What’s New In Python 3.5

What’s New In Python 3.5¶
- Editors:
Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io>
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 for a full list of changes.
See also
PEP 478 - Python 3.5 Release Schedule
Summary – Release highlights¶
New syntax features:
PEP 492, coroutines with async and await syntax.
PEP 465, a new matrix multiplication operator:
a @ b
.PEP 448, additional unpacking generalizations.
New library modules:
New built-in features:
bytes % args
,bytearray % args
: PEP 461 – Adding%
formatting to bytes and bytearray.New
bytes.hex()
,bytearray.hex()
andmemoryview.hex()
methods. (Contributed by Arnon Yaari in bpo-9951.)memoryview
now supports tuple indexing (including multi-dimensional). (Contributed by Antoine Pitrou in bpo-23632.)Generators have a new
gi_yieldfrom
attribute, which returns the object being iterated byyield from
expressions. (Contributed by Benno Leslie and Yury Selivanov in bpo-24450.)A new
RecursionError
exception is now raised when maximum recursion depth is reached. (Contributed by Georg Brandl in bpo-19235.)
CPython implementation improvements:
When the
LC_TYPE
locale is the POSIX locale (C
locale),sys.stdin
andsys.stdout
now use thesurrogateescape
error handler, instead of thestrict
error handler. (Contributed by Victor Stinner in bpo-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files are no longer used and have been replaced by a more flexible scheme that includes the optimization level explicitly in.pyc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 PEP 488 overview.)Builtin and extension modules are now initialized in a multi-phase process, which is similar to how Python modules are loaded. (See PEP 489 overview.)
Significant improvements in the standard library:
collections.OrderedDict
is now implemented in C, which makes it 4 to 100 times faster.The
ssl
module gained support for Memory BIO, which decouples SSL protocol handling from network IO.The new
os.scandir()
function provides a better and significantly faster way of directory traversal.functools.lru_cache()
has been mostly reimplemented in C, yielding much better performance.The new
subprocess.run()
function provides a streamlined way to run subprocesses.The
traceback
module has been significantly enhanced for improved performance and developer convenience.
Security improvements:
SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a
ssl.SSLContext
manually. (See bpo-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 bpo-22796.)
Windows improvements:
A new installer for Windows has replaced the old MSI. See Using Python 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.
New Features¶
PEP 492 - Coroutines with async and await syntax¶
PEP 492 greatly improves support for asynchronous programming in Python by adding awaitable objects, coroutine functions, asynchronous iteration, and asynchronous context managers.
Coroutine functions are declared using the new async def
syntax:
>>> async def coro():
... return 'spam'
Inside a coroutine function, the new 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 awaitable protocol by
defining the __await__()
method.
PEP 492 also adds 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 async for
and async with
can only
be used inside a coroutine function declared with async def
.
Coroutine functions are intended to be run inside a compatible event loop, such as the asyncio loop.
Note
Changed in version 3.5.2: Starting with CPython 3.5.2, __aiter__
can directly return
asynchronous iterators. Returning
an awaitable object will result in a
PendingDeprecationWarning
.
See more details in the Asynchronous Iterators documentation section.
See also
- PEP 492 – Coroutines with async and await syntax
PEP written and implemented by Yury Selivanov.
PEP 465 - A dedicated infix operator for matrix multiplication¶
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 __matmul__()
,
__rmatmul__()
, and __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.])
See also
- PEP 465 – A dedicated infix operator for matrix multiplication
PEP written by Nathaniel J. Smith; implemented by Benjamin Peterson.
PEP 448 - Additional Unpacking Generalizations¶
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 function 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 Expression lists and Dictionary displays):
>>> *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}
See also
- PEP 448 – Additional Unpacking Generalizations
PEP written by Joshua Landau; implemented by Neil Girdhar, Thomas Wouters, and Joshua Landau.
PEP 461 - percent formatting support for bytes and bytearray¶
PEP 461 adds support for the %
interpolation operator to bytes
and 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.
See also
- PEP 461 – Adding % formatting to bytes and bytearray
PEP written by Ethan Furman; implemented by Neil Schemenauer and Ethan Furman.
PEP 484 - Type Hints¶
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 provisional module 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
__annotations__
attribute, no automatic type checking happens
at runtime. Instead, it is assumed that a separate off-line type checker
(e.g. mypy) will be used for on-demand
source code analysis.
The type system supports unions, generic types, and a special type
named Any
which is consistent with (i.e. assignable to
and from) all types.
PEP 471 - os.scandir() function – a better and faster directory iterator¶
PEP 471 adds a new directory iteration function, os.scandir()
,
to the standard library. Additionally, 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 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 os.scandir()
to display all
the files (excluding directories) in the given path that don’t start with
'.'
. The entry.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)
See also
- PEP 471 – os.scandir() function – a better and faster directory iterator
PEP written and implemented by Ben Hoyt with the help of Victor Stinner.
PEP 475: Retry system calls failing with EINTR¶
An 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 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 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:
functions of the
faulthandler
module;os
functions:fchdir()
,fchmod()
,fchown()
,fdatasync()
,fstat()
,fstatvfs()
,fsync()
,ftruncate()
,mkfifo()
,mknod()
,open()
,posix_fadvise()
,posix_fallocate()
,pread()
,pwrite()
,read()
,readv()
,sendfile()
,wait3()
,wait4()
,wait()
,waitid()
,waitpid()
,write()
,writev()
;special cases:
os.close()
andos.dup2()
now ignoreEINTR
errors; the syscall is not retried (see the PEP for the rationale);select
functions:devpoll.poll()
,epoll.poll()
,kqueue.control()
,poll.poll()
,select()
;methods of the
socket
class:accept()
,connect()
(except for non-blocking sockets),recv()
,recvfrom()
,recvmsg()
,send()
,sendall()
,sendmsg()
,sendto()
;
See also
- 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).
