kbe/src/lib/python/Doc/whatsnew/3.5.rst
What's New In Python 3.5
:Editors: Elvis Pranskevichus [email protected], Yury Selivanov [email protected]
.. 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.
This article explains the new features in Python 3.5, compared to 3.4.
Python 3.5 was released on September 13, 2015. See the
changelog <https://docs.python.org/3.5/whatsnew/changelog.html>_ for a full
list of changes.
.. seealso::
:pep:`478` - Python 3.5 Release Schedule
New syntax features:
PEP 492 <whatsnew-pep-492>, coroutines with async and await syntax.PEP 465 <whatsnew-pep-465>, a new matrix multiplication operator: a @ b.PEP 448 <whatsnew-pep-448>, additional unpacking generalizations.New library modules:
typing: :ref:PEP 484 -- Type Hints <whatsnew-pep-484>.zipapp: :ref:PEP 441 Improving Python ZIP Application Support <whatsnew-zipapp>.New built-in features:
bytes % args, bytearray % args: :ref:PEP 461 <whatsnew-pep-461> --
Adding % formatting to bytes and bytearray.
New :meth:bytes.hex, :meth:bytearray.hex and :meth:memoryview.hex
methods. (Contributed by Arnon Yaari in :issue:9951.)
:class:memoryview now supports tuple indexing (including multi-dimensional).
(Contributed by Antoine Pitrou in :issue:23632.)
Generators have a new gi_yieldfrom attribute, which returns the
object being iterated by yield from expressions. (Contributed
by Benno Leslie and Yury Selivanov in :issue:24450.)
A new :exc:RecursionError exception is now raised when maximum
recursion depth is reached. (Contributed by Georg Brandl
in :issue:19235.)
CPython implementation improvements:
When the LC_TYPE locale is the POSIX locale (C locale),
:py:data:sys.stdin and :py:data:sys.stdout now use the
surrogateescape error handler, instead of the strict error handler.
(Contributed by Victor Stinner in :issue:19977.)
.pyo files are no longer used and have been replaced by a more flexible
scheme that includes the optimization level explicitly in .pyc name.
(See :ref:PEP 488 overview <whatsnew-pep-488>.)
Builtin and extension modules are now initialized in a multi-phase process,
which is similar to how Python modules are loaded.
(See :ref:PEP 489 overview <whatsnew-pep-489>.)
Significant improvements in the standard library:
:class:collections.OrderedDict is now
:ref:implemented in C <whatsnew-ordereddict>, which makes it
4 to 100 times faster.
The :mod:ssl module gained
:ref:support for Memory BIO <whatsnew-sslmemorybio>, which decouples SSL
protocol handling from network IO.
The new :func:os.scandir function provides a
:ref:better and significantly faster way <whatsnew-pep-471>
of directory traversal.
:func:functools.lru_cache has been mostly
:ref:reimplemented in C <whatsnew-lrucache>, yielding much better
performance.
The new :func:subprocess.run function provides a
:ref:streamlined way to run subprocesses <whatsnew-subprocess>.
The :mod:traceback module has been significantly
:ref:enhanced <whatsnew-traceback> for improved
performance and developer convenience.
Security improvements:
SSLv3 is now disabled throughout the standard library.
It can still be enabled by instantiating a :class:ssl.SSLContext
manually. (See :issue:22638 for more details; this change was
backported to CPython 3.4 and 2.7.)
HTTP cookie parsing is now stricter, in order to protect
against potential injection attacks. (Contributed by Antoine Pitrou
in :issue:22796.)
Windows improvements:
A new installer for Windows has replaced the old MSI.
See :ref:using-on-windows for more information.
Windows builds now use Microsoft Visual C++ 14.0, and extension modules should use the same.
Please read on for a comprehensive list of user-facing changes, including many other smaller improvements, CPython optimizations, deprecations, and potential porting issues.
.. _whatsnew-pep-492:
:pep:492 greatly improves support for asynchronous programming in Python
by adding :term:awaitable objects <awaitable>,
:term:coroutine functions <coroutine function>,
:term:asynchronous iteration <asynchronous iterable>,
and :term:asynchronous context managers <asynchronous context manager>.
Coroutine functions are declared using the new :keyword:async def syntax::
>>> async def coro():
... return 'spam'
Inside a coroutine function, the new :keyword:await expression can be used
to suspend coroutine execution until the result is available. Any object
can be awaited, as long as it implements the :term:awaitable protocol by
defining the :meth:__await__ method.
PEP 492 also adds :keyword:async for statement for convenient iteration
over asynchronous iterables.
An example of a rudimentary HTTP client written using the new syntax::
import asyncio
async def http_get(domain):
reader, writer = await asyncio.open_connection(domain, 80)
writer.write(b'\r\n'.join([
b'GET / HTTP/1.1',
b'Host: %b' % domain.encode('latin-1'),
b'Connection: close',
b'', b''
]))
async for line in reader:
print('>>>', line)
writer.close()
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(http_get('example.com'))
finally:
loop.close()
Similarly to asynchronous iteration, there is a new syntax for asynchronous context managers. The following script::
import asyncio
async def coro(name, lock):
print('coro {}: waiting for lock'.format(name))
async with lock:
print('coro {}: holding the lock'.format(name))
await asyncio.sleep(1)
print('coro {}: releasing the lock'.format(name))
loop = asyncio.get_event_loop()
lock = asyncio.Lock()
coros = asyncio.gather(coro(1, lock), coro(2, lock))
try:
loop.run_until_complete(coros)
finally:
loop.close()
will output::
coro 2: waiting for lock
coro 2: holding the lock
coro 1: waiting for lock
coro 2: releasing the lock
coro 1: holding the lock
coro 1: releasing the lock
Note that both :keyword:async for and :keyword:async with can only
be used inside a coroutine function declared with :keyword:async def.
Coroutine functions are intended to be run inside a compatible event loop,
such as the :ref:asyncio loop <asyncio-event-loop>.
.. note::
.. versionchanged:: 3.5.2
Starting with CPython 3.5.2, __aiter__ can directly return
:term:asynchronous iterators <asynchronous iterator>. Returning
an :term:awaitable object will result in a
:exc:PendingDeprecationWarning.
See more details in the :ref:`async-iterators` documentation
section.
.. seealso::
:pep:492 -- Coroutines with async and await syntax
PEP written and implemented by Yury Selivanov.
.. _whatsnew-pep-465:
:pep:465 adds the @ infix operator for matrix multiplication.
Currently, no builtin Python types implement the new operator, however, it
can be implemented by defining :meth:__matmul__, :meth:__rmatmul__,
and :meth:__imatmul__ for regular, reflected, and in-place matrix
multiplication. The semantics of these methods is similar to that of
methods defining other infix arithmetic operators.
Matrix multiplication is a notably common operation in many fields of
mathematics, science, engineering, and the addition of @ allows writing
cleaner code::
S = (H @ beta - r).T @ inv(H @ V @ H.T) @ (H @ beta - r)
instead of::
S = dot((dot(H, beta) - r).T,
dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))
NumPy 1.10 has support for the new operator::
>>> import numpy
>>> x = numpy.ones(3)
>>> x
array([ 1., 1., 1.])
>>> m = numpy.eye(3)
>>> m
array([[ 1., 0., 0.],
[ 0., 1., 0.],
[ 0., 0., 1.]])
>>> x @ m
array([ 1., 1., 1.])
.. seealso::
:pep:465 -- A dedicated infix operator for matrix multiplication
PEP written by Nathaniel J. Smith; implemented by Benjamin Peterson.
.. _whatsnew-pep-448:
:pep:448 extends the allowed uses of the * iterable unpacking
operator and ** dictionary unpacking operator. It is now possible
to use an arbitrary number of unpackings in :ref:function calls <calls>::
>>> print(*[1], *[2], 3, *[4, 5])
1 2 3 4 5
>>> def fn(a, b, c, d):
... print(a, b, c, d)
...
>>> fn(**{'a': 1, 'c': 3}, **{'b': 2, 'd': 4})
1 2 3 4
Similarly, tuple, list, set, and dictionary displays allow multiple
unpackings (see :ref:exprlists and :ref:dict)::
>>> *range(4), 4
(0, 1, 2, 3, 4)
>>> [*range(4), 4]
[0, 1, 2, 3, 4]
>>> {*range(4), 4, *(5, 6, 7)}
{0, 1, 2, 3, 4, 5, 6, 7}
>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}
.. seealso::
:pep:448 -- Additional Unpacking Generalizations
PEP written by Joshua Landau; implemented by Neil Girdhar,
Thomas Wouters, and Joshua Landau.
.. _whatsnew-pep-461:
:pep:461 adds support for the %
:ref:interpolation operator <bytes-formatting> to :class:bytes
and :class:bytearray.
While interpolation is usually thought of as a string operation, there are
cases where interpolation on bytes or bytearrays makes sense, and the
work needed to make up for this missing functionality detracts from the
overall readability of the code. This issue is particularly important when
dealing with wire format protocols, which are often a mixture of binary
and ASCII compatible text.
Examples::
>>> b'Hello %b!' % b'World'
b'Hello World!'
>>> b'x=%i y=%f' % (1, 2.5)
b'x=1 y=2.500000'
Unicode is not allowed for %b, but it is accepted by %a (equivalent of
repr(obj).encode('ascii', 'backslashreplace'))::
>>> b'Hello %b!' % 'World'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: %b requires bytes, or an object that implements __bytes__, not 'str'
>>> b'price: %a' % '10€'
b"price: '10\\u20ac'"
Note that %s and %r conversion types, although supported, should
only be used in codebases that need compatibility with Python 2.
.. seealso::
:pep:461 -- Adding % formatting to bytes and bytearray
PEP written by Ethan Furman; implemented by Neil Schemenauer and
Ethan Furman.
.. _whatsnew-pep-484:
Function annotation syntax has been a Python feature since version 3.0
(:pep:3107), however the semantics of annotations has been left undefined.
Experience has shown that the majority of function annotation uses were to provide type hints to function parameters and return values. It became evident that it would be beneficial for Python users, if the standard library included the base definitions and tools for type annotations.
:pep:484 introduces a :term:provisional module <provisional api> to
provide these standard definitions and tools, along with some conventions
for situations where annotations are not available.
For example, here is a simple function whose argument and return type are declared in the annotations::
def greeting(name: str) -> str:
return 'Hello ' + name
While these annotations are available at runtime through the usual
:attr:__annotations__ attribute, no automatic type checking happens at
runtime. Instead, it is assumed that a separate off-line type checker
(e.g. mypy <http://mypy-lang.org>_) will be used for on-demand
source code analysis.
