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| Editors: | Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io> |
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This article explains the new features in Python 3.6, compared to 3.5. Python 3.6 was released on December 23, 2016. See the changelog for a full list of changes.
See also
PEP 494 - Python 3.6 Release Schedule
New syntax features:
New library modules:
CPython implementation improvements:
**kwargs now
corresponds to the order in which keyword
arguments were passed to the function.Significant improvements in the standard library:
asyncio module has received new features, significant
usability and performance improvements, and a fair amount of bug fixes.
Starting with Python 3.6 the asyncio module is no longer provisional
and its API is considered stable.datetime module has gained support for
Local Time Disambiguation.typing module received a number of
improvements.tracemalloc module has been significantly reworked
and is now used to provide better output for ResourceWarning
as well as provide better diagnostics for memory allocation errors.
See the PYTHONMALLOC section for more
information.Security improvements:
secrets module has been added to simplify the generation of
cryptographically strong pseudo-random numbers suitable for
managing secrets such as account authentication, tokens, and similar.os.urandom() now blocks until the system urandom entropy
pool is initialized to increase the security. See the PEP 524 for the
rationale.hashlib and ssl modules now support OpenSSL 1.1.0.ssl module have been
improved.hashlib module received support for the BLAKE2, SHA-3 and SHAKE
hash algorithms and the scrypt() key derivation function.Windows improvements:
py.exe launcher, when used interactively, no longer prefers
Python 2 over Python 3 when the user doesn’t specify a version (via
command line arguments or a config file). Handling of shebang lines
remains unchanged - “python” refers to Python 2 in that case.python.exe and pythonw.exe have been marked as long-path aware,
which means that the 260 character path limit may no longer apply.
See removing the MAX_PATH limitation for details.._pth file can be added to force isolated mode and fully specify
all search paths to avoid registry and environment lookup. See
the documentation for more information.python36.zip file now works as a landmark to infer
PYTHONHOME. See the documentation for
more information.PEP 498 introduces a new kind of string literals: f-strings, or formatted string literals.
Formatted string literals are prefixed with 'f' and are similar to
the format strings accepted by str.format(). They contain replacement
fields surrounded by curly braces. The replacement fields are expressions,
which are evaluated at run time, and then formatted using the
format() protocol:
>>> name = "Fred"
>>> f"He said his name is {name}."
'He said his name is Fred.'
>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal("12.34567")
>>> f"result: {value:{width}.{precision}}" # nested fields
'result: 12.35'
See also
PEP 484 introduced the standard for type annotations of function parameters, a.k.a. type hints. This PEP adds syntax to Python for annotating the types of variables including class variables and instance variables:
primes: List[int] = []
captain: str # Note: no initial value!
class Starship:
stats: Dict[str, int] = {}
Just as for function annotations, the Python interpreter does not attach any
particular meaning to variable annotations and only stores them in the
__annotations__ attribute of a class or module.
In contrast to variable declarations in statically typed languages,
the goal of annotation syntax is to provide an easy way to specify structured
type metadata for third party tools and libraries via the abstract syntax tree
and the __annotations__ attribute.
PEP 515 adds the ability to use underscores in numeric literals for improved readability. For example:
>>> 1_000_000_000_000_000
1000000000000000
>>> 0x_FF_FF_FF_FF
4294967295
Single underscores are allowed between digits and after any base specifier. Leading, trailing, or multiple underscores in a row are not allowed.
The string formatting language also now has support
for the '_' option to signal the use of an underscore for a thousands
separator for floating point presentation types and for integer
presentation type 'd'. For integer presentation types 'b',
'o', 'x', and 'X', underscores will be inserted every 4
digits:
>>> '{:_}'.format(1000000)
'1_000_000'
>>> '{:_x}'.format(0xFFFFFFFF)
'ffff_ffff'
See also
PEP 492 introduced support for native coroutines and async / await
syntax to Python 3.5. A notable limitation of the Python 3.5 implementation
is that it was not possible to use await and yield in the same
function body. In Python 3.6 this restriction has been lifted, making it
possible to define asynchronous generators:
async def ticker(delay, to):
"""Yield numbers from 0 to *to* every *delay* seconds."""
for i in range(to):
yield i
await asyncio.sleep(delay)
The new syntax allows for faster and more concise code.
See also
PEP 530 adds support for using async for in list, set, dict
comprehensions and generator expressions:
result = [i async for i in aiter() if i % 2]
Additionally, await expressions are supported in all kinds
of comprehensions:
result = [await fun() for fun in funcs if await condition()]
See also
It is now possible to customize subclass creation without using a metaclass.
The new __init_subclass__ classmethod will be called on the base class
whenever a new subclass is created:
class PluginBase:
subclasses = []
def __init_subclass__(cls, **kwargs):
super().__init_subclass__(**kwargs)
cls.subclasses.append(cls)
class Plugin1(PluginBase):
pass
class Plugin2(PluginBase):
pass
In order to allow zero-argument super() calls to work correctly from
__init_subclass__() implementations, custom metaclasses must
ensure that the new __classcell__ namespace entry is propagated to
type.__new__ (as described in Creating the class object).
See also
PEP 487 extends the descriptor protocol to include the new optional
__set_name__() method. Whenever a new class is defined, the new
method will be called on all descriptors included in the definition, providing
them with a reference to the class being defined and the name given to the
descriptor within the class namespace. In other words, instances of
descriptors can now know the attribute name of the descriptor in the
owner class:
class IntField:
def __get__(self, instance, owner):
return instance.__dict__[self.name]
def __set__(self, instance, value):
if not isinstance(value, int):
raise ValueError(f'expecting integer in {self.name}')
instance.__dict__[self.name] = value
# this is the new initializer:
def __set_name__(self, owner, name):
self.name = name
class Model:
int_field = IntField()
See also
File system paths have historically been represented as str
or bytes objects. This has led to people who write code which
operate on file system paths to assume that such objects are only one
of those two types (an int representing a file descriptor
does not count as that is not a file path). Unfortunately that
assumption prevents alternative object representations of file system
paths like pathlib from working with pre-existing code,
including Python’s standard library.
To fix this situation, a new interface represented by
os.PathLike has been defined. By implementing the
__fspath__() method, an object signals that it
represents a path. An object can then provide a low-level
representation of a file system path as a str or
bytes object. This means an object is considered
path-like if it implements
os.PathLike or is a str or bytes object
which represents a file system path. Code can use os.fspath(),
os.fsdecode(), or os.fsencode() to explicitly get a
str and/or bytes representation of a path-like
object.
The built-in open() function has been updated to accept
os.PathLike objects, as have all relevant functions in the
os and os.path modules, and most other functions and
classes in the standard library. The os.DirEntry class
and relevant classes in pathlib have also been updated to
implement os.PathLike.
