Python 3.5 有什么新变化

    Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <>

    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.

    参见

    - Python 3.5 发布计划

    新的语法特性：

    • PEP 492, 使用 async 和 await 语法实现协程。

    • , 新的矩阵乘法运算符: a @ b.

    • PEP 448, additional unpacking generalizations.

    新的库模块：

    新的内置特性：

    • bytes % args, bytearray % args: – Adding % formatting to bytes and bytearray.

    • New bytes.hex(), and memoryview.hex() methods. (Contributed by Arnon Yaari in .)

    • memoryview now supports tuple indexing (including multi-dimensional). (Contributed by Antoine Pitrou in .)

    • 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 bpo-24450.)

    • A new exception is now raised when maximum recursion depth is reached. (Contributed by Georg Brandl in bpo-19235.)

    CPython 实现的改进：

    • When the LC_TYPE locale is the POSIX locale (C locale), and sys.stdout now use the surrogateescape error handler, instead of the strict error handler. (Contributed by Victor Stinner in .)

    • .pyo files are no longer used and have been replaced by a more flexible scheme that includes the optimization level explicitly in .pyc name.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 .)

    标准库中的重大改进：

    • collections.OrderedDict is now , which makes it 4 to 100 times faster.

    • The ssl module gained , which decouples SSL protocol handling from network IO.

    • The new os.scandir() function provides a of directory traversal.

    • functools.lru_cache() has been mostly , yielding much better performance.

    • The new subprocess.run() function provides a .

    • The traceback module has been significantly for improved performance and developer convenience.

    安全改进：

    • SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a ssl.SSLContext manually. (See 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改进：

    • A new installer for Windows has replaced the old MSI. See 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.

    新的特性

    greatly improves support for asynchronous programming in Python by adding awaitable objects, , asynchronous iteration, and .

    Coroutine functions are declared using the new async def syntax:

    Inside a coroutine function, the new 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 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:

    1. import asyncio
    3. async def http_get(domain):
    4.     reader, writer = await asyncio.open_connection(domain, 80)
    6.     writer.write(b'\r\n'.join([
    7.         b'GET / HTTP/1.1',
    8.         b'Host: %b' % domain.encode('latin-1'),
    9.         b'Connection: close',
    10.         b'', b''
    11.     ]))
    13.     async for line in reader:
    14.         print('>>>', line)
    16.     writer.close()
    17. loop = asyncio.get_event_loop()
    18. try:
    19.     loop.run_until_complete(http_get('example.com'))
    20. finally:
    21.     loop.close()

    Similarly to asynchronous iteration, there is a new syntax for asynchronous context managers. The following script:

    1. import asyncio
    3. async def coro(name, lock):
    4.     print('coro {}: waiting for lock'.format(name))
    5.     async with lock:
    6.         print('coro {}: holding the lock'.format(name))
    7.         await asyncio.sleep(1)
    8.         print('coro {}: releasing the lock'.format(name))
    10. loop = asyncio.get_event_loop()
    11. lock = asyncio.Lock()
    12. coros = asyncio.gather(coro(1, lock), coro(2, lock))
    13. try:
    14.     loop.run_until_complete(coros)
    15. finally:
    16.     loop.close()

    将输出：

    1. coro 2: waiting for lock
    2. coro 2: holding the lock
    3. coro 1: waiting for lock
    4. coro 2: releasing the lock
    5. coro 1: holding the lock
    6. coro 1: releasing the lock

    Note that both and async with can only be used inside a coroutine function declared with .

    Coroutine functions are intended to be run inside a compatible event loop, such as the asyncio loop.

    注解

    在 3.5.2 版更改: Starting with CPython 3.5.2, __aiter__ can directly return . Returning an awaitable object will result in a .

    See more details in the 异步迭代器 documentation section.

    参见

    – 使用 async 和 await 语法实现协程

    PEP 由 Yury Selivanov 撰写并实现

    PEP 465 - 用于矩阵乘法的专用中缀运算符

    adds the @ infix operator for matrix multiplication. Currently, no builtin Python types implement the new operator, however, it can be implemented by defining __matmul__(), , 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.

    矩阵乘法在数学，科学，工程学的许多领域中是一种常见的操作，使用 @ 运算符可以编写更简洁的代码：

    1. S = (H @ beta - r).T @ inv(H @ V @ H.T) @ (H @ beta - r)

    代替：

    1. S = dot((dot(H, beta) - r).T,
    2.         dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))

    NumPy 1.10 支持新的运算符：

    1. >>> import numpy
    3. >>> x = numpy.ones(3)
    4. >>> x
    5. array([ 1., 1., 1.])
    7. >>> m = numpy.eye(3)
    8. >>> m
    9. array([[ 1., 0., 0.],
    10.        [ 0., 1., 0.],
    11.        [ 0., 0., 1.]])
    13. >>> x @ m
    14. array([ 1., 1., 1.])