The type system supports unions, generic types, and a special type
named :class:~typing.Any which is consistent with (i.e. assignable to
and from) all types.
.. seealso::
typing module documentation484 -- Type Hints
PEP written by Guido van Rossum, Jukka Lehtosalo, and Łukasz Langa;
implemented by Guido van Rossum.483 -- The Theory of Type Hints
PEP written by Guido van Rossum.. _whatsnew-pep-471:
:pep:471 adds a new directory iteration function, :func:os.scandir,
to the standard library. Additionally, :func:os.walk is now
implemented using scandir, which makes it 3 to 5 times faster
on POSIX systems and 7 to 20 times faster on Windows systems. This is
largely achieved by greatly reducing the number of calls to :func:os.stat
required to walk a directory tree.
Additionally, scandir returns an iterator, as opposed to returning
a list of file names, which improves memory efficiency when iterating
over very large directories.
The following example shows a simple use of :func:os.scandir to display all
the files (excluding directories) in the given path that don't start with
'.'. The :meth:entry.is_file() <os.DirEntry.is_file> call will generally
not make an additional system call::
for entry in os.scandir(path):
if not entry.name.startswith('.') and entry.is_file():
print(entry.name)
.. seealso::
:pep:471 -- os.scandir() function -- a better and faster directory iterator
PEP written and implemented by Ben Hoyt with the help of Victor Stinner.
.. _whatsnew-pep-475:
An :py:data:errno.EINTR error code is returned whenever a system call, that
is waiting for I/O, is interrupted by a signal. Previously, Python would
raise :exc:InterruptedError in such cases. This meant that, when writing a
Python application, the developer had two choices:
#. Ignore the InterruptedError.
#. Handle the InterruptedError and attempt to restart the interrupted
system call at every call site.
The first option makes an application fail intermittently. The second option adds a large amount of boilerplate that makes the code nearly unreadable. Compare::
print("Hello World")
and::
while True:
try:
print("Hello World")
break
except InterruptedError:
continue
:pep:475 implements automatic retry of system calls on
EINTR. This removes the burden of dealing with EINTR
or :exc:InterruptedError in user code in most situations and makes
Python programs, including the standard library, more robust. Note that
the system call is only retried if the signal handler does not raise an
exception.
Below is a list of functions which are now retried when interrupted by a signal:
:func:open and :func:io.open;
functions of the :mod:faulthandler module;
:mod:os functions: :func:~os.fchdir, :func:~os.fchmod,
:func:~os.fchown, :func:~os.fdatasync, :func:~os.fstat,
:func:~os.fstatvfs, :func:~os.fsync, :func:~os.ftruncate,
:func:~os.mkfifo, :func:~os.mknod, :func:~os.open,
:func:~os.posix_fadvise, :func:~os.posix_fallocate, :func:~os.pread,
:func:~os.pwrite, :func:~os.read, :func:~os.readv, :func:~os.sendfile,
:func:~os.wait3, :func:~os.wait4, :func:~os.wait,
:func:~os.waitid, :func:~os.waitpid, :func:~os.write,
:func:~os.writev;
special cases: :func:os.close and :func:os.dup2 now ignore
:py:data:~errno.EINTR errors; the syscall is not retried (see the PEP
for the rationale);
:mod:select functions: :func:devpoll.poll() <select.devpoll.poll>,
:func:epoll.poll() <select.epoll.poll>,
:func:kqueue.control() <select.kqueue.control>,
:func:poll.poll() <select.poll.poll>, :func:~select.select;
methods of the :class:~socket.socket class: :meth:~socket.socket.accept,
:meth:~socket.socket.connect (except for non-blocking sockets),
:meth:~socket.socket.recv, :meth:~socket.socket.recvfrom,
:meth:~socket.socket.recvmsg, :meth:~socket.socket.send,
:meth:~socket.socket.sendall, :meth:~socket.socket.sendmsg,
:meth:~socket.socket.sendto;
:func:signal.sigtimedwait and :func:signal.sigwaitinfo;
:func:time.sleep.
.. seealso::
:pep:475 -- Retry system calls failing with EINTR
PEP and implementation written by Charles-François Natali and
Victor Stinner, with the help of Antoine Pitrou (the French connection).
.. _whatsnew-pep-479:
The interaction of generators and :exc:StopIteration in Python 3.4 and
earlier was sometimes surprising, and could conceal obscure bugs. Previously,
StopIteration raised accidentally inside a generator function was
interpreted as the end of the iteration by the loop construct driving the
generator.
:pep:479 changes the behavior of generators: when a StopIteration
exception is raised inside a generator, it is replaced with a
:exc:RuntimeError before it exits the generator frame. The main goal of
this change is to ease debugging in the situation where an unguarded
:func:next call raises StopIteration and causes the iteration controlled
by the generator to terminate silently. This is particularly pernicious in
combination with the yield from construct.
This is a backwards incompatible change, so to enable the new behavior,
a :term:__future__ import is necessary::
>>> from __future__ import generator_stop
>>> def gen():
... next(iter([]))
... yield
...
>>> next(gen())
Traceback (most recent call last):
File "<stdin>", line 2, in gen
StopIteration
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: generator raised StopIteration
Without a __future__ import, a :exc:PendingDeprecationWarning will be
raised whenever a :exc:StopIteration exception is raised inside a generator.
.. seealso::
:pep:479 -- Change StopIteration handling inside generators
PEP written by Chris Angelico and Guido van Rossum. Implemented by
Chris Angelico, Yury Selivanov and Nick Coghlan.
.. _whatsnew-pep-485:
:pep:485 adds the :func:math.isclose and :func:cmath.isclose
functions which tell whether two values are approximately equal or
"close" to each other. Whether or not two values are considered
close is determined according to given absolute and relative tolerances.
Relative tolerance is the maximum allowed difference between isclose
arguments, relative to the larger absolute value::
>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, rel_tol=1e-5)
True
>>> math.isclose(a, b, rel_tol=1e-6)
False
It is also possible to compare two values using absolute tolerance, which must be a non-negative value::
>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, abs_tol=0.00003)
True
>>> math.isclose(a, b, abs_tol=0.00001)
False
.. seealso::
:pep:485 -- A function for testing approximate equality
PEP written by Christopher Barker; implemented by Chris Barker and
Tal Einat.
.. _whatsnew-pep-486:
:pep:486 makes the Windows launcher (see :pep:397) aware of an active
virtual environment. When the default interpreter would be used and the
VIRTUAL_ENV environment variable is set, the interpreter in the virtual
environment will be used.
.. seealso::
:pep:`486` -- Make the Python Launcher aware of virtual environments
PEP written and implemented by Paul Moore.
.. _whatsnew-pep-488:
:pep:488 does away with the concept of .pyo files. This means that
.pyc files represent both unoptimized and optimized bytecode. To prevent the
need to constantly regenerate bytecode files, .pyc files now have an
optional opt- tag in their name when the bytecode is optimized. This has the
side-effect of no more bytecode file name clashes when running under either
:option:-O or :option:-OO. Consequently, bytecode files generated from
:option:-O, and :option:-OO may now exist simultaneously.
:func:importlib.util.cache_from_source has an updated API to help with
this change.
.. seealso::
:pep:488 -- Elimination of PYO files
PEP written and implemented by Brett Cannon.
.. _whatsnew-pep-489:
:pep:489 updates extension module initialization to take advantage of the
two step module loading mechanism introduced by :pep:451 in Python 3.4.
This change brings the import semantics of extension modules that opt-in to using the new mechanism much closer to those of Python source and bytecode modules, including the ability to use any valid identifier as a module name, rather than being restricted to ASCII.
.. seealso::
:pep:489 -- Multi-phase extension module initialization
PEP written by Petr Viktorin, Stefan Behnel, and Nick Coghlan;
implemented by Petr Viktorin.
Some smaller changes made to the core Python language are:
Added the "namereplace" error handlers. The "backslashreplace"
error handlers now work with decoding and translating.
(Contributed by Serhiy Storchaka in :issue:19676 and :issue:22286.)
The :option:-b option now affects comparisons of :class:bytes with
:class:int. (Contributed by Serhiy Storchaka in :issue:23681.)
New Kazakh kz1048 and Tajik koi8_t :ref:codecs <standard-encodings>.
(Contributed by Serhiy Storchaka in :issue:22682 and :issue:22681.)
Property docstrings are now writable. This is especially useful for
:func:collections.namedtuple docstrings.
(Contributed by Berker Peksag in :issue:24064.)
Circular imports involving relative imports are now supported.
(Contributed by Brett Cannon and Antoine Pitrou in :issue:17636.)
The new :mod:typing :term:provisional <provisional api> module
provides standard definitions and tools for function type annotations.
See :ref:Type Hints <whatsnew-pep-484> for more information.
.. _whatsnew-zipapp:
The new :mod:zipapp module (specified in :pep:441) provides an API and
command line tool for creating executable Python Zip Applications, which
were introduced in Python 2.6 in :issue:1739468, but which were not well
publicized, either at the time or since.
With the new module, bundling your application is as simple as putting all
the files, including a __main__.py file, into a directory myapp
and running:
.. code-block:: shell-session
$ python -m zipapp myapp
$ python myapp.pyz
The module implementation has been contributed by Paul Moore in
:issue:23491.
.. seealso::
:pep:441 -- Improving Python ZIP Application Support
The :class:~argparse.ArgumentParser class now allows disabling
:ref:abbreviated usage <prefix-matching> of long options by setting
:ref:allow_abbrev to False. (Contributed by Jonathan Paugh,
Steven Bethard, paul j3 and Daniel Eriksson in :issue:14910.)
Since the :mod:asyncio module is :term:provisional <provisional api>,
all changes introduced in Python 3.5 have also been backported to Python 3.4.x.
Notable changes in the :mod:asyncio module since Python 3.4.0:
New debugging APIs: :meth:loop.set_debug() <asyncio.loop.set_debug>
and :meth:loop.get_debug() <asyncio.loop.get_debug> methods.
(Contributed by Victor Stinner.)
The proactor event loop now supports SSL.
(Contributed by Antoine Pitrou and Victor Stinner in :issue:22560.)
A new :meth:loop.is_closed() <asyncio.loop.is_closed> method to
check if the event loop is closed.
(Contributed by Victor Stinner in :issue:21326.)
A new :meth:loop.create_task() <asyncio.loop.create_task>
to conveniently create and schedule a new :class:~asyncio.Task
for a coroutine. The create_task method is also used by all
asyncio functions that wrap coroutines into tasks, such as
:func:asyncio.wait, :func:asyncio.gather, etc.