The hope is that updating the fundamental functions for operating
on file system paths will lead to third-party code to implicitly
support all path-like objects without any
code changes, or at least very minimal ones (e.g. calling
os.fspath() at the beginning of code before operating on a
path-like object).
Here are some examples of how the new interface allows for
pathlib.Path to be used more easily and transparently with
pre-existing code:
>>> import pathlib
>>> with open(pathlib.Path("README")) as f:
... contents = f.read()
...
>>> import os.path
>>> os.path.splitext(pathlib.Path("some_file.txt"))
('some_file', '.txt')
>>> os.path.join("/a/b", pathlib.Path("c"))
'/a/b/c'
>>> import os
>>> os.fspath(pathlib.Path("some_file.txt"))
'some_file.txt'
(Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.)
See also
In most world locations, there have been and will be times when local clocks are moved back. In those times, intervals are introduced in which local clocks show the same time twice in the same day. In these situations, the information displayed on a local clock (or stored in a Python datetime instance) is insufficient to identify a particular moment in time.
PEP 495 adds the new fold attribute to instances of
datetime.datetime and datetime.time classes to differentiate
between two moments in time for which local times are the same:
>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
... u = u0 + i*HOUR
... t = u.astimezone(Eastern)
... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
The values of the fold attribute have the
value 0 for all instances except those that represent the second
(chronologically) moment in time in an ambiguous case.
See also
Representing filesystem paths is best performed with str (Unicode) rather than bytes. However, there are some situations where using bytes is sufficient and correct.
Prior to Python 3.6, data loss could result when using bytes paths on Windows.
With this change, using bytes to represent paths is now supported on Windows,
provided those bytes are encoded with the encoding returned by
sys.getfilesystemencoding(), which now defaults to 'utf-8'.
Applications that do not use str to represent paths should use
os.fsencode() and os.fsdecode() to ensure their bytes are
correctly encoded. To revert to the previous behaviour, set
PYTHONLEGACYWINDOWSFSENCODING or call
sys._enablelegacywindowsfsencoding().
See PEP 529 for more information and discussion of code modifications that may be required.
The default console on Windows will now accept all Unicode characters and
provide correctly read str objects to Python code. sys.stdin,
sys.stdout and sys.stderr now default to utf-8 encoding.
This change only applies when using an interactive console, and not when
redirecting files or pipes. To revert to the previous behaviour for interactive
console use, set PYTHONLEGACYWINDOWSIOENCODING.
See also
Attributes in a class definition body have a natural ordering: the same
order in which the names appear in the source. This order is now
preserved in the new class’s __dict__ attribute.
Also, the effective default class execution namespace (returned from type.__prepare__()) is now an insertion-order-preserving mapping.
See also
**kwargs in a function signature is now guaranteed to be an
insertion-order-preserving mapping.
See also
The dict type now uses a “compact” representation
based on a proposal by Raymond Hettinger
which was first implemented by PyPy.
The memory usage of the new dict() is between 20% and 25% smaller
compared to Python 3.5.
The order-preserving aspect of this new implementation is considered an implementation detail and should not be relied upon (this may change in the future, but it is desired to have this new dict implementation in the language for a few releases before changing the language spec to mandate order-preserving semantics for all current and future Python implementations; this also helps preserve backwards-compatibility with older versions of the language where random iteration order is still in effect, e.g. Python 3.5).
(Contributed by INADA Naoki in bpo-27350. Idea originally suggested by Raymond Hettinger.)
While Python provides extensive support to customize how code executes, one place it has not done so is in the evaluation of frame objects. If you wanted some way to intercept frame evaluation in Python there really wasn’t any way without directly manipulating function pointers for defined functions.
PEP 523 changes this by providing an API to make frame evaluation pluggable at the C level. This will allow for tools such as debuggers and JITs to intercept frame evaluation before the execution of Python code begins. This enables the use of alternative evaluation implementations for Python code, tracking frame evaluation, etc.
This API is not part of the limited C API and is marked as private to signal that usage of this API is expected to be limited and only applicable to very select, low-level use-cases. Semantics of the API will change with Python as necessary.
See also
The new PYTHONMALLOC environment variable allows setting the Python
memory allocators and installing debug hooks.
It is now possible to install debug hooks on Python memory allocators on Python
compiled in release mode using PYTHONMALLOC=debug. Effects of debug hooks:
0xCB0xDBPyObject_Free() called on a memory block allocated by
PyMem_Malloc().PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) and
PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) domains are called.Checking if the GIL is held is also a new feature of Python 3.6.
See the PyMem_SetupDebugHooks() function for debug hooks on Python
memory allocators.
It is now also possible to force the usage of the malloc() allocator of
the C library for all Python memory allocations using PYTHONMALLOC=malloc.
This is helpful when using external memory debuggers like Valgrind on
a Python compiled in release mode.
On error, the debug hooks on Python memory allocators now use the
tracemalloc module to get the traceback where a memory block was
allocated.
Example of fatal error on buffer overflow using
python3.6 -X tracemalloc=5 (store 5 frames in traces):
Debug memory block at address p=0x7fbcd41666f8: API 'o'
4 bytes originally requested
The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
at tail+0: 0x02 *** OUCH
at tail+1: 0xfb
at tail+2: 0xfb
at tail+3: 0xfb
at tail+4: 0xfb
at tail+5: 0xfb
at tail+6: 0xfb
at tail+7: 0xfb
The block was made by call #1233329 to debug malloc/realloc.
Data at p: 1a 2b 30 00
Memory block allocated at (most recent call first):
File "test/test_bytes.py", line 323
File "unittest/case.py", line 600
File "unittest/case.py", line 648
File "unittest/suite.py", line 122
File "unittest/suite.py", line 84
Fatal Python error: bad trailing pad byte
Current thread 0x00007fbcdbd32700 (most recent call first):
File "test/test_bytes.py", line 323 in test_hex
File "unittest/case.py", line 600 in run
File "unittest/case.py", line 648 in __call__
File "unittest/suite.py", line 122 in run
File "unittest/suite.py", line 84 in __call__
File "unittest/suite.py", line 122 in run
File "unittest/suite.py", line 84 in __call__
...
Python can now be built --with-dtrace which enables static markers
for the following events in the interpreter:
This can be used to instrument running interpreters in production, without the need to recompile specific debug builds or providing application-specific profiling/debugging code.
More details in Instrumenting CPython with DTrace and SystemTap.
The current implementation is tested on Linux and macOS. Additional markers may be added in the future.
(Contributed by Łukasz Langa in bpo-21590, based on patches by Jesús Cea Avión, David Malcolm, and Nikhil Benesch.)
Some smaller changes made to the core Python language are:
global or nonlocal statement must now textually appear
before the first use of the affected name in the same scope.
Previously this was a SyntaxWarning.None to indicate that the corresponding operation is not available.
For example, if a class sets __iter__() to None, the class
is not iterable.
(Contributed by Andrew Barnert and Ivan Levkivskyi in bpo-25958.)"[Previous line repeated {count} more times]" (see
traceback for an example).