    参见

    – 用于矩阵乘法的专用中缀运算符

    PEP 由 Nathaniel J. Smith 撰写，由 Benjamin Peterson 实现。

    PEP 448 - Additional Unpacking Generalizations

    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:

    1. >>> print(*[1], *[2], 3, *[4, 5])
    2. 1 2 3 4 5
    4. >>> def fn(a, b, c, d):
    5. ...     print(a, b, c, d)
    6. ...
    8. >>> fn(**{'a': 1, 'c': 3}, **{'b': 2, 'd': 4})
    9. 1 2 3 4

    Similarly, tuple, list, set, and dictionary displays allow multiple unpackings (see and 字典显示):

    1. >>> *range(4), 4
    2. (0, 1, 2, 3, 4)
    4. >>> [*range(4), 4]
    5. [0, 1, 2, 3, 4]
    7. >>> {*range(4), 4, *(5, 6, 7)}
    8. {0, 1, 2, 3, 4, 5, 6, 7}
    10. >>> {'x': 1, **{'y': 2}}
    11. {'x': 1, 'y': 2}

    参见

    – Additional Unpacking Generalizations

    PEP 由 Joshua Landau 撰写 ，由 Neil Girdhar，Thomas Wouters 和 Joshua Landau 实现。

    PEP 461 - percent formatting support for bytes and bytearray

    adds support for the % interpolation operator to 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.

    示例:

    1. >>> b'Hello %b!' % b'World'
    2. b'Hello World!'
    4. >>> b'x=%i y=%f' % (1, 2.5)
    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')):

    1. >>> b'Hello %b!' % 'World'
    2. Traceback (most recent call last):
    3.   File "<stdin>", line 1, in <module>
    4. TypeError: %b requires bytes, or an object that implements __bytes__, not 'str'
    6. >>> b'price: %a' % '10€'
    7. 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.

    参见

    – Adding % formatting to bytes and bytearray

    PEP 由 Ethan Furman 撰写 ，由 Neil Schemenauer 和 Ethan Furman 实现。

    PEP 484 - 类型提示

    Function annotation syntax has been a Python feature since version 3.0 (), 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 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:

    1. def greeting(name: str) -> str:
    2.     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 which is consistent with (i.e. assignable to and from) all types.

    参见

    • typing 模块文档

    • – 类型提示

      PEP 由 Guido van Rossum，Jukka Lehtosalo 和 Łukasz Langa 撰写，由 Guido van Rossum 实现。

    • PEP 483 – 类型提示理论

      PEP 由 Yury Selivanov 撰写

    PEP 471 - os.scandir() function – a better and faster directory iterator

    PEP 471 adds a new directory iteration function, , 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 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 call will generally not make an additional system call:

    参见

    PEP 471 – os.scandir() function – a better and faster directory iterator

    PEP 由 Ben Hoyt 在 Victor Stinner 的帮助下撰写并实现

    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 in such cases. This meant that, when writing a Python application, the developer had two choices:

    1. Ignore the InterruptedError.

    2. 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:

    1. print("Hello World")

    和:

    1. while True:
    2.     try:
    3.         print("Hello World")
    4.         break
    5.     except InterruptedError:
    6.         continue

    PEP 475 implements automatic retry of system calls on EINTR. This removes the burden of dealing with EINTR or 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:

    参见

    – 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 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 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 import is necessary:

    1. >>> from __future__ import generator_stop
    3. >>> def gen():
    4. ...     next(iter([]))
    5. ...     yield
    6. ...
    7. >>> next(gen())
    8. Traceback (most recent call last):
    9.   File "<stdin>", line 2, in gen
    10. StopIteration
    12. The above exception was the direct cause of the following exception:
    14. Traceback (most recent call last):
    15.   File "<stdin>", line 1, in <module>
    16. RuntimeError: generator raised StopIteration

    Without a __future__ import, a PendingDeprecationWarning will be raised whenever a StopIteration exception is raised inside a generator.