(Contributed by Victor Stinner.)
A new :meth:transport.get_write_buffer_limits() <asyncio.WriteTransport.get_write_buffer_limits>
method to inquire for high- and low- water limits of the flow
control.
(Contributed by Victor Stinner.)
The :func:~asyncio.async function is deprecated in favor of
:func:~asyncio.ensure_future.
(Contributed by Yury Selivanov.)
New :meth:loop.set_task_factory() <asyncio.loop.set_task_factory> and
:meth:loop.get_task_factory() <asyncio.loop.get_task_factory>
methods to customize the task factory that :meth:loop.create_task() <asyncio.loop.create_task> method uses. (Contributed by Yury
Selivanov.)
New :meth:Queue.join() <asyncio.Queue.join> and
:meth:Queue.task_done() <asyncio.Queue.task_done> queue methods.
(Contributed by Victor Stinner.)
The JoinableQueue class was removed, in favor of the
:class:asyncio.Queue class.
(Contributed by Victor Stinner.)
Updates in 3.5.1:
The :func:~asyncio.ensure_future function and all functions that
use it, such as :meth:loop.run_until_complete() <asyncio.loop.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.loop.create_server>
method can now accept a list of hosts.
(Contributed by Yann Sionneau.)
Updates in 3.5.2:
New :meth:loop.create_future() <asyncio.loop.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.)
New :meth:loop.get_exception_handler() <asyncio.loop.get_exception_handler>
method to get the current exception handler.
(Contributed by Yury Selivanov.)
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 :meth:loop.create_connection() <asyncio.loop.create_connection>
and :meth:loop.create_server() <asyncio.loop.create_server>
methods are optimized to avoid calling the system getaddrinfo
function if the address is already resolved.
(Contributed by A. Jesse Jiryu Davis.)
The :meth:loop.sock_connect(sock, address) <asyncio.loop.sock_connect>
no longer requires the address to be resolved prior to the call.
(Contributed by A. Jesse Jiryu Davis.)
The :meth:BZ2Decompressor.decompress <bz2.BZ2Decompressor.decompress>
method now accepts an optional max_length argument to limit the maximum
size of decompressed data. (Contributed by Nikolaus Rath in :issue:15955.)
The :class:~cgi.FieldStorage class now supports the :term:context manager
protocol. (Contributed by Berker Peksag in :issue:20289.)
A new function :func:~cmath.isclose provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in :issue:24270.)
The :func:InteractiveInterpreter.showtraceback() <code.InteractiveInterpreter.showtraceback>
method now prints the full chained traceback, just like the interactive
interpreter. (Contributed by Claudiu Popa in :issue:17442.)
.. _whatsnew-ordereddict:
The :class:~collections.OrderedDict class is now implemented in C, which
makes it 4 to 100 times faster. (Contributed by Eric Snow in :issue:16991.)
:meth:OrderedDict.items() <collections.OrderedDict.items>,
:meth:OrderedDict.keys() <collections.OrderedDict.keys>,
:meth:OrderedDict.values() <collections.OrderedDict.values> views now support
:func:reversed iteration.
(Contributed by Serhiy Storchaka in :issue:19505.)
The :class:~collections.deque class now defines
:meth:~collections.deque.index, :meth:~collections.deque.insert, and
:meth:~collections.deque.copy, and supports the + and * operators.
This allows deques to be recognized as a :class:~collections.abc.MutableSequence
and improves their substitutability for lists.
(Contributed by Raymond Hettinger in :issue:23704.)
Docstrings produced by :func:~collections.namedtuple can now be updated::
Point = namedtuple('Point', ['x', 'y'])
Point.__doc__ += ': Cartesian coodinate'
Point.x.__doc__ = 'abscissa'
Point.y.__doc__ = 'ordinate'
(Contributed by Berker Peksag in :issue:24064.)
The :class:~collections.UserString class now implements the
:meth:__getnewargs__, :meth:__rmod__, :meth:~str.casefold,
:meth:~str.format_map, :meth:~str.isprintable, and :meth:~str.maketrans
methods to match the corresponding methods of :class:str.
(Contributed by Joe Jevnik in :issue:22189.)
The :meth:Sequence.index() <collections.abc.Sequence.index> method now
accepts start and stop arguments to match the corresponding methods
of :class:tuple, :class:list, etc.
(Contributed by Devin Jeanpierre in :issue:23086.)
A new :class:~collections.abc.Generator abstract base class. (Contributed
by Stefan Behnel in :issue:24018.)
New :class:~collections.abc.Awaitable, :class:~collections.abc.Coroutine,
:class:~collections.abc.AsyncIterator, and
:class:~collections.abc.AsyncIterable abstract base classes.
(Contributed by Yury Selivanov in :issue:24184.)
For earlier Python versions, a backport of the new ABCs is available in an
external PyPI package <https://pypi.org/project/backports_abc>_.
A new :mod:compileall option, :samp:-j {N}, allows running N workers
simultaneously to perform parallel bytecode compilation.
The :func:~compileall.compile_dir function has a corresponding workers
parameter. (Contributed by Claudiu Popa in :issue:16104.)
Another new option, -r, allows controlling the maximum recursion
level for subdirectories. (Contributed by Claudiu Popa in :issue:19628.)
The -q command line option can now be specified more than once, in
which case all output, including errors, will be suppressed. The corresponding
quiet parameter in :func:~compileall.compile_dir,
:func:~compileall.compile_file, and :func:~compileall.compile_path can now
accept an integer value indicating the level of output suppression.
(Contributed by Thomas Kluyver in :issue:21338.)
The :meth:Executor.map() <concurrent.futures.Executor.map> method now accepts a
chunksize argument to allow batching of tasks to improve performance when
:meth:~concurrent.futures.ProcessPoolExecutor is used.
(Contributed by Dan O'Reilly in :issue:11271.)
The number of workers in the :class:~concurrent.futures.ThreadPoolExecutor
constructor is optional now. The default value is 5 times the number of CPUs.
(Contributed by Claudiu Popa in :issue:21527.)
:mod:configparser now provides a way to customize the conversion
of values by specifying a dictionary of converters in the
:class:~configparser.ConfigParser constructor, or by defining them
as methods in ConfigParser subclasses. Converters defined in
a parser instance are inherited by its section proxies.
Example::
>>> import configparser
>>> conv = {}
>>> conv['list'] = lambda v: [e.strip() for e in v.split() if e.strip()]
>>> cfg = configparser.ConfigParser(converters=conv)
>>> cfg.read_string("""
... [s]
... list = a b c d e f g
... """)
>>> cfg.get('s', 'list')
'a b c d e f g'
>>> cfg.getlist('s', 'list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> section = cfg['s']
>>> section.getlist('list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']
(Contributed by Łukasz Langa in :issue:18159.)
The new :func:~contextlib.redirect_stderr :term:context manager (similar to
:func:~contextlib.redirect_stdout) makes it easier for utility scripts to
handle inflexible APIs that write their output to :data:sys.stderr and
don't provide any options to redirect it::
>>> import contextlib, io, logging
>>> f = io.StringIO()
>>> with contextlib.redirect_stderr(f):
... logging.warning('warning')
...
>>> f.getvalue()
'WARNING:root:warning\n'
(Contributed by Berker Peksag in :issue:22389.)
The :meth:~csv.csvwriter.writerow method now supports arbitrary iterables,
not just sequences. (Contributed by Serhiy Storchaka in :issue:23171.)
The new :func:~curses.update_lines_cols function updates the :envvar:LINES
and :envvar:COLS environment variables. This is useful for detecting
manual screen resizing. (Contributed by Arnon Yaari in :issue:4254.)
:func:dumb.open <dbm.dumb.open> always creates a new database when the flag
has the value "n". (Contributed by Claudiu Popa in :issue:18039.)
The charset of HTML documents generated by
:meth:HtmlDiff.make_file() <difflib.HtmlDiff.make_file>
can now be customized by using a new charset keyword-only argument.
The default charset of HTML document changed from "ISO-8859-1"
to "utf-8".
(Contributed by Berker Peksag in :issue:2052.)
The :func:~difflib.diff_bytes function can now compare lists of byte
strings. This fixes a regression from Python 2.
(Contributed by Terry J. Reedy and Greg Ward in :issue:17445.)
Both the build and build_ext commands now accept a -j option to
enable parallel building of extension modules.
(Contributed by Antoine Pitrou in :issue:5309.)
The :mod:distutils module now supports xz compression, and can be
enabled by passing xztar as an argument to bdist --format.
(Contributed by Serhiy Storchaka in :issue:16314.)
The :func:~doctest.DocTestSuite function returns an empty
:class:unittest.TestSuite if module contains no docstrings, instead of
raising :exc:ValueError. (Contributed by Glenn Jones in :issue:15916.)
A new policy option :attr:Policy.mangle_from_ <email.policy.Policy.mangle_from_>
controls whether or not lines that start with "From " in email bodies are
prefixed with a ">" character by generators. The default is True for
:attr:~email.policy.compat32 and False for all other policies.
(Contributed by Milan Oberkirch in :issue:20098.)
A new
:meth:Message.get_content_disposition() <email.message.Message.get_content_disposition>
method provides easy access to a canonical value for the
:mailheader:Content-Disposition header.
(Contributed by Abhilash Raj in :issue:21083.)
A new policy option :attr:EmailPolicy.utf8 <email.policy.EmailPolicy.utf8>
can be set to True to encode email headers using the UTF-8 charset instead
of using encoded words. This allows Messages to be formatted according to
:rfc:6532 and used with an SMTP server that supports the :rfc:6531
SMTPUTF8 extension. (Contributed by R. David Murray in
:issue:24211.)
The :class:mime.text.MIMEText <email.mime.text.MIMEText> constructor now
accepts a :class:charset.Charset <email.charset.Charset> instance.
(Contributed by Claude Paroz and Berker Peksag in :issue:16324.)
The :class:~enum.Enum callable has a new parameter start to
specify the initial number of enum values if only names are provided::
>>> Animal = enum.Enum('Animal', 'cat dog', start=10)
>>> Animal.cat
<Animal.cat: 10>
>>> Animal.dog
<Animal.dog: 11>
(Contributed by Ethan Furman in :issue:21706.)
The :func:~faulthandler.enable, :func:~faulthandler.register,
:func:~faulthandler.dump_traceback and
:func:~faulthandler.dump_traceback_later functions now accept file
descriptors in addition to file-like objects.