(Contributed by Emanuel Barry in bpo-26823.)ModuleNotFoundError
(subclass of ImportError) when it cannot find a module. Code
that currently checks for ImportError (in try-except) will still work.
(Contributed by Eric Snow in bpo-15767.)super() will now work correctly
when called from metaclass methods during class creation.
(Contributed by Martin Teichmann in bpo-23722.)The main purpose of the new secrets module is to provide an obvious way
to reliably generate cryptographically strong pseudo-random values suitable
for managing secrets, such as account authentication, tokens, and similar.
Warning
Note that the pseudo-random generators in the random module
should NOT be used for security purposes. Use secrets
on Python 3.6+ and os.urandom() on Python 3.5 and earlier.
See also
Exhausted iterators of array.array will now stay exhausted even
if the iterated array is extended. This is consistent with the behavior
of other mutable sequences.
Contributed by Serhiy Storchaka in bpo-26492.
The new ast.Constant AST node has been added. It can be used
by external AST optimizers for the purposes of constant folding.
Contributed by Victor Stinner in bpo-26146.
Starting with Python 3.6 the asyncio module is no longer provisional and its
API is considered stable.
Notable changes in the asyncio module since Python 3.5.0
(all backported to 3.5.x due to the provisional status):
get_event_loop() function has been changed to
always return the currently running loop when called from couroutines
and callbacks.
(Contributed by Yury Selivanov in bpo-28613.)ensure_future() function and all functions that
use it, such as loop.run_until_complete(),
now accept all kinds of awaitable objects.
(Contributed by Yury Selivanov.)run_coroutine_threadsafe() function to submit
coroutines to event loops from other threads.
(Contributed by Vincent Michel.)Transport.is_closing()
method to check if the transport is closing or closed.
(Contributed by Yury Selivanov.)loop.create_server()
method can now accept a list of hosts.
(Contributed by Yann Sionneau.)loop.create_future()
method to create Future objects. This allows alternative event
loop implementations, such as
uvloop, to provide a faster
asyncio.Future implementation.
(Contributed by Yury Selivanov in bpo-27041.)loop.get_exception_handler()
method to get the current exception handler.
(Contributed by Yury Selivanov in bpo-27040.)StreamReader.readuntil()
method to read data from the stream until a separator bytes
sequence appears.
(Contributed by Mark Korenberg.)StreamReader.readexactly()
has been improved.
(Contributed by Mark Korenberg in bpo-28370.)loop.getaddrinfo()
method is optimized to avoid calling the system getaddrinfo
function if the address is already resolved.
(Contributed by A. Jesse Jiryu Davis.)loop.stop()
method has been changed to stop the loop immediately after
the current iteration. Any new callbacks scheduled as a result
of the last iteration will be discarded.
(Contributed by Guido van Rossum in bpo-25593.)Future.set_exception
will now raise TypeError when passed an instance of
the StopIteration exception.
(Contributed by Chris Angelico in bpo-26221.)loop.connect_accepted_socket()
method to be used by servers that accept connections outside of asyncio,
but that use asyncio to handle them.
(Contributed by Jim Fulton in bpo-27392.)TCP_NODELAY flag is now set for all TCP transports by default.
(Contributed by Yury Selivanov in bpo-27456.)loop.shutdown_asyncgens()
to properly close pending asynchronous generators before closing the
loop.
(Contributed by Yury Selivanov in bpo-28003.)Future and Task
classes now have an optimized C implementation which makes asyncio
code up to 30% faster.
(Contributed by Yury Selivanov and INADA Naoki in bpo-26081
and bpo-28544.)The b2a_base64() function now accepts an optional newline
keyword argument to control whether the newline character is appended to the
return value.
(Contributed by Victor Stinner in bpo-25357.)
The new cmath.tau (τ) constant has been added.
(Contributed by Lisa Roach in bpo-12345, see PEP 628 for details.)
New constants: cmath.inf and cmath.nan to
match math.inf and math.nan, and also cmath.infj
and cmath.nanj to match the format used by complex repr.
(Contributed by Mark Dickinson in bpo-23229.)
The new Collection abstract base class has been
added to represent sized iterable container classes.
(Contributed by Ivan Levkivskyi, docs by Neil Girdhar in bpo-27598.)
The new Reversible abstract base class represents
iterable classes that also provide the __reversed__() method.
(Contributed by Ivan Levkivskyi in bpo-25987.)
The new AsyncGenerator abstract base class represents
asynchronous generators.
(Contributed by Yury Selivanov in bpo-28720.)
The namedtuple() function now accepts an optional
keyword argument module, which, when specified, is used for
the __module__ attribute of the returned named tuple class.
(Contributed by Raymond Hettinger in bpo-17941.)
The verbose and rename arguments for
namedtuple() are now keyword-only.
(Contributed by Raymond Hettinger in bpo-25628.)
Recursive collections.deque instances can now be pickled.
(Contributed by Serhiy Storchaka in bpo-26482.)
The ThreadPoolExecutor
class constructor now accepts an optional thread_name_prefix argument
to make it possible to customize the names of the threads created by the
pool.
(Contributed by Gregory P. Smith in bpo-27664.)
The contextlib.AbstractContextManager class has been added to
provide an abstract base class for context managers. It provides a
sensible default implementation for __enter__() which returns
self and leaves __exit__() an abstract method. A matching
class has been added to the typing module as
typing.ContextManager.
(Contributed by Brett Cannon in bpo-25609.)
The datetime and time classes have
the new fold attribute used to disambiguate local time
when necessary. Many functions in the datetime have been
updated to support local time disambiguation.
See Local Time Disambiguation section for more
information.
(Contributed by Alexander Belopolsky in bpo-24773.)
The datetime.strftime() and
date.strftime() methods now support
ISO 8601 date directives %G, %u and %V.
(Contributed by Ashley Anderson in bpo-12006.)
The datetime.isoformat() function
now accepts an optional timespec argument that specifies the number
of additional components of the time value to include.
(Contributed by Alessandro Cucci and Alexander Belopolsky in bpo-19475.)
The datetime.combine() now
accepts an optional tzinfo argument.
(Contributed by Alexander Belopolsky in bpo-27661.)
New Decimal.as_integer_ratio()
method that returns a pair (n, d) of integers that represent the given
Decimal instance as a fraction, in lowest terms and
with a positive denominator:
>>> Decimal('-3.14').as_integer_ratio()
(-157, 50)
(Contributed by Stefan Krah amd Mark Dickinson in bpo-25928.)
The default_format attribute has been removed from
distutils.command.sdist.sdist and the formats
attribute defaults to ['gztar']. Although not anticipated,
any code relying on the presence of default_format may
need to be adapted. See bpo-27819 for more details.