PEP 479: Change StopIteration handling inside generators¶
The interaction of generators and 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
RuntimeError
before it exits the generator frame. The main goal of
this change is to ease debugging in the situation where an unguarded
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 __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 PendingDeprecationWarning
will be
raised whenever a StopIteration
exception is raised inside a generator.
See also
- 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.
PEP 485: A function for testing approximate equality¶
PEP 485 adds the math.isclose()
and 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
See also
- PEP 485 – A function for testing approximate equality
PEP written by Christopher Barker; implemented by Chris Barker and Tal Einat.
PEP 486: Make the Python Launcher aware of virtual environments¶
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.
See also
- PEP 486 – Make the Python Launcher aware of virtual environments
PEP written and implemented by Paul Moore.
PEP 488: Elimination of PYO files¶
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
-O
or -OO
. Consequently, bytecode files generated from
-O
, and -OO
may now exist simultaneously.
importlib.util.cache_from_source()
has an updated API to help with
this change.
See also
- PEP 488 – Elimination of PYO files
PEP written and implemented by Brett Cannon.
PEP 489: Multi-phase extension module initialization¶
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.
See also
- PEP 489 – Multi-phase extension module initialization
PEP written by Petr Viktorin, Stefan Behnel, and Nick Coghlan; implemented by Petr Viktorin.
Other Language Changes¶
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 bpo-19676 and bpo-22286.)The
-b
option now affects comparisons ofbytes
withint
. (Contributed by Serhiy Storchaka in bpo-23681.)New Kazakh
kz1048
and Tajikkoi8_t
codecs. (Contributed by Serhiy Storchaka in bpo-22682 and bpo-22681.)Property docstrings are now writable. This is especially useful for
collections.namedtuple()
docstrings. (Contributed by Berker Peksag in bpo-24064.)Circular imports involving relative imports are now supported. (Contributed by Brett Cannon and Antoine Pitrou in bpo-17636.)
New Modules¶
typing¶
The new typing
provisional module
provides standard definitions and tools for function type annotations.
See Type Hints for more information.
zipapp¶
The new 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 bpo-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:
$ python -m zipapp myapp
$ python myapp.pyz
The module implementation has been contributed by Paul Moore in bpo-23491.
See also
PEP 441 – Improving Python ZIP Application Support
Improved Modules¶
argparse¶
The ArgumentParser
class now allows disabling
abbreviated usage of long options by setting
allow_abbrev to False
. (Contributed by Jonathan Paugh,
Steven Bethard, paul j3 and Daniel Eriksson in bpo-14910.)
asyncio¶
Since the asyncio
module is provisional,
all changes introduced in Python 3.5 have also been backported to Python 3.4.x.
Notable changes in the asyncio
module since Python 3.4.0:
New debugging APIs:
loop.set_debug()
andloop.get_debug()
methods. (Contributed by Victor Stinner.)The proactor event loop now supports SSL. (Contributed by Antoine Pitrou and Victor Stinner in bpo-22560.)
A new
loop.is_closed()
method to check if the event loop is closed. (Contributed by Victor Stinner in bpo-21326.)A new
loop.create_task()
to conveniently create and schedule a newTask
for a coroutine. Thecreate_task
method is also used by all asyncio functions that wrap coroutines into tasks, such asasyncio.wait()
,asyncio.gather()
, etc. (Contributed by Victor Stinner.)A new
transport.get_write_buffer_limits()
method to inquire for high- and low- water limits of the flow control. (Contributed by Victor Stinner.)The
async()
function is deprecated in favor ofensure_future()
. (Contributed by Yury Selivanov.)New
loop.set_task_factory()
andloop.get_task_factory()
methods to customize the task factory thatloop.create_task()
method uses. (Contributed by Yury Selivanov.)New
Queue.join()
andQueue.task_done()
queue methods. (Contributed by Victor Stinner.)The
JoinableQueue
class was removed, in favor of theasyncio.Queue
class. (Contributed by Victor Stinner.)
Updates in 3.5.1:
The
ensure_future()
function and all functions that use it, such asloop.run_until_complete()
, now accept all kinds of awaitable objects. (Contributed by Yury Selivanov.)New
run_coroutine_threadsafe()
function to submit coroutines to event loops from other threads. (Contributed by Vincent Michel.)New
Transport.is_closing()
method to check if the transport is closing or closed. (Contributed by Yury Selivanov.)The
loop.create_server()
method can now accept a list of hosts. (Contributed by Yann Sionneau.)
Updates in 3.5.2:
New
loop.create_future()
method to create Future objects. This allows alternative event loop implementations, such as uvloop, to provide a fasterasyncio.Future
implementation. (Contributed by Yury Selivanov.)New
loop.get_exception_handler()
method to get the current exception handler. (Contributed by Yury Selivanov.)New
StreamReader.readuntil()
method to read data from the stream until a separator bytes sequence appears. (Contributed by Mark Korenberg.)The
loop.create_connection()
andloop.create_server()
methods are optimized to avoid calling the systemgetaddrinfo
function if the address is already resolved. (Contributed by A. Jesse Jiryu Davis.)The
loop.sock_connect(sock, address)
no longer requires the address to be resolved prior to the call. (Contributed by A. Jesse Jiryu Davis.)
bz2¶
The BZ2Decompressor.decompress
method now accepts an optional max_length argument to limit the maximum
size of decompressed data. (Contributed by Nikolaus Rath in bpo-15955.)
cgi¶
The FieldStorage
class now supports the context manager
protocol. (Contributed by Berker Peksag in bpo-20289.)
cmath¶
A new function isclose()
provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in bpo-24270.)
code¶
The InteractiveInterpreter.showtraceback()
method now prints the full chained traceback, just like the interactive
interpreter. (Contributed by Claudiu Popa in bpo-17442.)
collections¶
The OrderedDict
class is now implemented in C, which
makes it 4 to 100 times faster. (Contributed by Eric Snow in bpo-16991.)