(Contributed by Wei Wu in :issue:23566.)
.. _whatsnew-lrucache:
Most of the :func:~functools.lru_cache machinery is now implemented in C, making
it significantly faster. (Contributed by Matt Joiner, Alexey Kachayev, and
Serhiy Storchaka in :issue:14373.)
The :func:~glob.iglob and :func:~glob.glob functions now support recursive
search in subdirectories, using the "**" pattern.
(Contributed by Serhiy Storchaka in :issue:13968.)
The mode argument of the :class:~gzip.GzipFile constructor now
accepts "x" to request exclusive creation.
(Contributed by Tim Heaney in :issue:19222.)
Element comparison in :func:~heapq.merge can now be customized by
passing a :term:key function in a new optional key keyword argument,
and a new optional reverse keyword argument can be used to reverse element
comparison::
>>> import heapq
>>> a = ['9', '777', '55555']
>>> b = ['88', '6666']
>>> list(heapq.merge(a, b, key=len))
['9', '88', '777', '6666', '55555']
>>> list(heapq.merge(reversed(a), reversed(b), key=len, reverse=True))
['55555', '6666', '777', '88', '9']
(Contributed by Raymond Hettinger in :issue:13742.)
A new :class:HTTPStatus <http.HTTPStatus> enum that defines a set of
HTTP status codes, reason phrases and long descriptions written in English.
(Contributed by Demian Brecht in :issue:21793.)
:meth:HTTPConnection.getresponse() <http.client.HTTPConnection.getresponse>
now raises a :exc:~http.client.RemoteDisconnected exception when a
remote server connection is closed unexpectedly. Additionally, if a
:exc:ConnectionError (of which RemoteDisconnected
is a subclass) is raised, the client socket is now closed automatically,
and will reconnect on the next request::
import http.client
conn = http.client.HTTPConnection('www.python.org')
for retries in range(3):
try:
conn.request('GET', '/')
resp = conn.getresponse()
except http.client.RemoteDisconnected:
pass
(Contributed by Martin Panter in :issue:3566.)
Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release. See
:file:Lib/idlelib/NEWS.txt for a cumulative list of changes since 3.4.0,
as well as changes made in future 3.5.x releases. This file is also available
from the IDLE :menuselection:Help --> About IDLE dialog.
The :class:~imaplib.IMAP4 class now supports the :term:context manager protocol.
When used in a :keyword:with statement, the IMAP4 LOGOUT
command will be called automatically at the end of the block.
(Contributed by Tarek Ziadé and Serhiy Storchaka in :issue:4972.)
The :mod:imaplib module now supports :rfc:5161 (ENABLE Extension)
and :rfc:6855 (UTF-8 Support) via the :meth:IMAP4.enable() <imaplib.IMAP4.enable>
method. A new :attr:IMAP4.utf8_enabled <imaplib.IMAP4.utf8_enabled>
attribute tracks whether or not :rfc:6855 support is enabled.
(Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in
:issue:21800.)
The :mod:imaplib module now automatically encodes non-ASCII string usernames
and passwords using UTF-8, as recommended by the RFCs. (Contributed by Milan
Oberkirch in :issue:21800.)
The :func:~imghdr.what function now recognizes the
OpenEXR <http://www.openexr.com>_ format
(contributed by Martin Vignali and Claudiu Popa in :issue:20295),
and the WebP <https://en.wikipedia.org/wiki/WebP>_ format
(contributed by Fabrice Aneche and Claudiu Popa in :issue:20197.)
The :class:util.LazyLoader <importlib.util.LazyLoader> class allows for
lazy loading of modules in applications where startup time is important.
(Contributed by Brett Cannon in :issue:17621.)
The :func:abc.InspectLoader.source_to_code() <importlib.abc.InspectLoader.source_to_code>
method is now a static method. This makes it easier to initialize a module
object with code compiled from a string by running
exec(code, module.__dict__).
(Contributed by Brett Cannon in :issue:21156.)
The new :func:util.module_from_spec() <importlib.util.module_from_spec>
function is now the preferred way to create a new module. As opposed to
creating a :class:types.ModuleType instance directly, this new function
will set the various import-controlled attributes based on the passed-in
spec object. (Contributed by Brett Cannon in :issue:20383.)
Both the :class:~inspect.Signature and :class:~inspect.Parameter classes are
now picklable and hashable. (Contributed by Yury Selivanov in :issue:20726
and :issue:20334.)
A new
:meth:BoundArguments.apply_defaults() <inspect.BoundArguments.apply_defaults>
method provides a way to set default values for missing arguments::
>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])
(Contributed by Yury Selivanov in :issue:24190.)
A new class method
:meth:Signature.from_callable() <inspect.Signature.from_callable> makes
subclassing of :class:~inspect.Signature easier. (Contributed
by Yury Selivanov and Eric Snow in :issue:17373.)
The :func:~inspect.signature function now accepts a follow_wrapped
optional keyword argument, which, when set to False, disables automatic
following of __wrapped__ links.
(Contributed by Yury Selivanov in :issue:20691.)
A set of new functions to inspect
:term:coroutine functions <coroutine function> and
:term:coroutine objects <coroutine> has been added:
:func:~inspect.iscoroutine, :func:~inspect.iscoroutinefunction,
:func:~inspect.isawaitable, :func:~inspect.getcoroutinelocals,
and :func:~inspect.getcoroutinestate.
(Contributed by Yury Selivanov in :issue:24017 and :issue:24400.)
The :func:~inspect.stack, :func:~inspect.trace,
:func:~inspect.getouterframes, and :func:~inspect.getinnerframes
functions now return a list of named tuples.
(Contributed by Daniel Shahaf in :issue:16808.)
A new :meth:BufferedIOBase.readinto1() <io.BufferedIOBase.readinto1>
method, that uses at most one call to the underlying raw stream's
:meth:RawIOBase.read() <io.RawIOBase.read> or
:meth:RawIOBase.readinto() <io.RawIOBase.readinto> methods.
(Contributed by Nikolaus Rath in :issue:20578.)
Both the :class:~ipaddress.IPv4Network and :class:~ipaddress.IPv6Network classes
now accept an (address, netmask) tuple argument, so as to easily construct
network objects from existing addresses::
>>> import ipaddress
>>> ipaddress.IPv4Network(('127.0.0.0', 8))
IPv4Network('127.0.0.0/8')
>>> ipaddress.IPv4Network(('127.0.0.0', '255.0.0.0'))
IPv4Network('127.0.0.0/8')
(Contributed by Peter Moody and Antoine Pitrou in :issue:16531.)
A new :attr:~ipaddress.IPv4Network.reverse_pointer attribute for the
:class:~ipaddress.IPv4Network and :class:~ipaddress.IPv6Network classes
returns the name of the reverse DNS PTR record::
>>> import ipaddress
>>> addr = ipaddress.IPv4Address('127.0.0.1')
>>> addr.reverse_pointer
'1.0.0.127.in-addr.arpa'
>>> addr6 = ipaddress.IPv6Address('::1')
>>> addr6.reverse_pointer
'1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa'
(Contributed by Leon Weber in :issue:20480.)
The :mod:json.tool command line interface now preserves the order of keys in
JSON objects passed in input. The new --sort-keys option can be used
to sort the keys alphabetically. (Contributed by Berker Peksag
in :issue:21650.)
JSON decoder now raises :exc:~json.JSONDecodeError instead of
:exc:ValueError to provide better context information about the error.
(Contributed by Serhiy Storchaka in :issue:19361.)
A new :func:~linecache.lazycache function can be used to capture information
about a non-file-based module to permit getting its lines later via
:func:~linecache.getline. This avoids doing I/O until a line is actually
needed, without having to carry the module globals around indefinitely.
(Contributed by Robert Collins in :issue:17911.)
A new :func:~locale.delocalize function can be used to convert a string into
a normalized number string, taking the LC_NUMERIC settings into account::
>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'de_DE.UTF-8')
'de_DE.UTF-8'
>>> locale.delocalize('1.234,56')
'1234.56'
>>> locale.setlocale(locale.LC_NUMERIC, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.delocalize('1,234.56')
'1234.56'
(Contributed by Cédric Krier in :issue:13918.)
All logging methods (:class:~logging.Logger :meth:~logging.Logger.log,
:meth:~logging.Logger.exception, :meth:~logging.Logger.critical,
:meth:~logging.Logger.debug, etc.), now accept exception instances
as an exc_info argument, in addition to boolean values and exception
tuples::
>>> import logging
>>> try:
... 1/0
... except ZeroDivisionError as ex:
... logging.error('exception', exc_info=ex)
ERROR:root:exception
(Contributed by Yury Selivanov in :issue:20537.)
The :class:handlers.HTTPHandler <logging.handlers.HTTPHandler> class now
accepts an optional :class:ssl.SSLContext instance to configure SSL
settings used in an HTTP connection.
(Contributed by Alex Gaynor in :issue:22788.)
The :class:handlers.QueueListener <logging.handlers.QueueListener> class now
takes a respect_handler_level keyword argument which, if set to True,
will pass messages to handlers taking handler levels into account.
(Contributed by Vinay Sajip.)
The :meth:LZMADecompressor.decompress() <lzma.LZMADecompressor.decompress>
method now accepts an optional max_length argument to limit the maximum
size of decompressed data.
(Contributed by Martin Panter in :issue:15955.)
Two new constants have been added to the :mod:math module: :data:~math.inf
and :data:~math.nan. (Contributed by Mark Dickinson in :issue:23185.)
A new function :func:~math.isclose provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in :issue:24270.)
A new :func:~math.gcd function has been added. The :func:fractions.gcd
function is now deprecated. (Contributed by Mark Dickinson and Serhiy
Storchaka in :issue:22486.)
:func:sharedctypes.synchronized() <multiprocessing.sharedctypes.synchronized>
objects now support the :term:context manager protocol.
(Contributed by Charles-François Natali in :issue:21565.)
:func:~operator.attrgetter, :func:~operator.itemgetter,
and :func:~operator.methodcaller objects now support pickling.
(Contributed by Josh Rosenberg and Serhiy Storchaka in :issue:22955.)
New :func:~operator.matmul and :func:~operator.imatmul functions
to perform matrix multiplication.
(Contributed by Benjamin Peterson in :issue:21176.)
The new :func:~os.scandir function returning an iterator of
:class:~os.DirEntry objects has been added. If possible, :func:~os.scandir
extracts file attributes while scanning a directory, removing the need to
perform subsequent system calls to determine file type or attributes, which may
significantly improve performance. (Contributed by Ben Hoyt with the help
of Victor Stinner in :issue:22524.)