    参见

    – Change StopIteration handling inside generators

    PEP 由 Chris Angelico 和 Guido van Rossum 撰写，由 Chris Angelico，Yury Selivanov 和 Nick Coghlan 实现。

    PEP 485: A function for testing approximate equality

    adds the math.isclose() and 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:

    1. >>> import math
    2. >>> a = 5.0
    3. >>> b = 4.99998
    4. >>> math.isclose(a, b, rel_tol=1e-5)
    5. True
    6. >>> math.isclose(a, b, rel_tol=1e-6)
    7. False

    It is also possible to compare two values using absolute tolerance, which must be a non-negative value:

    1. >>> import math
    3. >>> b = 4.99998
    4. >>> math.isclose(a, b, abs_tol=0.00003)
    5. True
    6. >>> math.isclose(a, b, abs_tol=0.00001)
    7. False

    参见

    PEP 485 —— 用于测试近似相等的函数

    PEP 由 Christopher Barker 撰写，由 Chris Barker 和 Tal Einat 实现。

    PEP 486: Make the Python Launcher aware of virtual environments

    PEP 486 makes the Windows launcher (see ) 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.

    参见

    PEP 486 – Make the Python Launcher aware of virtual environments

    PEP 由 Paul Moore 撰写并实现

    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 or -OO. Consequently, bytecode files generated from , and -OO may now exist simultaneously. has an updated API to help with this change.

    参见

    PEP 488 – Elimination of PYO files

    PEP 由 Brett Cannon 撰写并实现。

    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 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.

    参见

    PEP 489 – Multi-phase extension module initialization

    PEP 由 Petr Viktorin , Stefan Behnel 和 Nick Coghlan 撰写，由 Petr Viktorin 实现。

    其他语言特性修改

    对Python 语言核心进行的小改动：

    • Added the "namereplace" error handlers. The "backslashreplace" error handlers now work with decoding and translating. (Contributed by Serhiy Storchaka in bpo-19676 and .)

    • The -b option now affects comparisons of with int. (Contributed by Serhiy Storchaka in .)

    • New Kazakh kz1048 and Tajik koi8_t codecs. (Contributed by Serhiy Storchaka in and bpo-22681.)

    • Property docstrings are now writable. This is especially useful for docstrings. (Contributed by Berker Peksag in bpo-24064.)

    • Circular imports involving relative imports are now supported. (Contributed by Brett Cannon and Antoine Pitrou in .)

    新增模块

    typing

    The new typing module provides standard definitions and tools for function type annotations. See Type Hints for more information.

    zipapp

    The new zipapp module (specified in ) 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:

    1. $ python -m zipapp myapp
    2. $ python myapp.pyz

    The module implementation has been contributed by Paul Moore in .

    参见

    PEP 441 – Improving Python ZIP Application Support

    argparse

    The ArgumentParser class now allows disabling of long options by setting allow_abbrev to False. (Contributed by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson in .)

    asyncio

    Since the module is provisional, all changes introduced in Python 3.5 have also been backported to Python 3.4.x.

    Notable changes in the module since Python 3.4.0:

    • New debugging APIs: loop.set_debug() and loop.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.create_task() to conveniently create and schedule a new for a coroutine. The create_task method is also used by all asyncio functions that wrap coroutines into tasks, such as asyncio.wait(), , 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 function is deprecated in favor of ensure_future(). (Contributed by Yury Selivanov.)

    • New and loop.get_task_factory() methods to customize the task factory that loop.create_task() method uses. (Contributed by Yury Selivanov.)

    • New and Queue.task_done() queue methods. (Contributed by Victor Stinner.)

    • The JoinableQueue class was removed, in favor of the class. (Contributed by Victor Stinner.)

    3.5.1 中的更新：

    • The ensure_future() function and all functions that use it, such as loop.run_until_complete(), now accept all kinds of . (Contributed by Yury Selivanov.)

    • New run_coroutine_threadsafe() function to submit coroutines to event loops from other threads. (Contributed by Vincent Michel.)

    • New 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.)

    3.5.2 中的更新：

    • New loop.create_future() method to create Future objects. This allows alternative event loop implementations, such as uvloop, to provide a faster 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() and 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 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 .)

    cgi

    The FieldStorage class now supports the 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 .)

    code

    The 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 .)

    OrderedDict.items(), OrderedDict.keys(), OrderedDict.values() views now support reversed() iteration. (Contributed by Serhiy Storchaka in .)

    The deque class now defines , insert(), and , 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 .)

    Docstrings produced by namedtuple() can now be updated:

    1. Point.__doc__ += ': Cartesian coodinate'
    2. Point.x.__doc__ = 'abscissa'
    3. Point.y.__doc__ = 'ordinate'

    （由 Berker Peksag 在 中贡献。）

    The UserString class now implements the , __rmod__(), , format_map(), , and maketrans() methods to match the corresponding methods of . (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, , etc. (Contributed by Devin Jeanpierre in bpo-23086.)

    A new abstract base class. (Contributed by Stefan Behnel in bpo-24018.)

    New , Coroutine, , and AsyncIterable abstract base classes. (Contributed by Yury Selivanov in .)

    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 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 .)