OrderedDict.items()
, OrderedDict.keys()
,
and OrderedDict.values()
views now support reversed()
iteration.
(Contributed by Serhiy Storchaka in bpo-19505.)
The deque
class now defines
index()
, insert()
, and
copy()
, and supports the +
and *
operators.
This allows deques to be recognized as a MutableSequence
and improves their substitutability for lists.
(Contributed by Raymond Hettinger in bpo-23704.)
Docstrings produced by namedtuple()
can now be updated:
Point = namedtuple('Point', ['x', 'y'])
Point.__doc__ += ': Cartesian coordinate'
Point.x.__doc__ = 'abscissa'
Point.y.__doc__ = 'ordinate'
(Contributed by Berker Peksag in bpo-24064.)
The UserString
class now implements the
__getnewargs__()
, __rmod__()
, casefold()
,
format_map()
, isprintable()
, and maketrans()
methods to match the corresponding methods of str
.
(Contributed by Joe Jevnik in bpo-22189.)
collections.abc¶
The Sequence.index()
method now
accepts start and stop arguments to match the corresponding methods
of tuple
, list
, etc.
(Contributed by Devin Jeanpierre in bpo-23086.)
A new Generator
abstract base class. (Contributed
by Stefan Behnel in bpo-24018.)
New Awaitable
, Coroutine
,
AsyncIterator
, and
AsyncIterable
abstract base classes.
(Contributed by Yury Selivanov in bpo-24184.)
For earlier Python versions, a backport of the new ABCs is available in an external PyPI package.
compileall¶
A new compileall
option, -j N
, allows running N workers
simultaneously to perform parallel bytecode compilation.
The compile_dir()
function has a corresponding workers
parameter. (Contributed by Claudiu Popa in bpo-16104.)
Another new option, -r
, allows controlling the maximum recursion
level for subdirectories. (Contributed by Claudiu Popa in bpo-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 compile_dir()
,
compile_file()
, and compile_path()
can now
accept an integer value indicating the level of output suppression.
(Contributed by Thomas Kluyver in bpo-21338.)
concurrent.futures¶
The Executor.map()
method now accepts a
chunksize argument to allow batching of tasks to improve performance when
ProcessPoolExecutor()
is used.
(Contributed by Dan O’Reilly in bpo-11271.)
The number of workers in the ThreadPoolExecutor
constructor is optional now. The default value is 5 times the number of CPUs.
(Contributed by Claudiu Popa in bpo-21527.)
configparser¶
configparser
now provides a way to customize the conversion
of values by specifying a dictionary of converters in the
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 bpo-18159.)
contextlib¶
The new redirect_stderr()
context manager (similar to
redirect_stdout()
) makes it easier for utility scripts to
handle inflexible APIs that write their output to 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 bpo-22389.)
csv¶
The writerow()
method now supports arbitrary iterables,
not just sequences. (Contributed by Serhiy Storchaka in bpo-23171.)
curses¶
The new update_lines_cols()
function updates the LINES
and COLS
module variables. This is useful for detecting
manual screen resizing. (Contributed by Arnon Yaari in bpo-4254.)
dbm¶
dumb.open
always creates a new database when the flag
has the value "n"
. (Contributed by Claudiu Popa in bpo-18039.)
difflib¶
The charset of HTML documents generated by
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 bpo-2052.)
The 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 bpo-17445.)
distutils¶
Both the build
and build_ext
commands now accept a -j
option to
enable parallel building of extension modules.
(Contributed by Antoine Pitrou in bpo-5309.)
The distutils
module now supports xz
compression, and can be
enabled by passing xztar
as an argument to bdist --format
.
(Contributed by Serhiy Storchaka in bpo-16314.)
doctest¶
The DocTestSuite()
function returns an empty
unittest.TestSuite
if module contains no docstrings, instead of
raising ValueError
. (Contributed by Glenn Jones in bpo-15916.)
email¶
A new policy option 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
compat32
and False
for all other policies.
(Contributed by Milan Oberkirch in bpo-20098.)
A new
Message.get_content_disposition()
method provides easy access to a canonical value for the
Content-Disposition header.
(Contributed by Abhilash Raj in bpo-21083.)
A new policy option 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
bpo-24211.)
The mime.text.MIMEText
constructor now
accepts a charset.Charset
instance.
(Contributed by Claude Paroz and Berker Peksag in bpo-16324.)
enum¶
The 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 bpo-21706.)
faulthandler¶
The enable()
, register()
,
dump_traceback()
and
dump_traceback_later()
functions now accept file
descriptors in addition to file-like objects.
(Contributed by Wei Wu in bpo-23566.)
functools¶
Most of the lru_cache()
machinery is now implemented in C, making
it significantly faster. (Contributed by Matt Joiner, Alexey Kachayev, and
Serhiy Storchaka in bpo-14373.)
glob¶
The iglob()
and glob()
functions now support recursive
search in subdirectories, using the "**"
pattern.
(Contributed by Serhiy Storchaka in bpo-13968.)
gzip¶
The mode argument of the GzipFile
constructor now
accepts "x"
to request exclusive creation.