On Windows, a new
:attr:stat_result.st_file_attributes <os.stat_result.st_file_attributes>
attribute is now available. It corresponds to the dwFileAttributes member
of the BY_HANDLE_FILE_INFORMATION structure returned by
GetFileInformationByHandle(). (Contributed by Ben Hoyt in :issue:21719.)
The :func:~os.urandom function now uses the getrandom() syscall on Linux 3.17
or newer, and getentropy() on OpenBSD 5.6 and newer, removing the need to
use /dev/urandom and avoiding failures due to potential file descriptor
exhaustion. (Contributed by Victor Stinner in :issue:22181.)
New :func:~os.get_blocking and :func:~os.set_blocking functions allow
getting and setting a file descriptor's blocking mode (:data:~os.O_NONBLOCK.)
(Contributed by Victor Stinner in :issue:22054.)
The :func:~os.truncate and :func:~os.ftruncate functions are now supported
on Windows. (Contributed by Steve Dower in :issue:23668.)
There is a new :func:os.path.commonpath function returning the longest
common sub-path of each passed pathname. Unlike the
:func:os.path.commonprefix function, it always returns a valid
path::
>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'
>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'
(Contributed by Rafik Draoui and Serhiy Storchaka in :issue:10395.)
The new :meth:Path.samefile() <pathlib.Path.samefile> method can be used
to check whether the path points to the same file as another path, which can
be either another :class:~pathlib.Path object, or a string::
>>> import pathlib
>>> p1 = pathlib.Path('/etc/hosts')
>>> p2 = pathlib.Path('/etc/../etc/hosts')
>>> p1.samefile(p2)
True
(Contributed by Vajrasky Kok and Antoine Pitrou in :issue:19775.)
The :meth:Path.mkdir() <pathlib.Path.mkdir> method now accepts a new optional
exist_ok argument to match mkdir -p and :func:os.makedirs
functionality. (Contributed by Berker Peksag in :issue:21539.)
There is a new :meth:Path.expanduser() <pathlib.Path.expanduser> method to
expand ~ and ~user prefixes. (Contributed by Serhiy Storchaka and
Claudiu Popa in :issue:19776.)
A new :meth:Path.home() <pathlib.Path.home> class method can be used to get
a :class:~pathlib.Path instance representing the user’s home
directory.
(Contributed by Victor Salgado and Mayank Tripathi in :issue:19777.)
New :meth:Path.write_text() <pathlib.Path.write_text>,
:meth:Path.read_text() <pathlib.Path.read_text>,
:meth:Path.write_bytes() <pathlib.Path.write_bytes>,
:meth:Path.read_bytes() <pathlib.Path.read_bytes> methods to simplify
read/write operations on files.
The following code snippet will create or rewrite existing file
~/spam42::
>>> import pathlib
>>> p = pathlib.Path('~/spam42')
>>> p.expanduser().write_text('ham')
3
(Contributed by Christopher Welborn in :issue:20218.)
Nested objects, such as unbound methods or nested classes, can now be pickled
using :ref:pickle protocols <pickle-protocols> older than protocol version 4.
Protocol version 4 already supports these cases. (Contributed by Serhiy
Storchaka in :issue:23611.)
A new :meth:POP3.utf8() <poplib.POP3.utf8> command enables :rfc:6856
(Internationalized Email) support, if a POP server supports it.
(Contributed by Milan OberKirch in :issue:21804.)
References and conditional references to groups with fixed length are now allowed in lookbehind assertions::
>>> import re
>>> pat = re.compile(r'(a|b).(?<=\1)c')
>>> pat.match('aac')
<_sre.SRE_Match object; span=(0, 3), match='aac'>
>>> pat.match('bbc')
<_sre.SRE_Match object; span=(0, 3), match='bbc'>
(Contributed by Serhiy Storchaka in :issue:9179.)
The number of capturing groups in regular expressions is no longer limited to
100. (Contributed by Serhiy Storchaka in :issue:22437.)
The :func:~re.sub and :func:~re.subn functions now replace unmatched
groups with empty strings instead of raising an exception.
(Contributed by Serhiy Storchaka in :issue:1519638.)
The :class:re.error exceptions have new attributes,
:attr:~re.error.msg, :attr:~re.error.pattern,
:attr:~re.error.pos, :attr:~re.error.lineno,
and :attr:~re.error.colno, that provide better context
information about the error::
>>> re.compile("""
... (?x)
... .++
... """)
Traceback (most recent call last):
...
sre_constants.error: multiple repeat at position 16 (line 3, column 7)
(Contributed by Serhiy Storchaka in :issue:22578.)
A new :func:~readline.append_history_file function can be used to append
the specified number of trailing elements in history to the given file.
(Contributed by Bruno Cauet in :issue:22940.)
The new :class:~selectors.DevpollSelector supports efficient
/dev/poll polling on Solaris.
(Contributed by Giampaolo Rodola' in :issue:18931.)
The :func:~shutil.move function now accepts a copy_function argument,
allowing, for example, the :func:~shutil.copy function to be used instead of
the default :func:~shutil.copy2 if there is a need to ignore file metadata
when moving.
(Contributed by Claudiu Popa in :issue:19840.)
The :func:~shutil.make_archive function now supports the xztar format.
(Contributed by Serhiy Storchaka in :issue:5411.)
On Windows, the :func:~signal.set_wakeup_fd function now also supports
socket handles. (Contributed by Victor Stinner in :issue:22018.)
Various SIG* constants in the :mod:signal module have been converted into
:mod:Enums <enum>. This allows meaningful names to be printed
during debugging, instead of integer "magic numbers".
(Contributed by Giampaolo Rodola' in :issue:21076.)
Both the :class:~smtpd.SMTPServer and :class:~smtpd.SMTPChannel classes now
accept a decode_data keyword argument to determine if the DATA portion of
the SMTP transaction is decoded using the "utf-8" codec or is instead
provided to the
:meth:SMTPServer.process_message() <smtpd.SMTPServer.process_message>
method as a byte string. The default is True for backward compatibility
reasons, but will change to False in Python 3.6. If decode_data is set
to False, the process_message method must be prepared to accept keyword
arguments.
(Contributed by Maciej Szulik in :issue:19662.)
The :class:~smtpd.SMTPServer class now advertises the 8BITMIME extension
(:rfc:6152) if decode_data has been set True. If the client
specifies BODY=8BITMIME on the MAIL command, it is passed to
:meth:SMTPServer.process_message() <smtpd.SMTPServer.process_message>
via the mail_options keyword.
(Contributed by Milan Oberkirch and R. David Murray in :issue:21795.)
The :class:~smtpd.SMTPServer class now also supports the SMTPUTF8
extension (:rfc:6531: Internationalized Email). If the client specified
SMTPUTF8 BODY=8BITMIME on the MAIL command, they are passed to
:meth:SMTPServer.process_message() <smtpd.SMTPServer.process_message>
via the mail_options keyword. It is the responsibility of the
process_message method to correctly handle the SMTPUTF8 data.
(Contributed by Milan Oberkirch in :issue:21725.)
It is now possible to provide, directly or via name resolution, IPv6
addresses in the :class:~smtpd.SMTPServer constructor, and have it
successfully connect. (Contributed by Milan Oberkirch in :issue:14758.)
A new :meth:SMTP.auth() <smtplib.SMTP.auth> method provides a convenient way to
implement custom authentication mechanisms. (Contributed by Milan
Oberkirch in :issue:15014.)
The :meth:SMTP.set_debuglevel() <smtplib.SMTP.set_debuglevel> method now
accepts an additional debuglevel (2), which enables timestamps in debug
messages. (Contributed by Gavin Chappell and Maciej Szulik in :issue:16914.)
Both the :meth:SMTP.sendmail() <smtplib.SMTP.sendmail> and
:meth:SMTP.send_message() <smtplib.SMTP.send_message> methods now
support :rfc:6531 (SMTPUTF8).
(Contributed by Milan Oberkirch and R. David Murray in :issue:22027.)
The :func:~sndhdr.what and :func:~sndhdr.whathdr functions now return
a :func:~collections.namedtuple. (Contributed by Claudiu Popa in
:issue:18615.)
Functions with timeouts now use a monotonic clock, instead of a system clock.
(Contributed by Victor Stinner in :issue:22043.)
A new :meth:socket.sendfile() <socket.socket.sendfile> method allows
sending a file over a socket by using the high-performance :func:os.sendfile
function on UNIX, resulting in uploads being from 2 to 3 times faster than when
using plain :meth:socket.send() <socket.socket.send>.
(Contributed by Giampaolo Rodola' in :issue:17552.)
The :meth:socket.sendall() <socket.socket.sendall> method no longer resets the
socket timeout every time bytes are received or sent. The socket timeout is
now the maximum total duration to send all data.
(Contributed by Victor Stinner in :issue:23853.)
The backlog argument of the :meth:socket.listen() <socket.socket.listen>
method is now optional. By default it is set to
:data:SOMAXCONN <socket.SOMAXCONN> or to 128, whichever is less.
(Contributed by Charles-François Natali in :issue:21455.)
.. _whatsnew-sslmemorybio:
Memory BIO Support
(Contributed by Geert Jansen in :issue:`21965`.)
The new :class:`~ssl.SSLObject` class has been added to provide SSL protocol
support for cases when the network I/O capabilities of :class:`~ssl.SSLSocket`
are not necessary or are suboptimal. ``SSLObject`` represents
an SSL protocol instance, but does not implement any network I/O methods, and
instead provides a memory buffer interface. The new :class:`~ssl.MemoryBIO`
class can be used to pass data between Python and an SSL protocol instance.
The memory BIO SSL support is primarily intended to be used in frameworks
implementing asynchronous I/O for which :class:`~ssl.SSLSocket`'s readiness
model ("select/poll") is inefficient.
A new :meth:`SSLContext.wrap_bio() <ssl.SSLContext.wrap_bio>` method can be used
to create a new ``SSLObject`` instance.
Application-Layer Protocol Negotiation Support
(Contributed by Benjamin Peterson in :issue:20188.)
Where OpenSSL support is present, the :mod:ssl module now implements
the Application-Layer Protocol Negotiation TLS extension as described
in :rfc:7301.
The new :meth:SSLContext.set_alpn_protocols() <ssl.SSLContext.set_alpn_protocols>
can be used to specify which protocols a socket should advertise during
the TLS handshake.
The new
:meth:SSLSocket.selected_alpn_protocol() <ssl.SSLSocket.selected_alpn_protocol>
returns the protocol that was selected during the TLS handshake.
