ssl
+~~~
+
+OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported.
+In the future the :mod:`ssl` module will require at least OpenSSL 1.0.2 or
+1.1.0.
+
+SSL-related arguments like ``certfile``, ``keyfile`` and ``check_hostname``
+in :mod:`ftplib`, :mod:`http.client`, :mod:`imaplib`, :mod:`poplib`,
+and :mod:`smtplib` have been deprecated in favor of ``context``.
+(Contributed by Christian Heimes in :issue:`28022`.)
+
+A couple of protocols and functions of the :mod:`ssl` module are now
+deprecated. Some features will no longer be available in future versions
+of OpenSSL. Other features are deprecated in favor of a different API.
+(Contributed by Christian Heimes in :issue:`28022` and :issue:`26470`.)
+
+tkinter
+~~~~~~~
+
+The :mod:`tkinter.tix` module is now deprecated. :mod:`tkinter` users
+should use :mod:`tkinter.ttk` instead.
+
+venv
+~~~~
+
+The ``pyvenv`` script has been deprecated in favour of ``python3 -m venv``.
+This prevents confusion as to what Python interpreter ``pyvenv`` is
+connected to and thus what Python interpreter will be used by the virtual
+environment. (Contributed by Brett Cannon in :issue:`25154`.)
+
+
+Deprecated functions and types of the C API
+-------------------------------------------
+
+Undocumented functions :c:func:`PyUnicode_AsEncodedObject`,
+:c:func:`PyUnicode_AsDecodedObject`, :c:func:`PyUnicode_AsEncodedUnicode`
+and :c:func:`PyUnicode_AsDecodedUnicode` are deprecated now.
+Use :ref:`generic codec based API <codec-registry>` instead.
+
+
+Deprecated Build Options
+------------------------
+
+The ``--with-system-ffi`` configure flag is now on by default on non-macOS
+UNIX platforms. It may be disabled by using ``--without-system-ffi``, but
+using the flag is deprecated and will not be accepted in Python 3.7.
+macOS is unaffected by this change. Note that many OS distributors already
+use the ``--with-system-ffi`` flag when building their system Python.
+
+
+Removed
+=======
+
+API and Feature Removals
+------------------------
+
+* Unknown escapes consisting of ``'\'`` and an ASCII letter in
+ regular expressions will now cause an error. The :const:`re.LOCALE`
+ flag can now only be used with binary patterns.
+
+* ``inspect.getmoduleinfo()`` was removed (was deprecated since CPython 3.3).
+ :func:`inspect.getmodulename` should be used for obtaining the module
+ name for a given path.
+ (Contributed by Yury Selivanov in :issue:`13248`.)
+
+* ``traceback.Ignore`` class and ``traceback.usage``, ``traceback.modname``,
+ ``traceback.fullmodname``, ``traceback.find_lines_from_code``,
+ ``traceback.find_lines``, ``traceback.find_strings``,
+ ``traceback.find_executable_lines`` methods were removed from the
+ :mod:`traceback` module. They were undocumented methods deprecated since
+ Python 3.2 and equivalent functionality is available from private methods.
+
+* The ``tk_menuBar()`` and ``tk_bindForTraversal()`` dummy methods in
+ :mod:`tkinter` widget classes were removed (corresponding Tk commands
+ were obsolete since Tk 4.0).
+
+* The :meth:`~zipfile.ZipFile.open` method of the :class:`zipfile.ZipFile`
+ class no longer supports the ``'U'`` mode (was deprecated since Python 3.4).
+ Use :class:`io.TextIOWrapper` for reading compressed text files in
+ :term:`universal newlines` mode.
+
+* The undocumented ``IN``, ``CDROM``, ``DLFCN``, ``TYPES``, ``CDIO``, and
+ ``STROPTS`` modules have been removed. They had been available in the
+ platform specific ``Lib/plat-*/`` directories, but were chronically out of
+ date, inconsistently available across platforms, and unmaintained. The
+ script that created these modules is still available in the source
+ distribution at :source:`Tools/scripts/h2py.py`.
+
+* The deprecated ``asynchat.fifo`` class has been removed.
+
+
+Porting to Python 3.6
+=====================
+
+This section lists previously described changes and other bugfixes
+that may require changes to your code.
+
+Changes in 'python' Command Behavior
+------------------------------------
+
+* The output of a special Python build with defined ``COUNT_ALLOCS``,
+ ``SHOW_ALLOC_COUNT`` or ``SHOW_TRACK_COUNT`` macros is now off by
+ default. It can be re-enabled using the ``-X showalloccount`` option.
+ It now outputs to ``stderr`` instead of ``stdout``.
+ (Contributed by Serhiy Storchaka in :issue:`23034`.)
+
+
+Changes in the Python API
+-------------------------
+
+* :func:`open() <open>` will no longer allow combining the ``'U'`` mode flag
+ with ``'+'``.