The new email API, enabled via the policy keyword to various constructors, is
no longer provisional. The email documentation has been reorganized and
rewritten to focus on the new API, while retaining the old documentation for
the legacy API. (Contributed by R. David Murray in bpo-24277.)
The email.mime classes now all accept an optional policy keyword.
(Contributed by Berker Peksag in bpo-27331.)
The DecodedGenerator now supports the policy
keyword.
There is a new policy attribute,
message_factory, that controls what class is used
by default when the parser creates new message objects. For the
email.policy.compat32 policy this is Message,
for the new policies it is EmailMessage.
(Contributed by R. David Murray in bpo-20476.)
On Windows, added the 'oem' encoding to use CP_OEMCP, and the 'ansi'
alias for the existing 'mbcs' encoding, which uses the CP_ACP code page.
(Contributed by Steve Dower in bpo-27959.)
Two new enumeration base classes have been added to the enum module:
Flag and IntFlags. Both are used to define
constants that can be combined using the bitwise operators.
(Contributed by Ethan Furman in bpo-23591.)
Many standard library modules have been updated to use the
IntFlags class for their constants.
The new enum.auto value can be used to assign values to enum
members automatically:
>>> from enum import Enum, auto
>>> class Color(Enum):
... red = auto()
... blue = auto()
... green = auto()
...
>>> list(Color)
[<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>]
On Windows, the faulthandler module now installs a handler for Windows
exceptions: see faulthandler.enable(). (Contributed by Victor Stinner in
bpo-23848.)
hook_encoded() now supports the errors argument.
(Contributed by Joseph Hackman in bpo-25788.)
hashlib supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.
(Contributed by Christian Heimes in bpo-26470.)
BLAKE2 hash functions were added to the module. blake2b()
and blake2s() are always available and support the full
feature set of BLAKE2.
(Contributed by Christian Heimes in bpo-26798 based on code by
Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.)
The SHA-3 hash functions sha3_224(), sha3_256(),
sha3_384(), sha3_512(), and SHAKE hash functions
shake_128() and shake_256() were added.
(Contributed by Christian Heimes in bpo-16113. Keccak Code Package
by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and
Ronny Van Keer.)
The password-based key derivation function scrypt() is now
available with OpenSSL 1.1.0 and newer.
(Contributed by Christian Heimes in bpo-27928.)
HTTPConnection.request() and
endheaders() both now support
chunked encoding request bodies.
(Contributed by Demian Brecht and Rolf Krahl in bpo-12319.)
The idlelib package is being modernized and refactored to make IDLE look and work better and to make the code easier to understand, test, and improve. Part of making IDLE look better, especially on Linux and Mac, is using ttk widgets, mostly in the dialogs. As a result, IDLE no longer runs with tcl/tk 8.4. It now requires tcl/tk 8.5 or 8.6. We recommend running the latest release of either.
‘Modernizing’ includes renaming and consolidation of idlelib modules. The renaming of files with partial uppercase names is similar to the renaming of, for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0. As a result, imports of idlelib files that worked in 3.5 will usually not work in 3.6. At least a module name change will be needed (see idlelib/README.txt), sometimes more. (Name changes contributed by Al Swiegart and Terry Reedy in bpo-24225. Most idlelib patches since have been and will be part of the process.)
In compensation, the eventual result with be that some idlelib classes will be easier to use, with better APIs and docstrings explaining them. Additional useful information will be added to idlelib when available.
Import now raises the new exception ModuleNotFoundError
(subclass of ImportError) when it cannot find a module. Code
that current checks for ImportError (in try-except) will still work.
(Contributed by Eric Snow in bpo-15767.)
importlib.util.LazyLoader now calls
create_module() on the wrapped loader, removing the
restriction that importlib.machinery.BuiltinImporter and
importlib.machinery.ExtensionFileLoader couldn’t be used with
importlib.util.LazyLoader.
importlib.util.cache_from_source(),
importlib.util.source_from_cache(), and
importlib.util.spec_from_file_location() now accept a
path-like object.
The inspect.signature() function now reports the
implicit .0 parameters generated by the compiler for comprehension and
generator expression scopes as if they were positional-only parameters called
implicit0. (Contributed by Jelle Zijlstra in bpo-19611.)
To reduce code churn when upgrading from Python 2.7 and the legacy
inspect.getargspec() API, the previously documented deprecation of
inspect.getfullargspec() has been reversed. While this function is
convenient for single/source Python 2/3 code bases, the richer
inspect.signature() interface remains the recommended approach for new
code. (Contributed by Nick Coghlan in bpo-27172)
json.load() and json.loads() now support binary input. Encoded
JSON should be represented using either UTF-8, UTF-16, or UTF-32.
(Contributed by Serhiy Storchaka in bpo-17909.)
The new WatchedFileHandler.reopenIfNeeded()
method has been added to add the ability to check if the log file needs to
be reopened.
(Contributed by Marian Horban in bpo-24884.)
The tau (τ) constant has been added to the math and cmath
modules.
(Contributed by Lisa Roach in bpo-12345, see PEP 628 for details.)
Proxy Objects returned by
multiprocessing.Manager() can now be nested.
(Contributed by Davin Potts in bpo-6766.)
See the summary of PEP 519 for details on how the
os and os.path modules now support
path-like objects.
scandir() now supports bytes paths on Windows.
A new close() method allows explicitly closing a
scandir() iterator. The scandir() iterator now
supports the context manager protocol. If a scandir()
iterator is neither exhausted nor explicitly closed a ResourceWarning
will be emitted in its destructor.
(Contributed by Serhiy Storchaka in bpo-25994.)
On Linux, os.urandom() now blocks until the system urandom entropy pool
is initialized to increase the security. See the PEP 524 for the rationale.
The Linux getrandom() syscall (get random bytes) is now exposed as the new
os.getrandom() function.
(Contributed by Victor Stinner, part of the PEP 524)
pathlib now supports path-like objects.
(Contributed by Brett Cannon in bpo-27186.)
See the summary of PEP 519 for details.
The Pdb class constructor has a new optional readrc argument
to control whether .pdbrc files should be read.
Objects that need __new__ called with keyword arguments can now be pickled
using pickle protocols older than protocol version 4.
Protocol version 4 already supports this case. (Contributed by Serhiy
Storchaka in bpo-24164.)
pickletools.dis() now outputs the implicit memo index for the
MEMOIZE opcode.
(Contributed by Serhiy Storchaka in bpo-25382.)
The pydoc module has learned to respect the MANPAGER
environment variable.
(Contributed by Matthias Klose in bpo-8637.)
help() and pydoc can now list named tuple fields in the
order they were defined rather than alphabetically.
(Contributed by Raymond Hettinger in bpo-24879.)
The new choices() function returns a list of elements of
specified size from the given population with optional weights.
(Contributed by Raymond Hettinger in bpo-18844.)
Added support of modifier spans in regular expressions. Examples:
'(?i:p)ython' matches 'python' and 'Python', but not 'PYTHON';
'(?i)g(?-i:v)r' matches 'GvR' and 'gvr', but not 'GVR'.