The :data:~ssl.HAS_ALPN flag indicates whether ALPN support is present.
Other Changes
There is a new :meth:`SSLSocket.version() <ssl.SSLSocket.version>` method to
query the actual protocol version in use.
(Contributed by Antoine Pitrou in :issue:`20421`.)
The :class:`~ssl.SSLSocket` class now implements
a :meth:`SSLSocket.sendfile() <ssl.SSLSocket.sendfile>` method.
(Contributed by Giampaolo Rodola' in :issue:`17552`.)
The :meth:`SSLSocket.send() <ssl.SSLSocket.send>` method now raises either
the :exc:`ssl.SSLWantReadError` or :exc:`ssl.SSLWantWriteError` exception on a
non-blocking socket if the operation would block. Previously, it would return
``0``. (Contributed by Nikolaus Rath in :issue:`20951`.)
The :func:`~ssl.cert_time_to_seconds` function now interprets the input time
as UTC and not as local time, per :rfc:`5280`. Additionally, the return
value is always an :class:`int`. (Contributed by Akira Li in :issue:`19940`.)
New :meth:`SSLObject.shared_ciphers() <ssl.SSLObject.shared_ciphers>` and
:meth:`SSLSocket.shared_ciphers() <ssl.SSLSocket.shared_ciphers>` methods return
the list of ciphers sent by the client during the handshake.
(Contributed by Benjamin Peterson in :issue:`23186`.)
The :meth:`SSLSocket.do_handshake() <ssl.SSLSocket.do_handshake>`,
:meth:`SSLSocket.read() <ssl.SSLSocket.read>`,
:meth:`SSLSocket.shutdown() <ssl.SSLSocket.shutdown>`, and
:meth:`SSLSocket.write() <ssl.SSLSocket.write>` methods of the :class:`~ssl.SSLSocket`
class no longer reset the socket timeout every time bytes are received or sent.
The socket timeout is now the maximum total duration of the method.
(Contributed by Victor Stinner in :issue:`23853`.)
The :func:`~ssl.match_hostname` function now supports matching of IP addresses.
(Contributed by Antoine Pitrou in :issue:`23239`.)
sqlite3
-------
The :class:`~sqlite3.Row` class now fully supports the sequence protocol,
in particular :func:`reversed` iteration and slice indexing.
(Contributed by Claudiu Popa in :issue:`10203`; by Lucas Sinclair,
Jessica McKellar, and Serhiy Storchaka in :issue:`13583`.)
.. _whatsnew-subprocess:
subprocess
----------
The new :func:`~subprocess.run` function has been added.
It runs the specified command and returns a
:class:`~subprocess.CompletedProcess` object, which describes a finished
process. The new API is more consistent and is the recommended approach
to invoking subprocesses in Python code that does not need to maintain
compatibility with earlier Python versions.
(Contributed by Thomas Kluyver in :issue:`23342`.)
Examples::
>>> subprocess.run(["ls", "-l"]) # doesn't capture output
CompletedProcess(args=['ls', '-l'], returncode=0)
>>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1
>>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')
sys
---
A new :func:`~sys.set_coroutine_wrapper` function allows setting a global
hook that will be called whenever a :term:`coroutine object <coroutine>`
is created by an :keyword:`async def` function. A corresponding
:func:`~sys.get_coroutine_wrapper` can be used to obtain a currently set
wrapper. Both functions are :term:`provisional <provisional api>`,
and are intended for debugging purposes only. (Contributed by Yury Selivanov
in :issue:`24017`.)
A new :func:`~sys.is_finalizing` function can be used to check if the Python
interpreter is :term:`shutting down <interpreter shutdown>`.
(Contributed by Antoine Pitrou in :issue:`22696`.)
sysconfig
---------
The name of the user scripts directory on Windows now includes the first
two components of the Python version. (Contributed by Paul Moore
in :issue:`23437`.)
tarfile
-------
The *mode* argument of the :func:`~tarfile.open` function now accepts ``"x"``
to request exclusive creation. (Contributed by Berker Peksag in :issue:`21717`.)
The :meth:`TarFile.extractall() <tarfile.TarFile.extractall>` and
:meth:`TarFile.extract() <tarfile.TarFile.extract>` methods now take a keyword
argument *numeric_owner*. If set to ``True``, the extracted files and
directories will be owned by the numeric ``uid`` and ``gid`` from the tarfile.
If set to ``False`` (the default, and the behavior in versions prior to 3.5),
they will be owned by the named user and group in the tarfile.
(Contributed by Michael Vogt and Eric Smith in :issue:`23193`.)
The :meth:`TarFile.list() <tarfile.TarFile.list>` now accepts an optional
*members* keyword argument that can be set to a subset of the list returned
by :meth:`TarFile.getmembers() <tarfile.TarFile.getmembers>`.
(Contributed by Serhiy Storchaka in :issue:`21549`.)
threading
---------
Both the :meth:`Lock.acquire() <threading.Lock.acquire>` and
:meth:`RLock.acquire() <threading.RLock.acquire>` methods
now use a monotonic clock for timeout management.
(Contributed by Victor Stinner in :issue:`22043`.)
time
----
The :func:`~time.monotonic` function is now always available.
(Contributed by Victor Stinner in :issue:`22043`.)
timeit
------
A new command line option ``-u`` or :samp:`--unit={U}` can be used to specify the time
unit for the timer output. Supported options are ``usec``, ``msec``,
or ``sec``. (Contributed by Julian Gindi in :issue:`18983`.)
The :func:`~timeit.timeit` function has a new *globals* parameter for
specifying the namespace in which the code will be running.
(Contributed by Ben Roberts in :issue:`2527`.)
tkinter
-------
The :mod:`tkinter._fix` module used for setting up the Tcl/Tk environment
on Windows has been replaced by a private function in the :mod:`_tkinter`
module which makes no permanent changes to environment variables.
(Contributed by Zachary Ware in :issue:`20035`.)
.. _whatsnew-traceback:
traceback
---------
New :func:`~traceback.walk_stack` and :func:`~traceback.walk_tb`
functions to conveniently traverse frame and traceback objects.
(Contributed by Robert Collins in :issue:`17911`.)
New lightweight classes: :class:`~traceback.TracebackException`,
:class:`~traceback.StackSummary`, and :class:`~traceback.FrameSummary`.
(Contributed by Robert Collins in :issue:`17911`.)
Both the :func:`~traceback.print_tb` and :func:`~traceback.print_stack` functions
now support negative values for the *limit* argument.
(Contributed by Dmitry Kazakov in :issue:`22619`.)
types
-----
A new :func:`~types.coroutine` function to transform
:term:`generator <generator iterator>` and
:class:`generator-like <collections.abc.Generator>` objects into
:term:`awaitables <awaitable>`.
(Contributed by Yury Selivanov in :issue:`24017`.)
A new type called :class:`~types.CoroutineType`, which is used for
:term:`coroutine` objects created by :keyword:`async def` functions.
(Contributed by Yury Selivanov in :issue:`24400`.)
unicodedata
-----------
The :mod:`unicodedata` module now uses data from `Unicode 8.0.0
<http://unicode.org/versions/Unicode8.0.0/>`_.
unittest
--------
The :meth:`TestLoader.loadTestsFromModule() <unittest.TestLoader.loadTestsFromModule>`
method now accepts a keyword-only argument *pattern* which is passed to
``load_tests`` as the third argument. Found packages are now checked for
``load_tests`` regardless of whether their path matches *pattern*, because it
is impossible for a package name to match the default pattern.
(Contributed by Robert Collins and Barry A. Warsaw in :issue:`16662`.)
Unittest discovery errors now are exposed in the
:data:`TestLoader.errors <unittest.TestLoader.errors>` attribute of the
:class:`~unittest.TestLoader` instance.
(Contributed by Robert Collins in :issue:`19746`.)
A new command line option ``--locals`` to show local variables in
tracebacks. (Contributed by Robert Collins in :issue:`22936`.)
unittest.mock
-------------
The :class:`~unittest.mock.Mock` class has the following improvements:
* The class constructor has a new *unsafe* parameter, which causes mock
objects to raise :exc:`AttributeError` on attribute names starting
with ``"assert"``.
(Contributed by Kushal Das in :issue:`21238`.)
* A new :meth:`Mock.assert_not_called() <unittest.mock.Mock.assert_not_called>`
method to check if the mock object was called.
(Contributed by Kushal Das in :issue:`21262`.)
The :class:`~unittest.mock.MagicMock` class now supports :meth:`__truediv__`,
:meth:`__divmod__` and :meth:`__matmul__` operators.
(Contributed by Johannes Baiter in :issue:`20968`, and Håkan Lövdahl
in :issue:`23581` and :issue:`23568`.)
It is no longer necessary to explicitly pass ``create=True`` to the
:func:`~unittest.mock.patch` function when patching builtin names.
(Contributed by Kushal Das in :issue:`17660`.)
urllib
------
A new
:class:`request.HTTPPasswordMgrWithPriorAuth <urllib.request.HTTPPasswordMgrWithPriorAuth>`
class allows HTTP Basic Authentication credentials to be managed so as to
eliminate unnecessary ``401`` response handling, or to unconditionally send
credentials on the first request in order to communicate with servers that
return a ``404`` response instead of a ``401`` if the ``Authorization`` header
is not sent. (Contributed by Matej Cepl in :issue:`19494` and Akshit Khurana in
:issue:`7159`.)
A new *quote_via* argument for the
:func:`parse.urlencode() <urllib.parse.urlencode>`
function provides a way to control the encoding of query parts if needed.
(Contributed by Samwyse and Arnon Yaari in :issue:`13866`.)
The :func:`request.urlopen() <urllib.request.urlopen>` function accepts an
:class:`ssl.SSLContext` object as a *context* argument, which will be used for
the HTTPS connection. (Contributed by Alex Gaynor in :issue:`22366`.)
The :func:`parse.urljoin() <urllib.parse.urljoin>` was updated to use the
:rfc:`3986` semantics for the resolution of relative URLs, rather than
:rfc:`1808` and :rfc:`2396`.
(Contributed by Demian Brecht and Senthil Kumaran in :issue:`22118`.)
wsgiref
-------
The *headers* argument of the :class:`headers.Headers <wsgiref.headers.Headers>`
class constructor is now optional.
(Contributed by Pablo Torres Navarrete and SilentGhost in :issue:`5800`.)
xmlrpc
------
The :class:`client.ServerProxy <xmlrpc.client.ServerProxy>` class now supports
the :term:`context manager` protocol.