    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(), , and compile_path() can now accept an integer value indicating the level of output suppression. (Contributed by Thomas Kluyver in .)

    concurrent.futures

    The method now accepts a chunksize argument to allow batching of tasks to improve performance when ProcessPoolExecutor() is used. (Contributed by Dan O’Reilly in .)

    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 .)

    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.

    示例:

    1. >>> import configparser
    2. >>> conv = {}
    3. >>> conv['list'] = lambda v: [e.strip() for e in v.split() if e.strip()]
    4. >>> cfg = configparser.ConfigParser(converters=conv)
    5. >>> cfg.read_string("""
    6. ... [s]
    7. ... list = a b c d e f g
    8. ... """)
    9. >>> cfg.get('s', 'list')
    10. 'a b c d e f g'
    11. >>> cfg.getlist('s', 'list')
    12. ['a', 'b', 'c', 'd', 'e', 'f', 'g']
    13. >>> section = cfg['s']
    14. >>> section.getlist('list')
    15. ['a', 'b', 'c', 'd', 'e', 'f', 'g']

    （由 Łukasz Langa 在 中贡献。）

    contextlib

    The new context manager (similar to ) 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:

    1. >>> import contextlib, io, logging
    2. >>> f = io.StringIO()
    3. >>> with contextlib.redirect_stderr(f):
    4. ...     logging.warning('warning')
    5. ...
    6. >>> f.getvalue()
    7. 'WARNING:root:warning\n'

    （由 Berker Peksag 在 中贡献。）

    csv

    The 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 environment variables. This is useful for detecting manual screen resizing. (Contributed by Arnon Yaari in .)

    dbm

    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 .)

    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 .)

    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 .)

    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 .)

    doctest

    The function returns an empty unittest.TestSuite if module contains no docstrings, instead of raising . (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 and False for all other policies. (Contributed by Milan Oberkirch in bpo-20098.)

    A new method provides easy access to a canonical value for the Content-Disposition header. (Contributed by Abhilash Raj in bpo-21083.)

    A new policy option 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 SMTPUTF8 extension. (Contributed by R. David Murray in bpo-24211.)

    The constructor now accepts a charset.Charset instance. (Contributed by Claude Paroz and Berker Peksag in .)

    The Enum callable has a new parameter start to specify the initial number of enum values if only names are provided:

    1. >>> Animal = enum.Enum('Animal', 'cat dog', start=10)
    2. >>> Animal.cat
    3. <Animal.cat: 10>
    4. >>> Animal.dog
    5. <Animal.dog: 11>

    （由 Ethan Furman 在 中贡献。）

    faulthandler

    The , register(), and dump_traceback_later() functions now accept file descriptors in addition to file-like objects. (Contributed by Wei Wu in .)

    functools

    Most of the 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 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 .)

    heapq

    Element comparison in 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:

    1. >>> import heapq
    2. >>> a = ['9', '777', '55555']
    3. >>> b = ['88', '6666']
    4. >>> list(heapq.merge(a, b, key=len))
    5. ['9', '88', '777', '6666', '55555']
    6. >>> list(heapq.merge(reversed(a), reversed(b), key=len, reverse=True))
    7. ['55555', '6666', '777', '88', '9']

    （由 Raymond Hettinger 在 中贡献。）

    http

    A new 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 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:

    （由 Martin Panter 在 中贡献。）

    idlelib 与 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 Help ‣ About IDLE dialog.

    imaplib

    The IMAP4 class now supports the 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 .)

    The imaplib module now supports (ENABLE Extension) and RFC 6855 (UTF-8 Support) via the method. A new IMAP4.utf8_enabled attribute tracks whether or not support is enabled. (Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in bpo-21800.)

    The 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 format (contributed by Martin Vignali and Claudiu Popa in bpo-20295), and the 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 .)

    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 .)

    The new util.module_from_spec() function is now the preferred way to create a new module. As opposed to creating a 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 classes are now picklable and hashable. (Contributed by Yury Selivanov in bpo-20726 and .)

    A new BoundArguments.apply_defaults() method provides a way to set default values for missing arguments:

    1. >>> def foo(a, b='ham', *args): pass
    2. >>> ba = inspect.signature(foo).bind('spam')
    3. >>> ba.apply_defaults()
    4. >>> ba.arguments
    5. OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])

    （由 Yury Selivanov 在 中贡献。）

    A new class method Signature.from_callable() makes subclassing of easier. (Contributed by Yury Selivanov and Eric Snow in bpo-17373.)

    The 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 and coroutine objects has been added: , iscoroutinefunction(), , getcoroutinelocals(), and . (Contributed by Yury Selivanov in bpo-24017 and .)