+ (Contributed by Jeff Balogh and John O'Connor in :issue:`2091`.)
+
+* :mod:`sqlite3` no longer implicitly commit an open transaction before DDL
+ statements.
+
+* On Linux, :func:`os.urandom` now blocks until the system urandom entropy pool
+ is initialized to increase the security.
+
+* When :meth:`importlib.abc.Loader.exec_module` is defined,
+ :meth:`importlib.abc.Loader.create_module` must also be defined.
+
+* :c:func:`PyErr_SetImportError` now sets :exc:`TypeError` when its **msg**
+ argument is not set. Previously only ``NULL`` was returned.
+
+* The format of the ``co_lnotab`` attribute of code objects changed to support
+ negative line number delta. By default, Python does not emit bytecode with
+ negative line number delta. Functions using ``frame.f_lineno``,
+ ``PyFrame_GetLineNumber()`` or ``PyCode_Addr2Line()`` are not affected.
+ Functions decoding directly ``co_lnotab`` should be updated to use a signed
+ 8-bit integer type for the line number delta, but it's only required to
+ support applications using negative line number delta. See
+ ``Objects/lnotab_notes.txt`` for the ``co_lnotab`` format and how to decode
+ it, and see the :pep:`511` for the rationale.
+
+* The functions in the :mod:`compileall` module now return booleans instead
+ of ``1`` or ``0`` to represent success or failure, respectively. Thanks to
+ booleans being a subclass of integers, this should only be an issue if you
+ were doing identity checks for ``1`` or ``0``. See :issue:`25768`.
+
+* Reading the :attr:`~urllib.parse.SplitResult.port` attribute of
+ :func:`urllib.parse.urlsplit` and :func:`~urllib.parse.urlparse` results
+ now raises :exc:`ValueError` for out-of-range values, rather than
+ returning :const:`None`. See :issue:`20059`.
+
+* The :mod:`imp` module now raises a :exc:`DeprecationWarning` instead of
+ :exc:`PendingDeprecationWarning`.
+
+* The following modules have had missing APIs added to their :attr:`__all__`
+ attributes to match the documented APIs:
+ :mod:`calendar`, :mod:`cgi`, :mod:`csv`,
+ :mod:`~xml.etree.ElementTree`, :mod:`enum`,
+ :mod:`fileinput`, :mod:`ftplib`, :mod:`logging`, :mod:`mailbox`,
+ :mod:`mimetypes`, :mod:`optparse`, :mod:`plistlib`, :mod:`smtpd`,
+ :mod:`subprocess`, :mod:`tarfile`, :mod:`threading` and
+ :mod:`wave`. This means they will export new symbols when ``import *``
+ is used.
+ (Contributed by Joel Taddei and Jacek Kołodziej in :issue:`23883`.)
+
+* When performing a relative import, if ``__package__`` does not compare equal
+ to ``__spec__.parent`` then :exc:`ImportWarning` is raised.
+ (Contributed by Brett Cannon in :issue:`25791`.)
+
+* When a relative import is performed and no parent package is known, then
+ :exc:`ImportError` will be raised. Previously, :exc:`SystemError` could be
+ raised. (Contributed by Brett Cannon in :issue:`18018`.)
+
+* Servers based on the :mod:`socketserver` module, including those
+ defined in :mod:`http.server`, :mod:`xmlrpc.server` and
+ :mod:`wsgiref.simple_server`, now only catch exceptions derived
+ from :exc:`Exception`. Therefore if a request handler raises
+ an exception like :exc:`SystemExit` or :exc:`KeyboardInterrupt`,
+ :meth:`~socketserver.BaseServer.handle_error` is no longer called, and
+ the exception will stop a single-threaded server. (Contributed by
+ Martin Panter in :issue:`23430`.)
+
+* :func:`spwd.getspnam` now raises a :exc:`PermissionError` instead of
+ :exc:`KeyError` if the user doesn't have privileges.
+
+* The :meth:`socket.socket.close` method now raises an exception if
+ an error (e.g. ``EBADF``) was reported by the underlying system call.
+ (Contributed by Martin Panter in :issue:`26685`.)
+
+* The *decode_data* argument for :class:`smtpd.SMTPChannel` and
+ :class:`smtpd.SMTPServer` constructors is now ``False`` by default.
+ This means that the argument passed to
+ :meth:`~smtpd.SMTPServer.process_message` is now a bytes object by
+ default, and ``process_message()`` will be passed keyword arguments.
+ Code that has already been updated in accordance with the deprecation
+ warning generated by 3.5 will not be affected.
+
+* All optional arguments of the :func:`~json.dump`, :func:`~json.dumps`,
+ :func:`~json.load` and :func:`~json.loads` functions and
+ :class:`~json.JSONEncoder` and :class:`~json.JSONDecoder` class
+ constructors in the :mod:`json` module are now :ref:`keyword-only
+ <keyword-only_parameter>`.