(Contributed by Serhiy Storchaka in bpo-433028.)
Match object groups can be accessed by __getitem__, which is
equivalent to group(). So mo['name'] is now equivalent to
mo.group('name'). (Contributed by Eric Smith in bpo-24454.)
Match objects now support
index-like objects as group
indices.
(Contributed by Jeroen Demeyer and Xiang Zhang in bpo-27177.)
Added set_auto_history() to enable or disable
automatic addition of input to the history list. (Contributed by
Tyler Crompton in bpo-26870.)
Private and special attribute names now are omitted unless the prefix starts with underscores. A space or a colon is added after some completed keywords. (Contributed by Serhiy Storchaka in bpo-25011 and bpo-25209.)
The shlex has much
improved shell compatibility
through the new punctuation_chars argument to control which characters
are treated as punctuation.
(Contributed by Vinay Sajip in bpo-1521950.)
When specifying paths to add to sys.path in a .pth file,
you may now specify file paths on top of directories (e.g. zip files).
(Contributed by Wolfgang Langner in bpo-26587).
sqlite3.Cursor.lastrowid now supports the REPLACE statement.
(Contributed by Alex LordThorsen in bpo-16864.)
The ioctl() function now supports the
SIO_LOOPBACK_FAST_PATH control code.
(Contributed by Daniel Stokes in bpo-26536.)
The getsockopt() constants SO_DOMAIN,
SO_PROTOCOL, SO_PEERSEC, and SO_PASSSEC are now supported.
(Contributed by Christian Heimes in bpo-26907.)
The setsockopt() now supports the
setsockopt(level, optname, None, optlen: int) form.
(Contributed by Christian Heimes in bpo-27744.)
The socket module now supports the address family
AF_ALG to interface with Linux Kernel crypto API. ALG_*,
SOL_ALG and sendmsg_afalg() were added.
(Contributed by Christian Heimes in bpo-27744 with support from
Victor Stinner.)
New Linux constants TCP_USER_TIMEOUT and TCP_CONGESTION were added.
(Contributed by Omar Sandoval, issue:26273).
Servers based on the socketserver module, including those
defined in http.server, xmlrpc.server and
wsgiref.simple_server, now support the context manager
protocol.
(Contributed by Aviv Palivoda in bpo-26404.)
The wfile attribute of
StreamRequestHandler classes now implements
the io.BufferedIOBase writable interface. In particular,
calling write() is now guaranteed to send the
data in full. (Contributed by Martin Panter in bpo-26721.)
ssl supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.
(Contributed by Christian Heimes in bpo-26470.)
3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added. (Contributed by Christian Heimes in bpo-27850 and bpo-27766.)
SSLContext has better default configuration for options
and ciphers.
(Contributed by Christian Heimes in bpo-28043.)
SSL session can be copied from one client-side connection to another
with the new SSLSession class. TLS session resumption can
speed up the initial handshake, reduce latency and improve performance
(Contributed by Christian Heimes in bpo-19500 based on a draft by
Alex Warhawk.)
The new get_ciphers() method can be used to
get a list of enabled ciphers in order of cipher priority.
All constants and flags have been converted to IntEnum and
IntFlags.
(Contributed by Christian Heimes in bpo-28025.)
Server and client-side specific TLS protocols for SSLContext
were added.
(Contributed by Christian Heimes in bpo-28085.)
A new harmonic_mean() function has been added.
(Contributed by Steven D’Aprano in bpo-27181.)
struct now supports IEEE 754 half-precision floats via the 'e'
format specifier.
(Contributed by Eli Stevens, Mark Dickinson in bpo-11734.)
subprocess.Popen destructor now emits a ResourceWarning warning
if the child process is still running. Use the context manager protocol (with
proc: ...) or explicitly call the wait() method to
read the exit status of the child process. (Contributed by Victor Stinner in
bpo-26741.)
The subprocess.Popen constructor and all functions that pass arguments
through to it now accept encoding and errors arguments. Specifying either
of these will enable text mode for the stdin, stdout and stderr streams.
(Contributed by Steve Dower in bpo-6135.)
The new getfilesystemencodeerrors() function returns the name of
the error mode used to convert between Unicode filenames and bytes filenames.
(Contributed by Steve Dower in bpo-27781.)
On Windows the return value of the getwindowsversion() function
now includes the platform_version field which contains the accurate major
version, minor version and build number of the current operating system,
rather than the version that is being emulated for the process
(Contributed by Steve Dower in bpo-27932.)
The struct_time attributes tm_gmtoff and
tm_zone are now available on all platforms.
The new Timer.autorange() convenience
method has been added to call Timer.timeit()
repeatedly so that the total run time is greater or equal to 200 milliseconds.
(Contributed by Steven D’Aprano in bpo-6422.)
timeit now warns when there is substantial (4x) variance
between best and worst times.
(Contributed by Serhiy Storchaka in bpo-23552.)
Added methods trace_add(),
trace_remove() and trace_info()
in the tkinter.Variable class. They replace old methods
trace_variable(), trace(),
trace_vdelete() and
trace_vinfo() that use obsolete Tcl commands and might
not work in future versions of Tcl.
(Contributed by Serhiy Storchaka in bpo-22115).
Both the traceback module and the interpreter’s builtin exception display now abbreviate long sequences of repeated lines in tracebacks as shown in the following example:
>>> def f(): f()
...
>>> f()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 1, in f
File "<stdin>", line 1, in f
File "<stdin>", line 1, in f
[Previous line repeated 995 more times]
RecursionError: maximum recursion depth exceeded
(Contributed by Emanuel Barry in bpo-26823.)
The tracemalloc module now supports tracing memory allocations in
multiple different address spaces.
The new DomainFilter filter class has been added
to filter block traces by their address space (domain).
(Contributed by Victor Stinner in bpo-26588.)
Since the typing module is provisional,
all changes introduced in Python 3.6 have also been
backported to Python 3.5.x.
The typing module has a much improved support for generic type
aliases. For example Dict[str, Tuple[S, T]] is now a valid
type annotation.
(Contributed by Guido van Rossum in Github #195.)
The typing.ContextManager class has been added for
representing contextlib.AbstractContextManager.
(Contributed by Brett Cannon in bpo-25609.)
The typing.Collection class has been added for
representing collections.abc.Collection.
(Contributed by Ivan Levkivskyi in bpo-27598.)
The typing.ClassVar type construct has been added to
mark class variables. As introduced in PEP 526, a variable annotation
wrapped in ClassVar indicates that a given attribute is intended to be used as
a class variable and should not be set on instances of that class.
(Contributed by Ivan Levkivskyi in Github #280.)
A new TYPE_CHECKING constant that is assumed to be
True by the static type chekers, but is False at runtime.
(Contributed by Guido van Rossum in Github #230.)