    The stack(), , getouterframes(), and 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 or RawIOBase.readinto() methods. (Contributed by Nikolaus Rath in .)

    ipaddress

    Both the and IPv6Network classes now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses:

    1. >>> import ipaddress
    2. >>> ipaddress.IPv4Network(('127.0.0.0', 8))
    3. IPv4Network('127.0.0.0/8')
    4. >>> ipaddress.IPv4Network(('127.0.0.0', '255.0.0.0'))
    5. IPv4Network('127.0.0.0/8')

    （由 Peter Moody 和 Antoine Pitrou 在 中贡献。）

    A new reverse_pointer attribute for the IPv4Network and classes returns the name of the reverse DNS PTR record:

    1. >>> import ipaddress
    2. >>> addr = ipaddress.IPv4Address('127.0.0.1')
    3. >>> addr.reverse_pointer
    4. '1.0.0.127.in-addr.arpa'
    5. >>> addr6 = ipaddress.IPv6Address('::1')
    6. >>> addr6.reverse_pointer
    7. '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'

    （由 Leon Weber 在 bpo-20480 中贡献。）

    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 .)

    JSON decoder now raises JSONDecodeError instead of 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 . 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:

    1. >>> import locale
    2. >>> locale.setlocale(locale.LC_NUMERIC, 'de_DE.UTF-8')
    3. 'de_DE.UTF-8'
    4. >>> locale.delocalize('1.234,56')
    5. '1234.56'
    6. >>> locale.setlocale(locale.LC_NUMERIC, 'en_US.UTF-8')
    7. 'en_US.UTF-8'
    8. >>> locale.delocalize('1,234.56')
    9. '1234.56'

    （由 Cédric Krier 在 中贡献。）

    logging

    All logging methods ( log(), , critical(), , etc.), now accept exception instances as an exc_info argument, in addition to boolean values and exception tuples:

    1. >>> import logging
    2. >>> try:
    3. ...     1/0
    4. ... except ZeroDivisionError as ex:
    5. ...     logging.error('exception', exc_info=ex)
    6. ERROR:root:exception

    （由 Yury Selivanov 在 bpo-20537 中贡献。）

    The class now accepts an optional ssl.SSLContext instance to configure SSL settings used in an HTTP connection. (Contributed by Alex Gaynor in .)

    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 .)

    math

    Two new constants have been added to the module: inf and . (Contributed by Mark Dickinson in bpo-23185.)

    A new function provides a way to test for approximate equality. (Contributed by Chris Barker and Tal Einat in bpo-24270.)

    A new function has been added. The fractions.gcd() function is now deprecated. (Contributed by Mark Dickinson and Serhiy Storchaka in .)

    multiprocessing

    objects now support the context manager protocol. (Contributed by Charles-François Natali in .)

    operator

    , itemgetter(), and objects now support pickling. (Contributed by Josh Rosenberg and Serhiy Storchaka in bpo-22955.)

    New and imatmul() functions to perform matrix multiplication. (Contributed by Benjamin Peterson in .)

    os

    The new function returning an iterator of DirEntry objects has been added. If possible, 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 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 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 and set_blocking() functions allow getting and setting a file descriptor’s blocking mode (.) (Contributed by Victor Stinner in bpo-22054.)

    The and ftruncate() functions are now supported on Windows. (Contributed by Steve Dower in .)

    There is a new os.path.commonpath() function returning the longest common sub-path of each passed pathname. Unlike the function, it always returns a valid path:

    1. >>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
    2. '/usr/l'
    4. >>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
    5. '/usr'

    （由 Rafik Draoui 和 Serhiy Storchaka 在 bpo-10395 中贡献。）

    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 object, or a string:

    1. >>> import pathlib
    2. >>> p1 = pathlib.Path('/etc/hosts')
    3. >>> p2 = pathlib.Path('/etc/../etc/hosts')
    4. >>> p1.samefile(p2)
    5. True

    （由 Vajrasky Kok 和 Antoine Pitrou 在 bpo-19775 中贡献。）

    The method now accepts a new optional exist_ok argument to match mkdir -p and os.makedirs() functionality. (Contributed by Berker Peksag in .)

    There is a new Path.expanduser() method to expand ~ and ~user prefixes. (Contributed by Serhiy Storchaka and Claudiu Popa in .)

    A new Path.home() class method can be used to get a instance representing the user’s home directory. (Contributed by Victor Salgado and Mayank Tripathi in bpo-19777.)

    New , Path.read_text(), , Path.read_bytes() methods to simplify read/write operations on files.