(Contributed by Claudiu Popa in :issue:`20627`.)
The :class:`client.ServerProxy <xmlrpc.client.ServerProxy>` constructor now accepts
an optional :class:`ssl.SSLContext` instance.
(Contributed by Alex Gaynor in :issue:`22960`.)
xml.sax
-------
SAX parsers now support a character stream of the
:class:`xmlreader.InputSource <xml.sax.xmlreader.InputSource>` object.
(Contributed by Serhiy Storchaka in :issue:`2175`.)
:func:`~xml.sax.parseString` now accepts a :class:`str` instance.
(Contributed by Serhiy Storchaka in :issue:`10590`.)
zipfile
-------
ZIP output can now be written to unseekable streams.
(Contributed by Serhiy Storchaka in :issue:`23252`.)
The *mode* argument of :meth:`ZipFile.open() <zipfile.ZipFile.open>` method now
accepts ``"x"`` to request exclusive creation.
(Contributed by Serhiy Storchaka in :issue:`21717`.)
Other module-level changes
==========================
Many functions in the :mod:`mmap`, :mod:`ossaudiodev`, :mod:`socket`,
:mod:`ssl`, and :mod:`codecs` modules now accept writable
:term:`bytes-like objects <bytes-like object>`.
(Contributed by Serhiy Storchaka in :issue:`23001`.)
Optimizations
=============
The :func:`os.walk` function has been sped up by 3 to 5 times on POSIX systems,
and by 7 to 20 times on Windows. This was done using the new :func:`os.scandir`
function, which exposes file information from the underlying ``readdir`` or
``FindFirstFile``/``FindNextFile`` system calls. (Contributed by
Ben Hoyt with help from Victor Stinner in :issue:`23605`.)
Construction of ``bytes(int)`` (filled by zero bytes) is faster and uses less
memory for large objects. ``calloc()`` is used instead of ``malloc()`` to
allocate memory for these objects.
(Contributed by Victor Stinner in :issue:`21233`.)
Some operations on :mod:`ipaddress` :class:`~ipaddress.IPv4Network` and
:class:`~ipaddress.IPv6Network` have been massively sped up, such as
:meth:`~ipaddress.IPv4Network.subnets`, :meth:`~ipaddress.IPv4Network.supernet`,
:func:`~ipaddress.summarize_address_range`, :func:`~ipaddress.collapse_addresses`.
The speed up can range from 3 to 15 times.
(Contributed by Antoine Pitrou, Michel Albert, and Markus in
:issue:`21486`, :issue:`21487`, :issue:`20826`, :issue:`23266`.)
Pickling of :mod:`ipaddress` objects was optimized to produce significantly
smaller output. (Contributed by Serhiy Storchaka in :issue:`23133`.)
Many operations on :class:`io.BytesIO` are now 50% to 100% faster.
(Contributed by Serhiy Storchaka in :issue:`15381` and David Wilson in
:issue:`22003`.)
The :func:`marshal.dumps` function is now faster: 65--85% with versions 3
and 4, 20--25% with versions 0 to 2 on typical data, and up to 5 times in
best cases.
(Contributed by Serhiy Storchaka in :issue:`20416` and :issue:`23344`.)
The UTF-32 encoder is now 3 to 7 times faster.
(Contributed by Serhiy Storchaka in :issue:`15027`.)
Regular expressions are now parsed up to 10% faster.
(Contributed by Serhiy Storchaka in :issue:`19380`.)
The :func:`json.dumps` function was optimized to run with
``ensure_ascii=False`` as fast as with ``ensure_ascii=True``.
(Contributed by Naoki Inada in :issue:`23206`.)
The :c:func:`PyObject_IsInstance` and :c:func:`PyObject_IsSubclass`
functions have been sped up in the common case that the second argument
has :class:`type` as its metaclass.
(Contributed Georg Brandl by in :issue:`22540`.)
Method caching was slightly improved, yielding up to 5% performance
improvement in some benchmarks.
(Contributed by Antoine Pitrou in :issue:`22847`.)
Objects from the :mod:`random` module now use 50% less memory on 64-bit
builds. (Contributed by Serhiy Storchaka in :issue:`23488`.)
The :func:`property` getter calls are up to 25% faster.
(Contributed by Joe Jevnik in :issue:`23910`.)
Instantiation of :class:`fractions.Fraction` is now up to 30% faster.
(Contributed by Stefan Behnel in :issue:`22464`.)
String methods :meth:`~str.find`, :meth:`~str.rfind`, :meth:`~str.split`,
:meth:`~str.partition` and the :keyword:`in` string operator are now significantly
faster for searching 1-character substrings.
(Contributed by Serhiy Storchaka in :issue:`23573`.)
Build and C API Changes
=======================
New ``calloc`` functions were added:
* :c:func:`PyMem_RawCalloc`,
* :c:func:`PyMem_Calloc`,
* :c:func:`PyObject_Calloc`.
(Contributed by Victor Stinner in :issue:`21233`.)
New encoding/decoding helper functions:
* :c:func:`Py_DecodeLocale` (replaced ``_Py_char2wchar()``),
* :c:func:`Py_EncodeLocale` (replaced ``_Py_wchar2char()``).
(Contributed by Victor Stinner in :issue:`18395`.)
A new :c:func:`PyCodec_NameReplaceErrors` function to replace the unicode
encode error with ``\N{...}`` escapes.
(Contributed by Serhiy Storchaka in :issue:`19676`.)
A new :c:func:`PyErr_FormatV` function similar to :c:func:`PyErr_Format`,
but accepts a ``va_list`` argument.
(Contributed by Antoine Pitrou in :issue:`18711`.)
A new :c:data:`PyExc_RecursionError` exception.
(Contributed by Georg Brandl in :issue:`19235`.)
New :c:func:`PyModule_FromDefAndSpec`, :c:func:`PyModule_FromDefAndSpec2`,
and :c:func:`PyModule_ExecDef` functions introduced by :pep:`489` --
multi-phase extension module initialization.
(Contributed by Petr Viktorin in :issue:`24268`.)
New :c:func:`PyNumber_MatrixMultiply` and
:c:func:`PyNumber_InPlaceMatrixMultiply` functions to perform matrix
multiplication.
(Contributed by Benjamin Peterson in :issue:`21176`. See also :pep:`465`
for details.)
The :c:member:`PyTypeObject.tp_finalize` slot is now part of the stable ABI.
Windows builds now require Microsoft Visual C++ 14.0, which
is available as part of `Visual Studio 2015 <https://www.visualstudio.com/>`_.
Extension modules now include a platform information tag in their filename on
some platforms (the tag is optional, and CPython will import extensions without
it, although if the tag is present and mismatched, the extension won't be
loaded):
* On Linux, extension module filenames end with
``.cpython-<major><minor>m-<architecture>-<os>.pyd``:
* ``<major>`` is the major number of the Python version;
for Python 3.5 this is ``3``.
* ``<minor>`` is the minor number of the Python version;
for Python 3.5 this is ``5``.
* ``<architecture>`` is the hardware architecture the extension module
was built to run on. It's most commonly either ``i386`` for 32-bit Intel
platforms or ``x86_64`` for 64-bit Intel (and AMD) platforms.
* ``<os>`` is always ``linux-gnu``, except for extensions built to
talk to the 32-bit ABI on 64-bit platforms, in which case it is
``linux-gnu32`` (and ``<architecture>`` will be ``x86_64``).
* On Windows, extension module filenames end with
``<debug>.cp<major><minor>-<platform>.pyd``:
* ``<major>`` is the major number of the Python version;
for Python 3.5 this is ``3``.
* ``<minor>`` is the minor number of the Python version;
for Python 3.5 this is ``5``.
* ``<platform>`` is the platform the extension module was built for,
either ``win32`` for Win32, ``win_amd64`` for Win64, ``win_ia64`` for
Windows Itanium 64, and ``win_arm`` for Windows on ARM.
* If built in debug mode, ``<debug>`` will be ``_d``,
otherwise it will be blank.
* On OS X platforms, extension module filenames now end with ``-darwin.so``.
* On all other platforms, extension module filenames are the same as they were
with Python 3.4.
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.
Deprecated Python Behavior
--------------------------
Raising the :exc:`StopIteration` exception inside a generator will now generate a silent
:exc:`PendingDeprecationWarning`, which will become a non-silent deprecation
warning in Python 3.6 and will trigger a :exc:`RuntimeError` in Python 3.7.
See :ref:`PEP 479: Change StopIteration handling inside generators <whatsnew-pep-479>`
for details.
Unsupported Operating Systems
-----------------------------
Windows XP is no longer supported by Microsoft, thus, per :PEP:`11`, CPython
3.5 is no longer officially supported on this OS.
Deprecated Python modules, functions and methods
------------------------------------------------
The :mod:`formatter` module has now graduated to full deprecation and is still
slated for removal in Python 3.6.
The :func:`asyncio.async` function is deprecated in favor of
:func:`~asyncio.ensure_future`.
The :mod:`smtpd` module has in the past always decoded the DATA portion of
email messages using the ``utf-8`` codec. This can now be controlled by the
new *decode_data* keyword to :class:`~smtpd.SMTPServer`. The default value is
``True``, but this default is deprecated. Specify the *decode_data* keyword
with an appropriate value to avoid the deprecation warning.
Directly assigning values to the :attr:`~http.cookies.Morsel.key`,
:attr:`~http.cookies.Morsel.value` and
:attr:`~http.cookies.Morsel.coded_value` of :class:`http.cookies.Morsel`
objects is deprecated. Use the :meth:`~http.cookies.Morsel.set` method
instead. In addition, the undocumented *LegalChars* parameter of
:meth:`~http.cookies.Morsel.set` is deprecated, and is now ignored.
Passing a format string as keyword argument *format_string* to the
:meth:`~string.Formatter.format` method of the :class:`string.Formatter`
class has been deprecated.
(Contributed by Serhiy Storchaka in :issue:`23671`.)
The :func:`platform.dist` and :func:`platform.linux_distribution` functions
are now deprecated. Linux distributions use too many different ways of
describing themselves, so the functionality is left to a package.
(Contributed by Vajrasky Kok and Berker Peksag in :issue:`1322`.)
The previously undocumented ``from_function`` and ``from_builtin`` methods of
:class:`inspect.Signature` are deprecated. Use the new
:meth:`Signature.from_callable() <inspect.Signature.from_callable>`
method instead. (Contributed by Yury Selivanov in :issue:`24248`.)
The :func:`inspect.getargspec` function is deprecated and scheduled to be
removed in Python 3.6. (See :issue:`20438` for details.)