(Contributed by Tim Heaney in bpo-19222.)
heapq¶
Element comparison in merge()
can now be customized by
passing a 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 bpo-13742.)
http¶
A new HTTPStatus
enum that defines a set of
HTTP status codes, reason phrases and long descriptions written in English.
(Contributed by Demian Brecht in bpo-21793.)
http.client¶
HTTPConnection.getresponse()
now raises a RemoteDisconnected
exception when a
remote server connection is closed unexpectedly. Additionally, if a
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 bpo-3566.)
idlelib and IDLE¶
Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release. See
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 dialog.
imaplib¶
The IMAP4
class now supports the context manager protocol.
When used in a with
statement, the IMAP4 LOGOUT
command will be called automatically at the end of the block.
(Contributed by Tarek Ziadé and Serhiy Storchaka in bpo-4972.)
The imaplib
module now supports RFC 5161 (ENABLE Extension)
and RFC 6855 (UTF-8 Support) via the IMAP4.enable()
method. A new IMAP4.utf8_enabled
attribute tracks whether or not RFC 6855 support is enabled.
(Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in
bpo-21800.)
The imaplib
module now automatically encodes non-ASCII string usernames
and passwords using UTF-8, as recommended by the RFCs. (Contributed by Milan
Oberkirch in bpo-21800.)
imghdr¶
The what()
function now recognizes the
OpenEXR format
(contributed by Martin Vignali and Claudiu Popa in bpo-20295),
and the WebP format
(contributed by Fabrice Aneche and Claudiu Popa in bpo-20197.)
importlib¶
The util.LazyLoader
class allows for
lazy loading of modules in applications where startup time is important.
(Contributed by Brett Cannon in bpo-17621.)
The 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 bpo-21156.)
The new util.module_from_spec()
function is now the preferred way to create a new module. As opposed to
creating a 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 bpo-20383.)
inspect¶
Both the Signature
and Parameter
classes are
now picklable and hashable. (Contributed by Yury Selivanov in bpo-20726
and bpo-20334.)
A new
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 bpo-24190.)
A new class method
Signature.from_callable()
makes
subclassing of Signature
easier. (Contributed
by Yury Selivanov and Eric Snow in bpo-17373.)
The 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 bpo-20691.)
A set of new functions to inspect
coroutine functions and
coroutine objects has been added:
iscoroutine()
, iscoroutinefunction()
,
isawaitable()
, getcoroutinelocals()
,
and getcoroutinestate()
.
(Contributed by Yury Selivanov in bpo-24017 and bpo-24400.)
The stack()
, trace()
,
getouterframes()
, and getinnerframes()
functions now return a list of named tuples.
(Contributed by Daniel Shahaf in bpo-16808.)
io¶
A new BufferedIOBase.readinto1()
method, that uses at most one call to the underlying raw stream’s
RawIOBase.read()
or
RawIOBase.readinto()
methods.
(Contributed by Nikolaus Rath in bpo-20578.)
ipaddress¶
Both the IPv4Network
and 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 bpo-16531.)
A new reverse_pointer
attribute for the
IPv4Address
and IPv6Address
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 bpo-20480.)
json¶
The 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 bpo-21650.)
JSON decoder now raises JSONDecodeError
instead of
ValueError
to provide better context information about the error.
(Contributed by Serhiy Storchaka in bpo-19361.)
linecache¶
A new lazycache()
function can be used to capture information
about a non-file-based module to permit getting its lines later via
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 bpo-17911.)
locale¶
A new 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 bpo-13918.)
logging¶
All logging methods (Logger
log()
,
exception()
, critical()
,
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 bpo-20537.)
The handlers.HTTPHandler
class now
accepts an optional ssl.SSLContext
instance to configure SSL
settings used in an HTTP connection.
(Contributed by Alex Gaynor in bpo-22788.)
The 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.)
lzma¶
The LZMADecompressor.decompress()
method now accepts an optional max_length argument to limit the maximum
size of decompressed data.
(Contributed by Martin Panter in bpo-15955.)
math¶
Two new constants have been added to the math
module: inf
and nan
. (Contributed by Mark Dickinson in bpo-23185.)
A new function isclose()
provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in bpo-24270.)
A new gcd()
function has been added. The fractions.gcd()
function is now deprecated. (Contributed by Mark Dickinson and Serhiy
Storchaka in bpo-22486.)
multiprocessing¶
sharedctypes.synchronized()
objects now support the context manager protocol.
(Contributed by Charles-François Natali in bpo-21565.)
operator¶
attrgetter()
, itemgetter()
,
and methodcaller()
objects now support pickling.
(Contributed by Josh Rosenberg and Serhiy Storchaka in bpo-22955.)
New matmul()
and imatmul()
functions
to perform matrix multiplication.
(Contributed by Benjamin Peterson in bpo-21176.)
os¶
The new scandir()
function returning an iterator of
DirEntry
objects has been added. If possible, 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 bpo-22524.)
On Windows, a new
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 bpo-21719.)
The 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 bpo-22181.)
New get_blocking()
and set_blocking()
functions allow
getting and setting a file descriptor’s blocking mode (O_NONBLOCK
.)
(Contributed by Victor Stinner in bpo-22054.)
The truncate()
and ftruncate()
functions are now supported
on Windows. (Contributed by Steve Dower in bpo-23668.)
There is a new os.path.commonpath()
function returning the longest
common sub-path of each passed pathname. Unlike the
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 bpo-10395.)
pathlib¶
The new Path.samefile()
method can be used
to check whether the path points to the same file as another path, which can
be either another 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 bpo-19775.)