    The following code snippet will create or rewrite existing file :

    1. >>> import pathlib
    2. >>> p = pathlib.Path('~/spam42')
    3. >>> p.expanduser().write_text('ham')
    4. 3

    （由 Christopher Welborn 在 中贡献。）

    pickle

    Nested objects, such as unbound methods or nested classes, can now be pickled using 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 (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:

    1. >>> import re
    2. >>> pat = re.compile(r'(a|b).(?<=\1)c')
    3. >>> pat.match('aac')
    4. <_sre.SRE_Match object; span=(0, 3), match='aac'>
    5. >>> pat.match('bbc')
    6. <_sre.SRE_Match object; span=(0, 3), match='bbc'>

    （由 Serhiy Storchaka 在 bpo-9179 中贡献。）

    The number of capturing groups in regular expressions is no longer limited to 100. (Contributed by Serhiy Storchaka in .)

    The sub() and functions now replace unmatched groups with empty strings instead of raising an exception. (Contributed by Serhiy Storchaka in bpo-1519638.)

    The exceptions have new attributes, msg, , pos, , and colno, that provide better context information about the error:

    1. >>> re.compile("""
    2. ...     (?x)
    3. ...     .++
    4. ... """)
    5. Traceback (most recent call last):
    6.    ...
    7. sre_constants.error: multiple repeat at position 16 (line 3, column 7)

    （由 Serhiy Storchaka 在 中贡献。）

    readline

    A new 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 .)

    shutil

    The function now accepts a copy_function argument, allowing, for example, the copy() function to be used instead of the default if there is a need to ignore file metadata when moving. (Contributed by Claudiu Popa in bpo-19840.)

    The 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 .)

    Various SIG* constants in the signal module have been converted into . 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 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 .)

    The SMTPServer class now advertises the 8BITMIME extension () 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 .)

    The SMTPServer class now also supports the SMTPUTF8 extension (: 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 .)

    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 .)

    A new SMTP.auth() method provides a convenient way to implement custom authentication mechanisms. (Contributed by Milan Oberkirch in .)

    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 .)

    Both the SMTP.sendmail() and methods now support RFC 6531 (SMTPUTF8). (Contributed by Milan Oberkirch and R. David Murray in .)

    sndhdr

    The and whathdr() functions now return a . (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 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 . (Contributed by Giampaolo Rodola’ in bpo-17552.)

    The 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 method is now optional. By default it is set to SOMAXCONN or to 128, whichever is less. (Contributed by Charles-François Natali in .)

    ssl

    内存 BIO 支持

    （由 Geert Jansen 在 bpo-21965 中贡献。）

    The new 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 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 method can be used to create a new SSLObject instance.

    Application-Layer Protocol Negotiation Support

    （由 Benjamin Peterson 在 中贡献。）

    Where OpenSSL support is present, the ssl module now implements the Application-Layer Protocol Negotiation TLS extension as described in .

    The new SSLContext.set_alpn_protocols() can be used to specify which protocols a socket should advertise during the TLS handshake.

    Other Changes

    There is a new SSLSocket.version() method to query the actual protocol version in use. (Contributed by Antoine Pitrou in .)

    The SSLSocket class now implements a SSLSocket.sendfile() method. (Contributed by Giampaolo Rodola’ in .)

    The SSLSocket.send() method now raises either the ssl.SSLWantReadError or exception on a non-blocking socket if the operation would block. Previously, it would return 0. (Contributed by Nikolaus Rath in bpo-20951.)

    The function now interprets the input time as UTC and not as local time, per RFC 5280. Additionally, the return value is always an . (Contributed by Akira Li in bpo-19940.)

    New SSLObject.shared_ciphers() and methods return the list of ciphers sent by the client during the handshake. (Contributed by Benjamin Peterson in bpo-23186.)

    The , SSLSocket.read(), SSLSocket.shutdown(), and 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 .)

    The match_hostname() function now supports matching of IP addresses. (Contributed by Antoine Pitrou in .)

    sqlite3

    The class now fully supports the sequence protocol, in particular reversed() iteration and slice indexing. (Contributed by Claudiu Popa in ; 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 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.)

    示例:

    1. >>> subprocess.run(["ls", "-l"])  # doesn't capture output
    2. CompletedProcess(args=['ls', '-l'], returncode=0)
    4. >>> subprocess.run("exit 1", shell=True, check=True)
    5. Traceback (most recent call last):
    6.   ...
    7. subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1
    9. >>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
    10. CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
    11. 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 is created by an async def function. A corresponding 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 .)

    A new is_finalizing() function can be used to check if the Python interpreter is . (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 .)

    The TarFile.extractall() and 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 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 .)

    threading

    Both the and RLock.acquire() methods now use a monotonic clock for timeout management. (Contributed by Victor Stinner in .)

    time

    The 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 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.)