A new NewType() helper function has been added to create
lightweight distinct types for annotations:
from typing import NewType
UserId = NewType('UserId', int)
some_id = UserId(524313)
The static type checker will treat the new type as if it were a subclass of the original type. (Contributed by Ivan Levkivskyi in Github #189.)
The unicodedata module now uses data from Unicode 9.0.0.
(Contributed by Benjamin Peterson.)
The Mock class has the following improvements:
Mock.assert_called() and Mock.assert_called_once() to check if the mock object
was called.
(Contributed by Amit Saha in bpo-26323.)Mock.reset_mock() method
now has two optional keyword only arguments: return_value and
side_effect.
(Contributed by Kushal Das in bpo-21271.)If a HTTP request has a file or iterable body (other than a
bytes object) but no Content-Length header, rather than
throwing an error, AbstractHTTPHandler now
falls back to use chunked transfer encoding.
(Contributed by Demian Brecht and Rolf Krahl in bpo-12319.)
RobotFileParser now supports the Crawl-delay and
Request-rate extensions.
(Contributed by Nikolay Bogoychev in bpo-16099.)
venv accepts a new parameter --prompt. This parameter provides an
alternative prefix for the virtual environment. (Proposed by Łukasz Balcerzak
and ported to 3.6 by Stéphane Wirtel in bpo-22829.)
A new optional source parameter has been added to the
warnings.warn_explicit() function: the destroyed object which emitted a
ResourceWarning. A source attribute has also been added to
warnings.WarningMessage (contributed by Victor Stinner in
bpo-26568 and bpo-26567).
When a ResourceWarning warning is logged, the tracemalloc module is now
used to try to retrieve the traceback where the destroyed object was allocated.
Example with the script example.py:
import warnings
def func():
return open(__file__)
f = func()
f = None
Output of the command python3.6 -Wd -X tracemalloc=5 example.py:
example.py:7: ResourceWarning: unclosed file <_io.TextIOWrapper name='example.py' mode='r' encoding='UTF-8'>
f = None
Object allocated at (most recent call first):
File "example.py", lineno 4
return open(__file__)
File "example.py", lineno 6
f = func()
The “Object allocated at” traceback is new and is only displayed if
tracemalloc is tracing Python memory allocations and if the
warnings module was already imported.
The xmlrpc.client module now supports unmarshalling
additional data types used by the Apache XML-RPC implementation
for numerics and None.
(Contributed by Serhiy Storchaka in bpo-26885.)
A new ZipInfo.from_file() class method
allows making a ZipInfo instance from a filesystem file.
A new ZipInfo.is_dir() method can be used
to check if the ZipInfo instance represents a directory.
(Contributed by Thomas Kluyver in bpo-26039.)
The ZipFile.open() method can now be used to
write data into a ZIP file, as well as for extracting data.
(Contributed by Thomas Kluyver in bpo-26039.)
The compress() and decompress() functions now accept
keyword arguments.
(Contributed by Aviv Palivoda in bpo-26243 and
Xiang Zhang in bpo-16764 respectively.)
asyncio.Future class now has an optimized C implementation.
(Contributed by Yury Selivanov and INADA Naoki in bpo-26081.)asyncio.Task class now has an optimized
C implementation. (Contributed by Yury Selivanov in bpo-28544.)typing module
(such as caching of generic types) allow up to 30 times performance
improvements and reduced memory footprint.surrogateescape, ignore and replace (Contributed
by Victor Stinner in bpo-24870).surrogateescape
(Contributed by Victor Stinner in bpo-25227).ignore, replace, surrogateescape, surrogatepass (Contributed
by Victor Stinner in bpo-25267).ignore, replace and surrogateescape (Contributed
by Victor Stinner in bpo-25301).bytes % args is now up to 2 times faster. (Contributed by Victor Stinner
in bpo-25349).bytearray % args is now between 2.5 and 5 times faster. (Contributed by
Victor Stinner in bpo-25399).bytes.fromhex() and bytearray.fromhex(): they are now
between 2x and 3.5x faster. (Contributed by Victor Stinner in bpo-25401).bytes.replace(b'', b'.') and bytearray.replace(b'', b'.'):
up to 80% faster. (Contributed by Josh Snider in bpo-26574).PyMem_Malloc() domain
(PYMEM_DOMAIN_MEM) now use the pymalloc memory allocator instead of malloc() function of the C library. The
pymalloc allocator is optimized for objects smaller or equal to 512 bytes
with a short lifetime, and use malloc() for larger memory blocks.
(Contributed by Victor Stinner in bpo-26249).pickle.load() and pickle.loads() are now up to 10% faster when
deserializing many small objects (Contributed by Victor Stinner in
bpo-27056).glob() and iglob() functions in the
glob module; they are now about 3–6 times faster.
(Contributed by Serhiy Storchaka in bpo-25596).pathlib by using os.scandir();
it is now about 1.5–4 times faster.
(Contributed by Serhiy Storchaka in bpo-26032).xml.etree.ElementTree parsing, iteration and deepcopy performance
has been significantly improved.
(Contributed by Serhiy Storchaka in bpo-25638, bpo-25873,
and bpo-25869.)fractions.Fraction instances from floats and
decimals is now 2 to 3 times faster.
(Contributed by Serhiy Storchaka in bpo-25971.)PY_LONG_LONG.
For more information, see PEP 7 and bpo-17884.--enable-optimizations configure flag has been added. Turning it on
will activate expensive optimizations like PGO.
(Original patch by Alecsandru Patrascu of Intel in bpo-26359.)PYMEM_DOMAIN_OBJ (ex: PyObject_Malloc()) and
PYMEM_DOMAIN_MEM (ex: PyMem_Malloc()) domains are called.Py_FinalizeEx() API which indicates if flushing buffered data
failed.
(Contributed by Martin Panter in bpo-5319.)PyArg_ParseTupleAndKeywords() now supports positional-only
parameters. Positional-only parameters are
defined by empty names.
(Contributed by Serhiy Storchaka in bpo-26282).PyTraceback_Print method now abbreviates long sequences of repeated lines
as "[Previous line repeated {count} more times]".
(Contributed by Emanuel Barry in bpo-26823.)PyErr_SetImportErrorSubclass() function allows for
specifying a subclass of ImportError to raise.
(Contributed by Eric Snow in bpo-15767.)PyErr_ResourceWarning() function can be used to generate
a ResourceWarning providing the source of the resource allocation.
(Contributed by Victor Stinner in bpo-26567.)PyOS_FSPath() function returns the file system
representation of a path-like object.
(Contributed by Brett Cannon in bpo-27186.)PyUnicode_FSConverter() and PyUnicode_FSDecoder()
functions will now accept path-like objects.When --version (short form: -V) is supplied twice,
Python prints sys.version for detailed information.