The :mod:`inspect` :func:`~inspect.getfullargspec`,
:func:`~inspect.getcallargs`, and :func:`~inspect.formatargspec` functions are
deprecated in favor of the :func:`inspect.signature` API. (Contributed by Yury
Selivanov in :issue:`20438`.)
:func:`~inspect.getargvalues` and :func:`~inspect.formatargvalues` functions
were inadvertently marked as deprecated with the release of Python 3.5.0.
Use of :const:`re.LOCALE` flag with str patterns or :const:`re.ASCII` is now
deprecated. (Contributed by Serhiy Storchaka in :issue:`22407`.)
Use of unrecognized special sequences consisting of ``'\'`` and an ASCII letter
in regular expression patterns and replacement patterns now raises a
deprecation warning and will be forbidden in Python 3.6.
(Contributed by Serhiy Storchaka in :issue:`23622`.)
The undocumented and unofficial *use_load_tests* default argument of the
:meth:`unittest.TestLoader.loadTestsFromModule` method now is
deprecated and ignored.
(Contributed by Robert Collins and Barry A. Warsaw in :issue:`16662`.)
Removed
=======
API and Feature Removals
------------------------
The following obsolete and previously deprecated APIs and features have been
removed:
* The ``__version__`` attribute has been dropped from the email package. The
email code hasn't been shipped separately from the stdlib for a long time,
and the ``__version__`` string was not updated in the last few releases.
* The internal ``Netrc`` class in the :mod:`ftplib` module was deprecated in
3.4, and has now been removed.
(Contributed by Matt Chaput in :issue:`6623`.)
* The concept of ``.pyo`` files has been removed.
* The JoinableQueue class in the provisional :mod:`asyncio` module was
deprecated in 3.4.4 and is now removed.
(Contributed by A. Jesse Jiryu Davis in :issue:`23464`.)
Porting to Python 3.5
=====================
This section lists previously described changes and other bugfixes
that may require changes to your code.
Changes in Python behavior
--------------------------
* Due to an oversight, earlier Python versions erroneously accepted the
following syntax::
f(1 for x in [1], *args)
f(1 for x in [1], **kwargs)
Python 3.5 now correctly raises a :exc:`SyntaxError`, as generator
expressions must be put in parentheses if not a sole argument to a function.
Changes in the Python API
-------------------------
* :pep:`475`: System calls are now retried when interrupted by a signal instead
of raising :exc:`InterruptedError` if the Python signal handler does not
raise an exception.
* Before Python 3.5, a :class:`datetime.time` object was considered to be false
if it represented midnight in UTC. This behavior was considered obscure and
error-prone and has been removed in Python 3.5. See :issue:`13936` for full
details.
* The :meth:`ssl.SSLSocket.send()` method now raises either
:exc:`ssl.SSLWantReadError` or :exc:`ssl.SSLWantWriteError`
on a non-blocking socket if the operation would block. Previously,
it would return ``0``. (Contributed by Nikolaus Rath in :issue:`20951`.)
* The ``__name__`` attribute of generators is now set from the function name,
instead of being set from the code name. Use ``gen.gi_code.co_name`` to
retrieve the code name. Generators also have a new ``__qualname__``
attribute, the qualified name, which is now used for the representation
of a generator (``repr(gen)``).
(Contributed by Victor Stinner in :issue:`21205`.)
* The deprecated "strict" mode and argument of :class:`~html.parser.HTMLParser`,
:meth:`HTMLParser.error`, and the :exc:`HTMLParserError` exception have been
removed. (Contributed by Ezio Melotti in :issue:`15114`.)
The *convert_charrefs* argument of :class:`~html.parser.HTMLParser` is
now ``True`` by default. (Contributed by Berker Peksag in :issue:`21047`.)
* Although it is not formally part of the API, it is worth noting for porting
purposes (ie: fixing tests) that error messages that were previously of the
form "'sometype' does not support the buffer protocol" are now of the form "a
:term:`bytes-like object` is required, not 'sometype'".
(Contributed by Ezio Melotti in :issue:`16518`.)
* If the current directory is set to a directory that no longer exists then
:exc:`FileNotFoundError` will no longer be raised and instead
:meth:`~importlib.machinery.FileFinder.find_spec` will return ``None``
**without** caching ``None`` in :data:`sys.path_importer_cache`, which is
different than the typical case (:issue:`22834`).
* HTTP status code and messages from :mod:`http.client` and :mod:`http.server`
were refactored into a common :class:`~http.HTTPStatus` enum. The values in
:mod:`http.client` and :mod:`http.server` remain available for backwards
compatibility. (Contributed by Demian Brecht in :issue:`21793`.)
* When an import loader defines :meth:`importlib.machinery.Loader.exec_module`
it is now expected to also define
:meth:`~importlib.machinery.Loader.create_module` (raises a
:exc:`DeprecationWarning` now, will be an error in Python 3.6). If the loader
inherits from :class:`importlib.abc.Loader` then there is nothing to do, else
simply define :meth:`~importlib.machinery.Loader.create_module` to return
``None``. (Contributed by Brett Cannon in :issue:`23014`.)
* The :func:`re.split` function always ignored empty pattern matches, so the
``"x*"`` pattern worked the same as ``"x+"``, and the ``"\b"`` pattern never
worked. Now :func:`re.split` raises a warning if the pattern could match
an empty string. For compatibility, use patterns that never match an empty
string (e.g. ``"x+"`` instead of ``"x*"``). Patterns that could only match
an empty string (such as ``"\b"``) now raise an error.
(Contributed by Serhiy Storchaka in :issue:`22818`.)
* The :class:`http.cookies.Morsel` dict-like interface has been made self
consistent: morsel comparison now takes the :attr:`~http.cookies.Morsel.key`
and :attr:`~http.cookies.Morsel.value` into account,
:meth:`~http.cookies.Morsel.copy` now results in a
:class:`~http.cookies.Morsel` instance rather than a :class:`dict`, and
:meth:`~http.cookies.Morsel.update` will now raise an exception if any of the
keys in the update dictionary are invalid. In addition, the undocumented
*LegalChars* parameter of :func:`~http.cookies.Morsel.set` is deprecated and
is now ignored. (Contributed by Demian Brecht in :issue:`2211`.)
* :pep:`488` has removed ``.pyo`` files from Python and introduced the optional
``opt-`` tag in ``.pyc`` file names. The
:func:`importlib.util.cache_from_source` has gained an *optimization*
parameter to help control the ``opt-`` tag. Because of this, the
*debug_override* parameter of the function is now deprecated. `.pyo` files
are also no longer supported as a file argument to the Python interpreter and
thus serve no purpose when distributed on their own (i.e. sourceless code
distribution). Due to the fact that the magic number for bytecode has changed
in Python 3.5, all old `.pyo` files from previous versions of Python are
invalid regardless of this PEP.
* The :mod:`socket` module now exports the :data:`~socket.CAN_RAW_FD_FRAMES`
constant on linux 3.6 and greater.
* The :func:`ssl.cert_time_to_seconds` function now interprets the input time
as UTC and not as local time, per :rfc:`5280`. Additionally, the return
value is always an :class:`int`. (Contributed by Akira Li in :issue:`19940`.)
* The ``pygettext.py`` Tool now uses the standard +NNNN format for timezones in
the POT-Creation-Date header.
* The :mod:`smtplib` module now uses :data:`sys.stderr` instead of the previous
module-level :data:`stderr` variable for debug output. If your (test)
program depends on patching the module-level variable to capture the debug
output, you will need to update it to capture sys.stderr instead.
* The :meth:`str.startswith` and :meth:`str.endswith` methods no longer return
``True`` when finding the empty string and the indexes are completely out of
range. (Contributed by Serhiy Storchaka in :issue:`24284`.)
* The :func:`inspect.getdoc` function now returns documentation strings
inherited from base classes. Documentation strings no longer need to be
duplicated if the inherited documentation is appropriate. To suppress an
inherited string, an empty string must be specified (or the documentation
may be filled in). This change affects the output of the :mod:`pydoc`
module and the :func:`help` function.
(Contributed by Serhiy Storchaka in :issue:`15582`.)
* Nested :func:`functools.partial` calls are now flattened. If you were
relying on the previous behavior, you can now either add an attribute to a
:func:`functools.partial` object or you can create a subclass of
:func:`functools.partial`.
(Contributed by Alexander Belopolsky in :issue:`7830`.)
Changes in the C API
--------------------
* The undocumented :c:member:`~PyMemoryViewObject.format` member of the
(non-public) :c:type:`PyMemoryViewObject` structure has been removed.
All extensions relying on the relevant parts in ``memoryobject.h``
must be rebuilt.
* The :c:type:`PyMemAllocator` structure was renamed to
:c:type:`PyMemAllocatorEx` and a new ``calloc`` field was added.
* Removed non-documented macro :c:macro:`PyObject_REPR` which leaked references.
Use format character ``%R`` in :c:func:`PyUnicode_FromFormat`-like functions
to format the :func:`repr` of the object.
(Contributed by Serhiy Storchaka in :issue:`22453`.)
* Because the lack of the :attr:`__module__` attribute breaks pickling and
introspection, a deprecation warning is now raised for builtin types without
the :attr:`__module__` attribute. This would be an AttributeError in
the future.
(Contributed by Serhiy Storchaka in :issue:`20204`.)
* As part of the :pep:`492` implementation, the ``tp_reserved`` slot of
:c:type:`PyTypeObject` was replaced with a
:c:member:`tp_as_async` slot. Refer to :ref:`coro-objects` for
new types, structures and functions.
Notable changes in Python 3.5.4
===============================
New ``make regen-all`` build target
-----------------------------------
To simplify cross-compilation, and to ensure that CPython can reliably be
compiled without requiring an existing version of Python to already be
available, the autotools-based build system no longer attempts to implicitly
recompile generated files based on file modification times.
Instead, a new ``make regen-all`` command has been added to force regeneration
of these files when desired (e.g. after an initial version of Python has
already been built based on the pregenerated versions).
More selective regeneration targets are also defined - see
:source:`Makefile.pre.in` for details.
(Contributed by Victor Stinner in :issue:`23404`.)
.. versionadded:: 3.5.4
Removal of ``make touch`` build target
--------------------------------------
The ``make touch`` build target previously used to request implicit regeneration
of generated files by updating their modification times has been removed.
It has been replaced by the new ``make regen-all`` target.
(Contributed by Victor Stinner in :issue:`23404`.)
.. versionchanged:: 3.5.4