    回溯

    New walk_stack() and functions to conveniently traverse frame and traceback objects. (Contributed by Robert Collins in bpo-17911.)

    New lightweight classes: , StackSummary, and . (Contributed by Robert Collins in bpo-17911.)

    Both the and print_stack() functions now support negative values for the limit argument. (Contributed by Dmitry Kazakov in .)

    types

    A new function to transform generator and objects into awaitables. (Contributed by Yury Selivanov in .)

    A new type called CoroutineType, which is used for objects created by async def functions. (Contributed by Yury Selivanov in .)

    unicodedata

    The 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 .)

    Unittest discovery errors now are exposed in the TestLoader.errors attribute of the 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 .)

    unittest.mock

    The 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 .)

    • A new Mock.assert_not_called() method to check if the mock object was called. (Contributed by Kushal Das in .)

    The MagicMock class now supports , __divmod__() and operators. (Contributed by Johannes Baiter in bpo-20968, and Håkan Lövdahl in and bpo-23568.)

    It is no longer necessary to explicitly pass create=True to the 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 and Akshit Khurana in bpo-7159.)

    A new quote_via argument for the function provides a way to control the encoding of query parts if needed. (Contributed by Samwyse and Arnon Yaari in bpo-13866.)

    The function accepts an ssl.SSLContext object as a context argument, which will be used for the HTTPS connection. (Contributed by Alex Gaynor in .)

    The parse.urljoin() was updated to use the semantics for the resolution of relative URLs, rather than RFC 1808 and . (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 .)

    xmlrpc

    The class now supports the context manager protocol. (Contributed by Claudiu Popa in .)

    The client.ServerProxy constructor now accepts an optional 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 .)

    parseString() now accepts a 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 method now accepts "x" to request exclusive creation. (Contributed by Serhiy Storchaka in bpo-21717.)

    其他模块级更改

    Many functions in the mmap, , socket, , and codecs modules now accept writable . (Contributed by Serhiy Storchaka in bpo-23001.)

    性能优化

    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 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 .)

    Some operations on ipaddress and IPv6Network have been massively sped up, such as , supernet(), , collapse_addresses(). The speed up can range from 3 to 15 times. (Contributed by Antoine Pitrou, Michel Albert, and Markus in , bpo-21487, , bpo-23266.)

    Pickling of objects was optimized to produce significantly smaller output. (Contributed by Serhiy Storchaka in bpo-23133.)

    Many operations on are now 50% to 100% faster. (Contributed by Serhiy Storchaka in bpo-15381 and David Wilson in .)

    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 and bpo-23344.)

    The UTF-32 encoder is now 3 to 7 times faster. (Contributed by Serhiy Storchaka in .)

    Regular expressions are now parsed up to 10% faster. (Contributed by Serhiy Storchaka in bpo-19380.)

    The function was optimized to run with ensure_ascii=False as fast as with ensure_ascii=True. (Contributed by Naoki Inada in bpo-23206.)

    The and PyObject_IsSubclass() functions have been sped up in the common case that the second argument has 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 .)

    Objects from the random module now use 50% less memory on 64-bit builds. (Contributed by Serhiy Storchaka in .)

    The property() getter calls are up to 25% faster. (Contributed by Joe Jevnik in .)

    Instantiation of fractions.Fraction is now up to 30% faster. (Contributed by Stefan Behnel in .)

    String methods find(), , split(), and the in string operator are now significantly faster for searching 1-character substrings. (Contributed by Serhiy Storchaka in .)

    构建和 C API 的改变

    增加了 calloc 函数

    (Victor Stinner 贡献于 bpo-21233.)

    新的 encoding/decoding 帮助函数:

    （由 Victor Stinner 在 中贡献。）

    A new PyCodec_NameReplaceErrors() function to replace the unicode encode error with \N{...} escapes. (Contributed by Serhiy Storchaka in .)

    A new PyErr_FormatV() function similar to , but accepts a va_list argument. (Contributed by Antoine Pitrou in bpo-18711.)

    A new PyExc_RecursionError exception. (Contributed by Georg Brandl in .)

    New PyModule_FromDefAndSpec(), , and PyModule_ExecDef() functions introduced by – multi-phase extension module initialization. (Contributed by Petr Viktorin in bpo-24268.)

    New and PyNumber_InPlaceMatrixMultiply() functions to perform matrix multiplication. (Contributed by Benjamin Peterson in . See also PEP 465 for details.)

    The 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 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.

    新关键字

    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.

    已弃用的 Python 行为

    Raising the StopIteration exception inside a generator will now generate a silent , which will become a non-silent deprecation warning in Python 3.6 and will trigger a RuntimeError in Python 3.7. See for details.