The Path.mkdir()
method now accepts a new optional
exist_ok argument to match mkdir -p
and os.makedirs()
functionality. (Contributed by Berker Peksag in bpo-21539.)
There is a new Path.expanduser()
method to
expand ~
and ~user
prefixes. (Contributed by Serhiy Storchaka and
Claudiu Popa in bpo-19776.)
A new Path.home()
class method can be used to get
a Path
instance representing the user’s home
directory.
(Contributed by Victor Salgado and Mayank Tripathi in bpo-19777.)
New Path.write_text()
,
Path.read_text()
,
Path.write_bytes()
,
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 bpo-20218.)
pickle¶
Nested objects, such as unbound methods or nested classes, can now be pickled using pickle protocols older than protocol version 4. Protocol version 4 already supports these cases. (Contributed by Serhiy Storchaka in bpo-23611.)
poplib¶
A new POP3.utf8()
command enables RFC 6856
(Internationalized Email) support, if a POP server supports it.
(Contributed by Milan OberKirch in bpo-21804.)
re¶
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 bpo-9179.)
The number of capturing groups in regular expressions is no longer limited to 100. (Contributed by Serhiy Storchaka in bpo-22437.)
The sub()
and subn()
functions now replace unmatched
groups with empty strings instead of raising an exception.
(Contributed by Serhiy Storchaka in bpo-1519638.)
The re.error
exceptions have new attributes,
msg
, pattern
,
pos
, lineno
,
and 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 bpo-22578.)
readline¶
A new 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 bpo-22940.)
selectors¶
The new DevpollSelector
supports efficient
/dev/poll
polling on Solaris.
(Contributed by Giampaolo Rodola’ in bpo-18931.)
shutil¶
The move()
function now accepts a copy_function argument,
allowing, for example, the copy()
function to be used instead of
the default copy2()
if there is a need to ignore file metadata
when moving.
(Contributed by Claudiu Popa in bpo-19840.)
The make_archive()
function now supports the xztar format.
(Contributed by Serhiy Storchaka in bpo-5411.)
signal¶
On Windows, the set_wakeup_fd()
function now also supports
socket handles. (Contributed by Victor Stinner in bpo-22018.)
Various SIG*
constants in the signal
module have been converted into
Enums
. This allows meaningful names to be printed
during debugging, instead of integer “magic numbers”.
(Contributed by Giampaolo Rodola’ in bpo-21076.)
smtpd¶
Both the SMTPServer
and 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
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 bpo-19662.)
The 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
SMTPServer.process_message()
via the mail_options keyword.
(Contributed by Milan Oberkirch and R. David Murray in bpo-21795.)
The 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
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 bpo-21725.)
It is now possible to provide, directly or via name resolution, IPv6
addresses in the SMTPServer
constructor, and have it
successfully connect. (Contributed by Milan Oberkirch in bpo-14758.)
smtplib¶
A new SMTP.auth()
method provides a convenient way to
implement custom authentication mechanisms. (Contributed by Milan
Oberkirch in bpo-15014.)
The SMTP.set_debuglevel()
method now
accepts an additional debuglevel (2), which enables timestamps in debug
messages. (Contributed by Gavin Chappell and Maciej Szulik in bpo-16914.)
Both the SMTP.sendmail()
and
SMTP.send_message()
methods now
support RFC 6531 (SMTPUTF8).
(Contributed by Milan Oberkirch and R. David Murray in bpo-22027.)
sndhdr¶
The what()
and whathdr()
functions now return
a namedtuple()
. (Contributed by Claudiu Popa in
bpo-18615.)
socket¶
Functions with timeouts now use a monotonic clock, instead of a system clock. (Contributed by Victor Stinner in bpo-22043.)
A new socket.sendfile()
method allows
sending a file over a socket by using the high-performance os.sendfile()
function on UNIX, resulting in uploads being from 2 to 3 times faster than when
using plain socket.send()
.
(Contributed by Giampaolo Rodola’ in bpo-17552.)
The 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 bpo-23853.)
The backlog argument of the socket.listen()
method is now optional. By default it is set to
SOMAXCONN
or to 128
, whichever is less.
(Contributed by Charles-François Natali in bpo-21455.)
ssl¶
Memory BIO Support¶
(Contributed by Geert Jansen in bpo-21965.)
The new SSLObject
class has been added to provide SSL protocol
support for cases when the network I/O capabilities of 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 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 SSLSocket
’s readiness
model (“select/poll”) is inefficient.
A new SSLContext.wrap_bio()
method can be used
to create a new SSLObject
instance.
Application-Layer Protocol Negotiation Support¶
(Contributed by Benjamin Peterson in bpo-20188.)
Where OpenSSL support is present, the ssl
module now implements
the Application-Layer Protocol Negotiation TLS extension as described
in RFC 7301.
The new SSLContext.set_alpn_protocols()
can be used to specify which protocols a socket should advertise during
the TLS handshake.
The new
SSLSocket.selected_alpn_protocol()
returns the protocol that was selected during the TLS handshake.
The HAS_ALPN
flag indicates whether ALPN support is present.
Other Changes¶
There is a new SSLSocket.version()
method to
query the actual protocol version in use.
(Contributed by Antoine Pitrou in bpo-20421.)
The SSLSocket
class now implements
a SSLSocket.sendfile()
method.
(Contributed by Giampaolo Rodola’ in bpo-17552.)
The SSLSocket.send()
method now raises either
the ssl.SSLWantReadError
or ssl.SSLWantWriteError
exception on a
non-blocking socket if the operation would block. Previously, it would return
0
. (Contributed by Nikolaus Rath in bpo-20951.)