$ ./python -VV
Python 3.6.0b4+ (3.6:223967b49e49+, Nov 21 2016, 20:55:04)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)]
async and await are not recommended to be used as variable, class,
function or module names. Introduced by PEP 492 in Python 3.5, they will
become proper keywords in Python 3.7. Starting in Python 3.6, the use of
async or await as names will generate a DeprecationWarning.
Raising the StopIteration exception inside a generator will now
generate a DeprecationWarning, and will trigger a RuntimeError
in Python 3.7. See PEP 479: Change StopIteration handling inside generators for details.
The __aiter__() method is now expected to return an asynchronous
iterator directly instead of returning an awaitable as previously.
Doing the former will trigger a DeprecationWarning. Backward
compatibility will be removed in Python 3.7.
(Contributed by Yury Selivanov in bpo-27243.)
A backslash-character pair that is not a valid escape sequence now generates
a DeprecationWarning. Although this will eventually become a
SyntaxError, that will not be for several Python releases.
(Contributed by Emanuel Barry in bpo-27364.)
When performing a relative import, falling back on __name__ and
__path__ from the calling module when __spec__ or
__package__ are not defined now raises an ImportWarning.
(Contributed by Rose Ames in bpo-25791.)
The asynchat has been deprecated in favor of asyncio.
(Contributed by Mariatta in bpo-25002.)
The asyncore has been deprecated in favor of asyncio.
(Contributed by Mariatta in bpo-25002.)
Unlike other dbm implementations, the dbm.dumb module
creates databases with the 'rw' mode and allows modifying the database
opened with the 'r' mode. This behavior is now deprecated and will
be removed in 3.8.
(Contributed by Serhiy Storchaka in bpo-21708.)
The undocumented extra_path argument to the
Distribution constructor is now considered deprecated
and will raise a warning if set. Support for this parameter will be
removed in a future Python release. See bpo-27919 for details.
The support of non-integer arguments in getgrgid() has been
deprecated.
(Contributed by Serhiy Storchaka in bpo-26129.)
The importlib.machinery.SourceFileLoader.load_module() and
importlib.machinery.SourcelessFileLoader.load_module() methods
are now deprecated. They were the only remaining implementations of
importlib.abc.Loader.load_module() in importlib that had not
been deprecated in previous versions of Python in favour of
importlib.abc.Loader.exec_module().
The importlib.machinery.WindowsRegistryFinder class is now
deprecated. As of 3.6.0, it is still added to sys.meta_path by
default (on Windows), but this may change in future releases.
Undocumented support of general bytes-like objects
as paths in os functions, compile() and similar functions is
now deprecated.
(Contributed by Serhiy Storchaka in bpo-25791 and bpo-26754.)
Support for inline flags (?letters) in the middle of the regular
expression has been deprecated and will be removed in a future Python
version. Flags at the start of a regular expression are still allowed.
(Contributed by Serhiy Storchaka in bpo-22493.)
OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported.
In the future the ssl module will require at least OpenSSL 1.0.2 or
1.1.0.
SSL-related arguments like certfile, keyfile and check_hostname
in ftplib, http.client, imaplib, poplib,
and smtplib have been deprecated in favor of context.
(Contributed by Christian Heimes in bpo-28022.)
A couple of protocols and functions of the ssl module are now
deprecated. Some features will no longer be available in future versions
of OpenSSL. Other features are deprecated in favor of a different API.
(Contributed by Christian Heimes in bpo-28022 and bpo-26470.)
The tkinter.tix module is now deprecated. tkinter users
should use tkinter.ttk instead.
Undocumented functions PyUnicode_AsEncodedObject(),
PyUnicode_AsDecodedObject(), PyUnicode_AsEncodedUnicode()
and PyUnicode_AsDecodedUnicode() are deprecated now.
Use the generic codec based API instead.
The --with-system-ffi configure flag is now on by default on non-macOS
UNIX platforms. It may be disabled by using --without-system-ffi, but
using the flag is deprecated and will not be accepted in Python 3.7.
macOS is unaffected by this change. Note that many OS distributors already
use the --with-system-ffi flag when building their system Python.
'\' and an ASCII letter in
regular expressions will now cause an error. In replacement templates for
re.sub() they are still allowed, but deprecated.
The re.LOCALE flag can now only be used with binary patterns.inspect.getmoduleinfo() was removed (was deprecated since CPython 3.3).
inspect.getmodulename() should be used for obtaining the module
name for a given path.
(Contributed by Yury Selivanov in bpo-13248.)traceback.Ignore class and traceback.usage, traceback.modname,
traceback.fullmodname, traceback.find_lines_from_code,
traceback.find_lines, traceback.find_strings,
traceback.find_executable_lines methods were removed from the
traceback module. They were undocumented methods deprecated since
Python 3.2 and equivalent functionality is available from private methods.tk_menuBar() and tk_bindForTraversal() dummy methods in
tkinter widget classes were removed (corresponding Tk commands
were obsolete since Tk 4.0).open() method of the zipfile.ZipFile
class no longer supports the 'U' mode (was deprecated since Python 3.4).
Use io.TextIOWrapper for reading compressed text files in
universal newlines mode.IN, CDROM, DLFCN, TYPES, CDIO, and
STROPTS modules have been removed. They had been available in the
platform specific Lib/plat-*/ directories, but were chronically out of
date, inconsistently available across platforms, and unmaintained. The
script that created these modules is still available in the source
distribution at Tools/scripts/h2py.py.asynchat.fifo class has been removed.This section lists previously described changes and other bugfixes that may require changes to your code.
COUNT_ALLOCS,
SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by
default. It can be re-enabled using the -X showalloccount option.
It now outputs to stderr instead of stdout.
(Contributed by Serhiy Storchaka in bpo-23034.)open() will no longer allow combining the 'U' mode flag
with '+'.
(Contributed by Jeff Balogh and John O’Connor in bpo-2091.)
sqlite3 no longer implicitly commits an open transaction before DDL
statements.
On Linux, os.urandom() now blocks until the system urandom entropy pool
is initialized to increase the security.
When importlib.abc.Loader.exec_module() is defined,
importlib.abc.Loader.create_module() must also be defined.
PyErr_SetImportError() now sets TypeError when its msg
argument is not set. Previously only NULL was returned.
The format of the co_lnotab attribute of code objects changed to support
a negative line number delta. By default, Python does not emit bytecode with
a negative line number delta. Functions using frame.f_lineno,
PyFrame_GetLineNumber() or PyCode_Addr2Line() are not affected.
Functions directly decoding co_lnotab should be updated to use a signed
8-bit integer type for the line number delta, but this is only required to
support applications using a negative line number delta. See
Objects/lnotab_notes.txt for the co_lnotab format and how to decode
it, and see the PEP 511 for the rationale.
The functions in the compileall module now return booleans instead
of 1 or 0 to represent success or failure, respectively. Thanks to
booleans being a subclass of integers, this should only be an issue if you
were doing identity checks for 1 or 0. See bpo-25768.