    不支持的操作系统

    Windows XP is no longer supported by Microsoft, thus, per , CPython 3.5 is no longer officially supported on this OS.

    已弃用的 Python 模块、函数和方法

    The 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 .

    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 . 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, and coded_value of objects is deprecated. Use the set() method instead. In addition, the undocumented LegalChars parameter of is deprecated, and is now ignored.

    Passing a format string as keyword argument format_string to the format() method of the class has been deprecated. (Contributed by Serhiy Storchaka in bpo-23671.)

    The 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 .)

    The previously undocumented from_function and from_builtin methods of inspect.Signature are deprecated. Use the new method instead. (Contributed by Yury Selivanov in bpo-24248.)

    The function is deprecated and scheduled to be removed in Python 3.6. (See bpo-20438 for details.)

    The getfullargspec(), , and formatargspec() functions are deprecated in favor of the API. (Contributed by Yury Selivanov in bpo-20438.)

    and formatargvalues() functions were inadvertently marked as deprecated with the release of Python 3.5.0.

    Use of flag with str patterns or re.ASCII is now deprecated. (Contributed by Serhiy Storchaka in .)

    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 method now is deprecated and ignored. (Contributed by Robert Collins and Barry A. Warsaw in bpo-16662.)

    移除

    API 与特性的移除

    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 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 module was deprecated in 3.4.4 and is now removed. (Contributed by A. Jesse Jiryu Davis in bpo-23464.)

    移植到Python 3.5

    本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

    Python 行为的改变

    • 由于一个疏忽，之前的 Python 版本会错误地接受以下语法:

      Python 3.5 now correctly raises a , as generator expressions must be put in parentheses if not a sole argument to a function.

    更改的Python API

    • : 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 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 either or ssl.SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. (Contributed by Nikolaus Rath in .)

    • 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 bpo-21205.)

    • The deprecated “strict” mode and argument of , HTMLParser.error(), and the HTMLParserError exception have been removed. (Contributed by Ezio Melotti in bpo-15114.) The convert_charrefs argument of is now True 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 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 will no longer be raised and instead find_spec() will return None without caching None in , which is different than the typical case (bpo-22834).

    • HTTP status code and messages from and http.server were refactored into a common enum. The values in http.client and remain available for backwards compatibility. (Contributed by Demian Brecht in bpo-21793.)

    • When an import loader defines importlib.machinery.Loader.exec_module() it is now expected to also define create_module() (raises a now, will be an error in Python 3.6). If the loader inherits from importlib.abc.Loader then there is nothing to do, else simply define create_module() to return None. (Contributed by Brett Cannon in .)

    • The re.split() function always ignored empty pattern matches, so the "x*" pattern worked the same as "x+", and the "\b" pattern never worked. Now 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 dict-like interface has been made self consistent: morsel comparison now takes the key and into account, copy() now results in a instance rather than a dict, and will now raise an exception if any of the keys in the update dictionary are invalid. In addition, the undocumented LegalChars parameter of set() is deprecated and is now ignored. (Contributed by Demian Brecht in .)

    • PEP 488 has removed .pyo files from Python and introduced the optional opt- tag in .pyc file names. The 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 socket module now exports the 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 . Additionally, the return value is always an int. (Contributed by Akira Li in .)

    • The pygettext.py Tool now uses the standard +NNNN format for timezones in the POT-Creation-Date header.

    • The smtplib module now uses instead of the previous module-level 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 str.startswith() and methods no longer return True when finding the empty string and the indexes are completely out of range. (Contributed by Serhiy Storchaka in bpo-24284.)

    • The 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 pydoc module and the function. (Contributed by Serhiy Storchaka in bpo-15582.)

    • Nested calls are now flattened. If you were relying on the previous behavior, you can now either add an attribute to a functools.partial() object or you can create a subclass of . (Contributed by Alexander Belopolsky in bpo-7830.)

    C API 中的改变

    • The undocumented format member of the (non-public) PyMemoryViewObject structure has been removed. All extensions relying on the relevant parts in memoryobject.h must be rebuilt.

    • The PyMemAllocator structure was renamed to PyMemAllocatorEx and a new calloc field was added.

    • Removed non-documented macro PyObject_REPR which leaked references. Use format character %R in -like functions to format the repr() of the object. (Contributed by Serhiy Storchaka in .)

    • As part of the PEP 492 implementation, the tp_reserved slot of was replaced with a tp_as_async slot. Refer to for new types, structures and functions.

    Python 3.5.4 的显著变化

    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.

    （由 Victor Stinner 在 中贡献。）

    3.5.4 新版功能.

    Removal of make touch build target

    The 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.

    （由 Victor Stinner 在 中贡献。）

    在 3.5.4 版更改.