The 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 int
. (Contributed by Akira Li in bpo-19940.)
New SSLObject.shared_ciphers()
and
SSLSocket.shared_ciphers()
methods return
the list of ciphers sent by the client during the handshake.
(Contributed by Benjamin Peterson in bpo-23186.)
The SSLSocket.do_handshake()
,
SSLSocket.read()
,
SSLSocket.shutdown()
, and
SSLSocket.write()
methods of the 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 bpo-23853.)
The match_hostname()
function now supports matching of IP addresses.
(Contributed by Antoine Pitrou in bpo-23239.)
sqlite3¶
The Row
class now fully supports the sequence protocol,
in particular reversed()
iteration and slice indexing.
(Contributed by Claudiu Popa in bpo-10203; by Lucas Sinclair,
Jessica McKellar, and Serhiy Storchaka in bpo-13583.)
subprocess¶
The new run()
function has been added.
It runs the specified command and returns a
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 bpo-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 set_coroutine_wrapper()
function allows setting a global
hook that will be called whenever a coroutine object
is created by an async def
function. A corresponding
get_coroutine_wrapper()
can be used to obtain a currently set
wrapper. Both functions are provisional,
and are intended for debugging purposes only. (Contributed by Yury Selivanov
in bpo-24017.)
A new is_finalizing()
function can be used to check if the Python
interpreter is shutting down.
(Contributed by Antoine Pitrou in bpo-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 bpo-23437.)
tarfile¶
The mode argument of the open()
function now accepts "x"
to request exclusive creation. (Contributed by Berker Peksag in bpo-21717.)
The TarFile.extractall()
and
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 bpo-23193.)
The TarFile.list()
now accepts an optional
members keyword argument that can be set to a subset of the list returned
by TarFile.getmembers()
.
(Contributed by Serhiy Storchaka in bpo-21549.)
threading¶
Both the Lock.acquire()
and
RLock.acquire()
methods
now use a monotonic clock for timeout management.
(Contributed by Victor Stinner in bpo-22043.)
time¶
The monotonic()
function is now always available.
(Contributed by Victor Stinner in bpo-22043.)
timeit¶
A new command line option -u
or --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 bpo-18983.)
The timeit()
function has a new globals parameter for
specifying the namespace in which the code will be running.
(Contributed by Ben Roberts in bpo-2527.)
tkinter¶
The tkinter._fix
module used for setting up the Tcl/Tk environment
on Windows has been replaced by a private function in the _tkinter
module which makes no permanent changes to environment variables.
(Contributed by Zachary Ware in bpo-20035.)
traceback¶
New walk_stack()
and walk_tb()
functions to conveniently traverse frame and
traceback objects.
(Contributed by Robert Collins in bpo-17911.)
New lightweight classes: TracebackException
,
StackSummary
, and FrameSummary
.
(Contributed by Robert Collins in bpo-17911.)
Both the print_tb()
and print_stack()
functions
now support negative values for the limit argument.
(Contributed by Dmitry Kazakov in bpo-22619.)
types¶
A new coroutine()
function to transform
generator and
generator-like
objects into
awaitables.
(Contributed by Yury Selivanov in bpo-24017.)
A new type called CoroutineType
, which is used for
coroutine objects created by async def
functions.
(Contributed by Yury Selivanov in bpo-24400.)
unicodedata¶
The unicodedata
module now uses data from Unicode 8.0.0.
unittest¶
The 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 bpo-16662.)
Unittest discovery errors now are exposed in the
TestLoader.errors
attribute of the
TestLoader
instance.
(Contributed by Robert Collins in bpo-19746.)
A new command line option --locals
to show local variables in
tracebacks. (Contributed by Robert Collins in bpo-22936.)
unittest.mock¶
The Mock
class has the following improvements:
The class constructor has a new unsafe parameter, which causes mock objects to raise
AttributeError
on attribute names starting with"assert"
. (Contributed by Kushal Das in bpo-21238.)A new
Mock.assert_not_called()
method to check if the mock object was called. (Contributed by Kushal Das in bpo-21262.)
The MagicMock
class now supports
__truediv__()
, __divmod__()
and __matmul__()
operators.
(Contributed by Johannes Baiter in bpo-20968, and Håkan Lövdahl
in bpo-23581 and bpo-23568.)
It is no longer necessary to explicitly pass create=True
to the
patch()
function when patching builtin names.
(Contributed by Kushal Das in bpo-17660.)
urllib¶
A new
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 bpo-19494 and Akshit Khurana in
bpo-7159.)
A new quote_via argument for the
parse.urlencode()
function provides a way to control the encoding of query parts if needed.
(Contributed by Samwyse and Arnon Yaari in bpo-13866.)
The request.urlopen()
function accepts an
ssl.SSLContext
object as a context argument, which will be used for
the HTTPS connection. (Contributed by Alex Gaynor in bpo-22366.)
The 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 bpo-22118.)
wsgiref¶
The headers argument of the headers.Headers
class constructor is now optional.
(Contributed by Pablo Torres Navarrete and SilentGhost in bpo-5800.)
xmlrpc¶
The client.ServerProxy
class now supports
the context manager protocol.
(Contributed by Claudiu Popa in bpo-20627.)
The client.ServerProxy
constructor now accepts
an optional ssl.SSLContext
instance.
(Contributed by Alex Gaynor in bpo-22960.)
xml.sax¶
SAX parsers now support a character stream of the
xmlreader.InputSource
object.
(Contributed by Serhiy Storchaka in bpo-2175.)
parseString()
now accepts a str
instance.