Reading the port attribute of
urllib.parse.urlsplit() and urlparse() results
now raises ValueError for out-of-range values, rather than
returning None. See bpo-20059.
The imp module now raises a DeprecationWarning instead of
PendingDeprecationWarning.
The following modules have had missing APIs added to their __all__
attributes to match the documented APIs:
calendar, cgi, csv,
ElementTree, enum,
fileinput, ftplib, logging, mailbox,
mimetypes, optparse, plistlib, smtpd,
subprocess, tarfile, threading and
wave. This means they will export new symbols when import *
is used.
(Contributed by Joel Taddei and Jacek Kołodziej in bpo-23883.)
When performing a relative import, if __package__ does not compare equal
to __spec__.parent then ImportWarning is raised.
(Contributed by Brett Cannon in bpo-25791.)
When a relative import is performed and no parent package is known, then
ImportError will be raised. Previously, SystemError could be
raised. (Contributed by Brett Cannon in bpo-18018.)
Servers based on the socketserver module, including those
defined in http.server, xmlrpc.server and
wsgiref.simple_server, now only catch exceptions derived
from Exception. Therefore if a request handler raises
an exception like SystemExit or KeyboardInterrupt,
handle_error() is no longer called, and
the exception will stop a single-threaded server. (Contributed by
Martin Panter in bpo-23430.)
spwd.getspnam() now raises a PermissionError instead of
KeyError if the user doesn’t have privileges.
The socket.socket.close() method now raises an exception if
an error (e.g. EBADF) was reported by the underlying system call.
(Contributed by Martin Panter in bpo-26685.)
The decode_data argument for the smtpd.SMTPChannel and
smtpd.SMTPServer constructors is now False by default.
This means that the argument passed to
process_message() is now a bytes object by
default, and process_message() will be passed keyword arguments.
Code that has already been updated in accordance with the deprecation
warning generated by 3.5 will not be affected.
All optional arguments of the dump(), dumps(),
load() and loads() functions and
JSONEncoder and JSONDecoder class
constructors in the json module are now keyword-only.
(Contributed by Serhiy Storchaka in bpo-18726.)
Subclasses of type which don’t override type.__new__ may no
longer use the one-argument form to get the type of an object.
As part of PEP 487, the handling of keyword arguments passed to
type (other than the metaclass hint, metaclass) is now
consistently delegated to object.__init_subclass__(). This means that
type.__new__() and type.__init__() both now accept arbitrary
keyword arguments, but object.__init_subclass__() (which is called from
type.__new__()) will reject them by default. Custom metaclasses
accepting additional keyword arguments will need to adjust their calls to
type.__new__() (whether direct or via super) accordingly.
In distutils.command.sdist.sdist, the default_format
attribute has been removed and is no longer honored. Instead, the
gzipped tarfile format is the default on all platforms and no
platform-specific selection is made.
In environments where distributions are
built on Windows and zip distributions are required, configure
the project with a setup.cfg file containing the following:
[sdist]
formats=zip
This behavior has also been backported to earlier Python versions by Setuptools 26.0.0.
In the urllib.request module and the
http.client.HTTPConnection.request() method, if no Content-Length
header field has been specified and the request body is a file object,
it is now sent with HTTP 1.1 chunked encoding. If a file object has to
be sent to a HTTP 1.0 server, the Content-Length value now has to be
specified by the caller.
(Contributed by Demian Brecht and Rolf Krahl with tweaks from
Martin Panter in bpo-12319.)
The DictReader now returns rows of type
OrderedDict.
(Contributed by Steve Holden in bpo-27842.)
The crypt.METHOD_CRYPT will no longer be added to crypt.methods
if unsupported by the platform.
(Contributed by Victor Stinner in bpo-25287.)
The verbose and rename arguments for
namedtuple() are now keyword-only.
(Contributed by Raymond Hettinger in bpo-25628.)
On Linux, ctypes.util.find_library() now looks in
LD_LIBRARY_PATH for shared libraries.
(Contributed by Vinay Sajip in bpo-9998.)
The imaplib.IMAP4 class now handles flags containing the
']' character in messages sent from the server to improve
real-world compatibility.
(Contributed by Lita Cho in bpo-21815.)
The mmap.write() function now returns the number
of bytes written like other write methods.
(Contributed by Jakub Stasiak in bpo-26335.)
The pkgutil.iter_modules() and pkgutil.walk_packages()
functions now return ModuleInfo named tuples.
(Contributed by Ramchandra Apte in bpo-17211.)
re.sub() now raises an error for invalid numerical group
references in replacement templates even if the pattern is not
found in the string. The error message for invalid group references
now includes the group index and the position of the reference.
(Contributed by SilentGhost, Serhiy Storchaka in bpo-25953.)
zipfile.ZipFile will now raise NotImplementedError for
unrecognized compression values. Previously a plain RuntimeError
was raised. Additionally, calling ZipFile methods
on a closed ZipFile or calling the write() method
on a ZipFile created with mode 'r' will raise a ValueError.
Previously, a RuntimeError was raised in those scenarios.
when custom metaclasses are combined with zero-argument super() or
direct references from methods to the implicit __class__ closure
variable, the implicit __classcell__ namespace entry must now be passed
up to type.__new__ for initialisation. Failing to do so will result in
a DeprecationWarning in 3.6 and a RuntimeWarning in the future.
PyMem_Malloc() allocator family now uses the pymalloc allocator rather than the system malloc(). Applications calling
PyMem_Malloc() without holding the GIL can now crash. Set the
PYTHONMALLOC environment variable to debug to validate the
usage of memory allocators in your application. See bpo-26249.Py_Exit() (and the main interpreter) now override the exit status
with 120 if flushing buffered data failed. See bpo-5319.There have been several major changes to the bytecode in Python 3.6.
FORMAT_VALUE and BUILD_STRING opcodes as part
of the formatted string literal implementation.
(Contributed by Eric Smith in bpo-25483 and
Serhiy Storchaka in bpo-27078.)BUILD_CONST_KEY_MAP opcode to optimize the creation
of dictionaries with constant keys.
(Contributed by Serhiy Storchaka in bpo-27140.)MAKE_FUNCTION, CALL_FUNCTION,
CALL_FUNCTION_KW and BUILD_MAP_UNPACK_WITH_CALL opcodes
have been modified, the new CALL_FUNCTION_EX and
BUILD_TUPLE_UNPACK_WITH_CALL have been added, and
CALL_FUNCTION_VAR, CALL_FUNCTION_VAR_KW and MAKE_CLOSURE opcodes
have been removed.
(Contributed by Demur Rumed in bpo-27095, and Serhiy Storchaka in
bpo-27213, bpo-28257.)SETUP_ANNOTATIONS and STORE_ANNOTATION opcodes
have been added to support the new variable annotation syntax.
(Contributed by Ivan Levkivskyi in bpo-27985.)