+ (Contributed by Serhiy Storchaka in :issue:`18726`.)
+
+* Subclasses of :class:`type` which don't override ``type.__new__`` may no
+ longer use the one-argument form to get the type of an object.
+
+* As part of :pep:`487`, the handling of keyword arguments passed to
+ :class:`type` (other than the metaclass hint, ``metaclass``) is now
+ consistently delegated to :meth:`object.__init_subclass__`. This means that
+ :meth:`type.__new__` and :meth:`type.__init__` both now accept arbitrary
+ keyword arguments, but :meth:`object.__init_subclass__` (which is called from
+ :meth:`type.__new__`) will reject them by default. Custom metaclasses
+ accepting additional keyword arguments will need to adjust their calls to
+ :meth:`type.__new__` (whether direct or via :class:`super`) accordingly.
+
+* In :class:`distutils.command.sdist.sdist`, the ``default_format``
+ attribute has been removed and is no longer honored. Instead, the
+ gzipped tarfile format is the default on all platforms and no
+ platform-specific selection is made.
+ In environments where distributions are
+ built on Windows and zip distributions are required, configure
+ the project with a ``setup.cfg`` file containing the following::
+
+ [sdist]
+ formats=zip
+
+ This behavior has also been backported to earlier Python versions
+ by Setuptools 26.0.0.
+
+* In the :mod:`urllib.request` module and the
+ :meth:`http.client.HTTPConnection.request` method, if no Content-Length
+ header field has been specified and the request body is a file object,
+ it is now sent with HTTP 1.1 chunked encoding. If a file object has to
+ be sent to a HTTP 1.0 server, the Content-Length value now has to be
+ specified by the caller.
+ (Contributed by Demian Brecht and Rolf Krahl with tweaks from
+ Martin Panter in :issue:`12319`.)
+
+* The :class:`~csv.DictReader` now returns rows of type
+ :class:`~collections.OrderedDict`.
+ (Contributed by Steve Holden in :issue:`27842`.)
+
+* The :const:`crypt.METHOD_CRYPT` will no longer be added to ``crypt.methods``
+ if unsupported by the platform.
+ (Contributed by Victor Stinner in :issue:`25287`.)
+
+* The *verbose* and *rename* arguments for
+ :func:`~collections.namedtuple` are now keyword-only.
+ (Contributed by Raymond Hettinger in :issue:`25628`.)
+
+* On Linux, :func:`ctypes.util.find_library` now looks in
+ ``LD_LIBRARY_PATH`` for shared libraries.
+ (Contributed by Vinay Sajip in :issue:`9998`.)
+
+* The :class:`imaplib.IMAP4` class now handles flags containing the
+ ``']'`` character in messages sent from the server to improve
+ real-world compatibility.
+ (Contributed by Lita Cho in :issue:`21815`.)
+
+* The :func:`mmap.write() <mmap.write>` function now returns the number
+ of bytes written like other write methods.
+ (Contributed by Jakub Stasiak in :issue:`26335`.)
+
+* The :func:`pkgutil.iter_modules` and :func:`pkgutil.walk_packages`
+ functions now return :class:`~pkgutil.ModuleInfo` named tuples.
+ (Contributed by Ramchandra Apte in :issue:`17211`.)
+
+* :func:`re.sub` now raises an error for invalid numerical group
+ reference in replacement template even if the pattern is not
+ found in the string. Error message for invalid group reference
+ now includes the group index and the position of the reference.
+ (Contributed by SilentGhost, Serhiy Storchaka in :issue:`25953`.)
+
+* :class:`zipfile.ZipFile` will now raise :exc:`NotImplementedError` for
+ unrecognized compression values. Previously a plain :exc:`RuntimeError`
+ was raised. Additionally, calling :class:`~zipfile.ZipFile` methods or
+ on a closed ZipFile or calling :meth:`~zipfile.ZipFile.write` methods
+ on a ZipFile created with mode ``'r'`` will raise a :exc:`ValueError`.
+ Previously, a :exc:`RuntimeError` was raised in those scenarios.
+
+
+Changes in the C API
+--------------------
+
+* :c:func:`PyMem_Malloc` allocator family now uses the :ref:`pymalloc allocator
+ <pymalloc>` rather than system :c:func:`malloc`. Applications calling
+ :c:func:`PyMem_Malloc` without holding the GIL can now crash. Set the
+ :envvar:`PYTHONMALLOC` environment variable to ``debug`` to validate the
+ usage of memory allocators in your application. See :issue:`26249`.
+
+* :c:func:`Py_Exit` (and the main interpreter) now override the exit status
+ with 120 if flushing buffered data failed. See :issue:`5319`.
projects / python / commitdiff