(Contributed by Serhiy Storchaka in bpo-10590.)
zipfile¶
ZIP output can now be written to unseekable streams. (Contributed by Serhiy Storchaka in bpo-23252.)
The mode argument of ZipFile.open()
method now
accepts "x"
to request exclusive creation.
(Contributed by Serhiy Storchaka in bpo-21717.)
Other module-level changes¶
Many functions in the mmap
, ossaudiodev
, socket
,
ssl
, and codecs
modules now accept writable
bytes-like objects.
(Contributed by Serhiy Storchaka in bpo-23001.)
Optimizations¶
The 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 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 bpo-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 bpo-21233.)
Some operations on ipaddress
IPv4Network
and
IPv6Network
have been massively sped up, such as
subnets()
, supernet()
,
summarize_address_range()
, collapse_addresses()
.
The speed up can range from 3 to 15 times.
(Contributed by Antoine Pitrou, Michel Albert, and Markus in
bpo-21486, bpo-21487, bpo-20826, bpo-23266.)
Pickling of ipaddress
objects was optimized to produce significantly
smaller output. (Contributed by Serhiy Storchaka in bpo-23133.)
Many operations on io.BytesIO
are now 50% to 100% faster.
(Contributed by Serhiy Storchaka in bpo-15381 and David Wilson in
bpo-22003.)
The 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 bpo-20416 and bpo-23344.)
The UTF-32 encoder is now 3 to 7 times faster. (Contributed by Serhiy Storchaka in bpo-15027.)
Regular expressions are now parsed up to 10% faster. (Contributed by Serhiy Storchaka in bpo-19380.)
The json.dumps()
function was optimized to run with
ensure_ascii=False
as fast as with ensure_ascii=True
.
(Contributed by Naoki Inada in bpo-23206.)
The PyObject_IsInstance()
and PyObject_IsSubclass()
functions have been sped up in the common case that the second argument
has type
as its metaclass.
(Contributed Georg Brandl by in bpo-22540.)
Method caching was slightly improved, yielding up to 5% performance improvement in some benchmarks. (Contributed by Antoine Pitrou in bpo-22847.)
Objects from the random
module now use 50% less memory on 64-bit
builds. (Contributed by Serhiy Storchaka in bpo-23488.)
The property()
getter calls are up to 25% faster.
(Contributed by Joe Jevnik in bpo-23910.)
Instantiation of fractions.Fraction
is now up to 30% faster.
(Contributed by Stefan Behnel in bpo-22464.)
String methods find()
, rfind()
, split()
,
partition()
and the in
string operator are now significantly
faster for searching 1-character substrings.
(Contributed by Serhiy Storchaka in bpo-23573.)
Build and C API Changes¶
New calloc
functions were added:
(Contributed by Victor Stinner in bpo-21233.)
New encoding/decoding helper functions:
Py_DecodeLocale()
(replaced_Py_char2wchar()
),Py_EncodeLocale()
(replaced_Py_wchar2char()
).
(Contributed by Victor Stinner in bpo-18395.)
A new PyCodec_NameReplaceErrors()
function to replace the unicode
encode error with \N{...}
escapes.
(Contributed by Serhiy Storchaka in bpo-19676.)
A new PyErr_FormatV()
function similar to PyErr_Format()
,
but accepts a va_list
argument.
(Contributed by Antoine Pitrou in bpo-18711.)
A new PyExc_RecursionError
exception.
(Contributed by Georg Brandl in bpo-19235.)
New PyModule_FromDefAndSpec()
, PyModule_FromDefAndSpec2()
,
and PyModule_ExecDef()
functions introduced by PEP 489 –
multi-phase extension module initialization.
(Contributed by Petr Viktorin in bpo-24268.)
New PyNumber_MatrixMultiply()
and
PyNumber_InPlaceMatrixMultiply()
functions to perform matrix
multiplication.
(Contributed by Benjamin Peterson in bpo-21176. See also PEP 465
for details.)
The 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.
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 is3
.<minor>
is the minor number of the Python version; for Python 3.5 this is5
.<architecture>
is the hardware architecture the extension module was built to run on. It’s most commonly eitheri386
for 32-bit Intel platforms orx86_64
for 64-bit Intel (and AMD) platforms.<os>
is alwayslinux-gnu
, except for extensions built to talk to the 32-bit ABI on 64-bit platforms, in which case it islinux-gnu32
(and<architecture>
will bex86_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 is3
.<minor>
is the minor number of the Python version; for Python 3.5 this is5
.<platform>
is the platform the extension module was built for, eitherwin32
for Win32,win_amd64
for Win64,win_ia64
for Windows Itanium 64, andwin_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 StopIteration
exception inside a generator will now generate a silent
PendingDeprecationWarning
, which will become a non-silent deprecation
warning in Python 3.6 and will trigger a RuntimeError
in Python 3.7.
See PEP 479: Change StopIteration handling inside generators
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 formatter
module has now graduated to full deprecation and is still
slated for removal in Python 3.6.
The asyncio.async()
function is deprecated in favor of
ensure_future()
.
The 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 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 key
,
value
and
coded_value
of http.cookies.Morsel
objects is deprecated. Use the set()
method
instead. In addition, the undocumented LegalChars parameter of
set()
is deprecated, and is now ignored.
Passing a format string as keyword argument format_string to the
format()
method of the string.Formatter
class has been deprecated.
(Contributed by Serhiy Storchaka in bpo-23671.)
The platform.dist()
and 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 bpo-1322.)
The previously undocumented from_function
and from_builtin
methods of
inspect.Signature
are deprecated. Use the new
Signature.from_callable()
method instead. (Contributed by Yury Selivanov in bpo-24248.)
The inspect.getargspec()
function is deprecated and scheduled to be
removed in Python 3.6. (See bpo-20438 for details.)
The inspect
getfullargspec()
,
getcallargs()
, and formatargspec()
functions are
deprecated in favor of the inspect.signature()
API. (Contributed by Yury
Selivanov in bpo-20438.)
getargvalues()
and formatargvalues()
functions
were inadvertently marked as deprecated with the release of Python 3.5.0.
Use of re.LOCALE
flag with str patterns or re.ASCII
is now
deprecated. (Contributed by Serhiy Storchaka in bpo-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 bpo-23622.)
The undocumented and unofficial use_load_tests default argument of the
unittest.TestLoader.loadTestsFromModule()
method now is
deprecated and ignored.
(Contributed by Robert Collins and Barry A. Warsaw in bpo-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 theftplib
module was deprecated in 3.4, and has now been removed. (Contributed by Matt Chaput in bpo-6623.)The concept of
.pyo
files has been removed.The JoinableQueue class in the provisional
asyncio
module was deprecated in 3.4.4 and is now removed. (Contributed by A. Jesse Jiryu Davis in bpo-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
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
InterruptedError
if the Python signal handler does not raise an exception.Before Python 3.5, a
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 bpo-13936 for full details.The
ssl.SSLSocket.send()
method now raises eitherssl.SSLWantReadError
orssl.SSLWantWriteError
on a non-blocking socket if the operation would block. Previously, it would return0
. (Contributed by Nikolaus Rath in bpo-20951.)The
__name__
attribute of generators is now set from the function name, instead of being set from the code name. Usegen.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 bpo-21205.)The deprecated “strict” mode and argument of
HTMLParser
,HTMLParser.error()
, and theHTMLParserError
exception have been removed. (Contributed by Ezio Melotti in bpo-15114.) The convert_charrefs argument ofHTMLParser
is nowTrue
by default. (Contributed by Berker Peksag in bpo-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 bytes-like object is required, not ‘sometype’”. (Contributed by Ezio Melotti in bpo-16518.)
If the current directory is set to a directory that no longer exists then
FileNotFoundError
will no longer be raised and insteadfind_spec()
will returnNone
without cachingNone
insys.path_importer_cache
, which is different than the typical case (bpo-22834).HTTP status code and messages from
http.client
andhttp.server
were refactored into a commonHTTPStatus
enum. The values inhttp.client
andhttp.server
remain available for backwards compatibility. (Contributed by Demian Brecht in bpo-21793.)When an import loader defines
exec_module()
it is now expected to also definecreate_module()
(raises aDeprecationWarning
now, will be an error in Python 3.6). If the loader inherits fromimportlib.abc.Loader
then there is nothing to do, else simply definecreate_module()
to returnNone
. (Contributed by Brett Cannon in bpo-23014.)The
re.split()
function always ignored empty pattern matches, so the"x*"
pattern worked the same as"x+"
, and the"\b"
pattern never worked. Nowre.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 bpo-22818.)The
http.cookies.Morsel
dict-like interface has been made self consistent: morsel comparison now takes thekey
andvalue
into account,copy()
now results in aMorsel
instance rather than adict
, andupdate()
will now raise an exception if any of the keys in the update dictionary are invalid. In addition, the undocumented LegalChars parameter ofset()
is deprecated and is now ignored. (Contributed by Demian Brecht in bpo-2211.)PEP 488 has removed
.pyo
files from Python and introduced the optionalopt-
tag in.pyc
file names. Theimportlib.util.cache_from_source()
has gained an optimization parameter to help control theopt-
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
socket
module now exports theCAN_RAW_FD_FRAMES
constant on linux 3.6 and greater.The
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 anint
. (Contributed by Akira Li in bpo-19940.)The
pygettext.py
Tool now uses the standard +NNNN format for timezones in the POT-Creation-Date header.The
smtplib
module now usessys.stderr
instead of the previous module-levelstderr
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
str.startswith()
andstr.endswith()
methods no longer returnTrue
when finding the empty string and the indexes are completely out of range. (Contributed by Serhiy Storchaka in bpo-24284.)The
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 thepydoc
module and thehelp()
function. (Contributed by Serhiy Storchaka in bpo-15582.)Nested
functools.partial()
calls are now flattened. If you were relying on the previous behavior, you can now either add an attribute to afunctools.partial()
object or you can create a subclass offunctools.partial()
. (Contributed by Alexander Belopolsky in bpo-7830.)
Changes in the C API¶
The undocumented
format
member of the (non-public)PyMemoryViewObject
structure has been removed. All extensions relying on the relevant parts inmemoryobject.h
must be rebuilt.The
PyMemAllocator
structure was renamed toPyMemAllocatorEx
and a newcalloc
field was added.Removed non-documented macro
PyObject_REPR()
which leaked references. Use format character%R
inPyUnicode_FromFormat()
-like functions to format therepr()
of the object. (Contributed by Serhiy Storchaka in bpo-22453.)Because the lack of the
__module__
attribute breaks pickling and introspection, a deprecation warning is now raised for builtin types without the__module__
attribute. This will be anAttributeError
in the future. (Contributed by Serhiy Storchaka in bpo-20204.)As part of the PEP 492 implementation, the
tp_reserved
slot ofPyTypeObject
was replaced with atp_as_async
slot. Refer to Coroutine 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 Makefile.pre.in for details.
(Contributed by Victor Stinner in bpo-23404.)
Added in version 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 bpo-23404.)
Changed in version 3.5.4.

File
, line
, in
:
File
, line
, in
File
, line
, in
:
:
: