Editors:Elvis Pranskevichus <
>, Yury Selivanov <
>
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
for a full list of changes.
See also
- Python 3.6 Release Schedule
Summary – Release highlights
New syntax features:
, formatted string literals.
, underscores in numeric literals.
, syntax for variable annotations.
, asynchronous generators.
: asynchronous comprehensions.
New library modules:
:
PEP 506 – Adding A Secrets Module To The Standard Library
.
CPython implementation improvements:
The
type has been reimplemented to use a
based on
a proposal by Raymond Hettinger
and similar to the
. This resulted in dictionaries using 20% to 25% less memory when compared to Python 3.5.
Customization of class creation has been simplified with the
.
The class attribute definition order is
.
The order of elements in **kwargs now
in which keyword arguments were passed to the function.
DTrace and SystemTap
has been added.
The new
environment variable can now be used to debug the interpreter memory allocation and access errors.
Significant improvements in the standard library:
The
module has received new features, significant usability and performance improvements, and a fair amount of bug fixes. Starting with Python 3.6 the asyncio module is no longer provisional and its API is considered stable.
A new
has been implemented to support
. All standard library functions operating on paths have been updated to work with the new protocol.
The
module has gained support for
.
The
module received a number of
.
The
module has been significantly reworked and is now used to provide better output for
as well as provide better diagnostics for memory allocation errors. See the
for more information.
Security improvements:
The new
module has been added to simplify the generation of cryptographically strong pseudo-random numbers suitable for managing secrets such as account authentication, tokens, and similar.
On Linux,
now blocks until the system urandom entropy pool is initialized to increase the security. See the
for the rationale.
The
and
modules now support OpenSSL 1.1.0.
The default settings and feature set of the
module have been improved.
The
module received support for the BLAKE2, SHA-3 and SHAKE hash algorithms and the
key derivation function.
Windows improvements:
and
, Windows filesystem and console encoding changed to UTF-8.
The py.exe launcher, when used interactively, no longer prefers Python 2 over Python 3 when the user doesn’t specify a version (via command line arguments or a config file). Handling of shebang lines remains unchanged - “python” refers to Python 2 in that case.
python.exe and pythonw.exe have been marked as long-path aware, which means that the 260 character path limit may no longer apply. See
removing the MAX_PATH limitation
for details.
A ._pth file can be added to force isolated mode and fully specify all search paths to avoid registry and environment lookup. See
for more information.
A python36.zip file now works as a landmark to infer
. See
for more information.
New Features
PEP 498: Formatted string literals
introduces a new kind of string literals: f-strings, or
.
Formatted string literals are prefixed with 'f' and are similar to the format strings accepted by
. They contain replacement fields surrounded by curly braces. The replacement fields are expressions, which are evaluated at run time, and then formatted using the
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'PEP 526: Syntax for variable annotations
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!classStarship: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.
See also
– Syntax for variable annotations.PEP written by Ryan Gonzalez, Philip House, Ivan Levkivskyi, Lisa Roach, and Guido van Rossum. Implemented by Ivan Levkivskyi.
Tools that use or will use the new syntax:
,
, PyCharm, etc.
PEP 515: Underscores in Numeric Literals
adds the ability to use underscores in numeric literals for improved readability. For example:
>>> 1_000_000_000_000_0001000000000000000>>> 0x_FF_FF_FF_FF4294967295Single underscores are allowed between digits and after any base specifier. Leading, trailing, or multiple underscores in a row are not allowed.
The
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
– Underscores in Numeric LiteralsPEP written by Georg Brandl and Serhiy Storchaka.
PEP 525: Asynchronous Generators
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:
asyncdefticker(delay,to):"""Yield numbers from 0 to *to* every *delay* seconds."""foriinrange(to):yieldiawaitasyncio.sleep(delay)The new syntax allows for faster and more concise code.
See also
– Asynchronous GeneratorsPEP written and implemented by Yury Selivanov.
PEP 530: Asynchronous Comprehensions
adds support for using asyncfor in list, set, dict comprehensions and generator expressions:
result=[iasyncforiinaiter()ifi%2]Additionally, await expressions are supported in all kinds of comprehensions:
result=[awaitfun()forfuninfuncsifawaitcondition()]See also
– Asynchronous ComprehensionsPEP written and implemented by Yury Selivanov.
PEP 487: Simpler customization of class creation
It is now possible to customize subclass creation without using a metaclass. The new __init_subclass__ classmethod will be called on the base class whenever a new subclass is created:
classPluginBase:subclasses=[]def__init_subclass__(cls,**kwargs):super().__init_subclass__(**kwargs)cls.subclasses.append(cls)classPlugin1(PluginBase):passclassPlugin2(PluginBase):passIn order to allow zero-argument
calls to work correctly from
implementations, custom metaclasses must ensure that the new __classcell__ namespace entry is propagated to type.__new__ (as described in
).
PEP 487: Descriptor Protocol Enhancements
extends the descriptor protocol to include the new optional
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:
classIntField:def__get__(self,instance,owner):returninstance.__dict__[self.name]def__set__(self,instance,value):ifnotisinstance(value,int):raiseValueError(f'expecting integer in {self.name}')instance.__dict__[self.name]=value# this is the new initializer:def__set_name__(self,owner,name):self.name=nameclassModel:int_field=IntField()PEP 519: Adding a file system path protocol
File system paths have historically been represented as
or
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
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
from working with pre-existing code, including Python’s standard library.
To fix this situation, a new interface represented by
has been defined. By implementing the
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
or
object. This means an object is considered
if it implements os.PathLike or is a str or bytes object which represents a file system path. Code can use
,
, or
to explicitly get a str and/or bytes representation of a path-like object.
The built-in
function has been updated to accept
objects, as have all relevant functions in the
and
modules, and most other functions and classes in the standard library. The
class and relevant classes in
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
without any code changes, or at least very minimal ones (e.g. calling
at the beginning of code before operating on a path-like object).
Here are some examples of how the new interface allows for
to be used more easily and transparently with pre-existing code:
>>> importpathlib>>> withopen(pathlib.Path("README"))asf:... contents=f.read()...>>> importos.path>>> os.path.splitext(pathlib.Path("some_file.txt"))('some_file', '.txt')>>> os.path.join("/a/b",pathlib.Path("c"))'/a/b/c'>>> importos>>> os.fspath(pathlib.Path("some_file.txt"))'some_file.txt'(Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.)
See also
– Adding a file system path protocolPEP written by Brett Cannon and Koos Zevenhoven.
PEP 495: Local Time Disambiguation
In most world locations, there have been and will be times when local clocks are moved back. In those times, intervals are introduced in which local clocks show the same time twice in the same day. In these situations, the information displayed on a local clock (or stored in a Python datetime instance) is insufficient to identify a particular moment in time.
adds the new fold attribute to instances of
and
classes to differentiate between two moments in time for which local times are the same:
>>> u0=datetime(2016,11,6,4,tzinfo=timezone.utc)>>> foriinrange(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 005:00:00 UTC = 01:00:00 EDT 006:00:00 UTC = 01:00:00 EST 107:00:00 UTC = 02:00:00 EST 0The values of the
attribute have the value 0 for all instances except those that represent the second (chronologically) moment in time in an ambiguous case.
See also
– Local Time DisambiguationPEP written by Alexander Belopolsky and Tim Peters, implementation by Alexander Belopolsky.
PEP 529: Change Windows filesystem encoding to UTF-8
Representing filesystem paths is best performed with str (Unicode) rather than bytes. However, there are some situations where using bytes is sufficient and correct.
Prior to Python 3.6, data loss could result when using bytes paths on Windows. With this change, using bytes to represent paths is now supported on Windows, provided those bytes are encoded with the encoding returned by
, which now defaults to 'utf-8'.
Applications that do not use str to represent paths should use
and
to ensure their bytes are correctly encoded. To revert to the previous behaviour, set
or call sys._enablelegacywindowsfsencoding().
See
for more information and discussion of code modifications that may be required.
PEP 528: Change Windows console encoding to UTF-8
The default console on Windows will now accept all Unicode characters and provide correctly read str objects to Python code. sys.stdin, sys.stdout and sys.stderr now default to utf-8 encoding.
This change only applies when using an interactive console, and not when redirecting files or pipes. To revert to the previous behaviour for interactive console use, set
.
See also
– Change Windows console encoding to UTF-8PEP written and implemented by Steve Dower.
PEP 520: Preserving Class Attribute Definition Order
Attributes in a class definition body have a natural ordering: the same order in which the names appear in the source. This order is now preserved in the new class’s
attribute.
Also, the effective default class execution namespace (returned from
) is now an insertion-order-preserving mapping.
See also
– Preserving Class Attribute Definition OrderPEP written and implemented by Eric Snow.
PEP 468: Preserving Keyword Argument Order
**kwargs in a function signature is now guaranteed to be an insertion-order-preserving mapping.
See also
– Preserving Keyword Argument OrderPEP written and implemented by Eric Snow.
New
implementation
The
type now uses a “compact” representation based on
a proposal by Raymond Hettinger
which was
. The memory usage of the new
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
. Idea
originally suggested by Raymond Hettinger
.)
PEP 523: Adding a frame evaluation API to CPython
While Python provides extensive support to customize how code executes, one place it has not done so is in the evaluation of frame objects. If you wanted some way to intercept frame evaluation in Python there really wasn’t any way without directly manipulating function pointers for defined functions.
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
– Adding a frame evaluation API to CPythonPEP written by Brett Cannon and Dino Viehland.
PYTHONMALLOC environment variable
The new
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:
Newly allocated memory is filled with the byte 0xCB
Freed memory is filled with the byte 0xDB
Detect violations of the Python memory allocator API. For example,
called on a memory block allocated by
.
Detect writes before the start of a buffer (buffer underflows)
Detect writes after the end of a buffer (buffer overflows)
Check that the
is held when allocator functions of
(ex:
) and
(ex:
) domains are called.
Checking if the GIL is held is also a new feature of Python 3.6.
See the
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
module to get the traceback where a memory block was allocated.
Example of fatal error on buffer overflow using python3.6-Xtracemalloc=5 (store 5 frames in traces):
Debugmemoryblockataddressp=0x7fbcd41666f8:API'o'4bytesoriginallyrequestedThe7padbytesatp-7areFORBIDDENBYTE,asexpected.The8padbytesattail=0x7fbcd41666fcarenotallFORBIDDENBYTE(0xfb):attail+0:0x02***OUCHattail+1:0xfbattail+2:0xfbattail+3:0xfbattail+4:0xfbattail+5:0xfbattail+6:0xfbattail+7:0xfbTheblockwasmadebycall#1233329 to debug malloc/realloc.Dataatp:1a2b3000Memoryblockallocatedat(mostrecentcallfirst):File"test/test_bytes.py",line323File"unittest/case.py",line600File"unittest/case.py",line648File"unittest/suite.py",line122File"unittest/suite.py",line84FatalPythonerror:badtrailingpadbyteCurrentthread0x00007fbcdbd32700(mostrecentcallfirst):File"test/test_bytes.py",line323intest_hexFile"unittest/case.py",line600inrunFile"unittest/case.py",line648in__call__File"unittest/suite.py",line122inrunFile"unittest/suite.py",line84in__call__File"unittest/suite.py",line122inrunFile"unittest/suite.py",line84in__call__...(Contributed by Victor Stinner in
and
.)
DTrace and SystemTap probing support
Python can now be built --with-dtrace which enables static markers for the following events in the interpreter:
function call/return
garbage collection started/finished
line of code executed.
This can be used to instrument running interpreters in production, without the need to recompile specific
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
, based on patches by Jesús Cea Avión, David Malcolm, and Nikhil Benesch.)
Other Language Changes
Some smaller changes made to the core Python language are:
A global or nonlocal statement must now textually appear before the first use of the affected name in the same scope. Previously this was a
.
It is now possible to set a
to None to indicate that the corresponding operation is not available. For example, if a class sets
to None, the class is not iterable. (Contributed by Andrew Barnert and Ivan Levkivskyi in
.)
Long sequences of repeated traceback lines are now abbreviated as "[Previouslinerepeated{count}moretimes]" (see
for an example). (Contributed by Emanuel Barry in
.)
Import now raises the new exception
(subclass of
) when it cannot find a module. Code that currently checks for ImportError (in try-except) will still work. (Contributed by Eric Snow in
.)
Class methods relying on zero-argument super() will now work correctly when called from metaclass methods during class creation. (Contributed by Martin Teichmann in
.)
New Modules
secrets
The main purpose of the new
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
module should NOT be used for security purposes. Use
on Python 3.6+ and
on Python 3.5 and earlier.
See also
– Adding A Secrets Module To The Standard LibraryPEP written and implemented by Steven D’Aprano.
Improved Modules
array
Exhausted iterators of
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
.
ast
The new
AST node has been added. It can be used by external AST optimizers for the purposes of constant folding.
Contributed by Victor Stinner in
.
asyncio
Starting with Python 3.6 the asyncio module is no longer provisional and its API is considered stable.
Notable changes in the
module since Python 3.5.0 (all backported to 3.5.x due to the provisional status):
The
function has been changed to always return the currently running loop when called from coroutines and callbacks. (Contributed by Yury Selivanov in
.)
The
function and all functions that use it, such as
, now accept all kinds of
. (Contributed by Yury Selivanov.)
New
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
method can now accept a list of hosts. (Contributed by Yann Sionneau.)
New
method to create Future objects. This allows alternative event loop implementations, such as
, to provide a faster
implementation. (Contributed by Yury Selivanov in
.)
New
method to get the current exception handler. (Contributed by Yury Selivanov in
.)
New
method to read data from the stream until a separator bytes sequence appears. (Contributed by Mark Korenberg.)
The performance of
has been improved. (Contributed by Mark Korenberg in
.)
The
method is optimized to avoid calling the system getaddrinfo function if the address is already resolved. (Contributed by A. Jesse Jiryu Davis.)
The
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
.)
will now raise
when passed an instance of the
exception. (Contributed by Chris Angelico in
.)
New
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
.)
TCP_NODELAY flag is now set for all TCP transports by default. (Contributed by Yury Selivanov in
.)
New
to properly close pending asynchronous generators before closing the loop. (Contributed by Yury Selivanov in
.)
and
classes now have an optimized C implementation which makes asyncio code up to 30% faster. (Contributed by Yury Selivanov and INADA Naoki in
and
.)
binascii
The
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
.)
cmath
The new
(τ) constant has been added. (Contributed by Lisa Roach in
, see
for details.)
New constants:
and
to match
and
, and also
and
to match the format used by complex repr. (Contributed by Mark Dickinson in
.)
collections
The new
abstract base class has been added to represent sized iterable container classes. (Contributed by Ivan Levkivskyi, docs by Neil Girdhar in
.)
The new
abstract base class represents iterable classes that also provide the
method. (Contributed by Ivan Levkivskyi in
.)
The new
abstract base class represents asynchronous generators. (Contributed by Yury Selivanov in
.)
The
function now accepts an optional keyword argument module, which, when specified, is used for the
attribute of the returned named tuple class. (Contributed by Raymond Hettinger in
.)
The verbose and rename arguments for
are now keyword-only. (Contributed by Raymond Hettinger in
.)
Recursive
instances can now be pickled. (Contributed by Serhiy Storchaka in
.)
concurrent.futures
The
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
.)
contextlib
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
module as
. (Contributed by Brett Cannon in
.)
datetime
The
and
classes have the new
attribute used to disambiguate local time when necessary. Many functions in the
have been updated to support local time disambiguation. See
section for more information. (Contributed by Alexander Belopolsky in
.)
The
and
methods now support ISO 8601 date directives %G, %u and %V. (Contributed by Ashley Anderson in
.)
The
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
.)
The
now accepts an optional tzinfo argument. (Contributed by Alexander Belopolsky in
.)
decimal
New
method that returns a pair (n,d) of integers that represent the given
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
.)
distutils
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
for more details.
The new email API, enabled via the policy keyword to various constructors, is no longer provisional. The
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
.)
The
classes now all accept an optional policy keyword. (Contributed by Berker Peksag in
.)
The
now supports the policy keyword.
There is a new
attribute,
, that controls what class is used by default when the parser creates new message objects. For the
policy this is
, for the new policies it is
. (Contributed by R. David Murray in
.)
encodings
On Windows, added the 'oem' encoding to use CP_OEMCP, and the 'ansi' alias for the existing 'mbcs' encoding, which uses the CP_ACP code page. (Contributed by Steve Dower in
.)
enum
Two new enumeration base classes have been added to the
module:
and
. Both are used to define constants that can be combined using the bitwise operators. (Contributed by Ethan Furman in
.)
Many standard library modules have been updated to use the
class for their constants.
The new
value can be used to assign values to enum members automatically:
>>> fromenumimportEnum,auto>>> classColor(Enum):... red=auto()... blue=auto()... green=auto()...>>> list(Color)[<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>]faulthandler
On Windows, the
module now installs a handler for Windows exceptions: see
. (Contributed by Victor Stinner in
.)
fileinput
now supports the errors argument. (Contributed by Joseph Hackman in
.)
hashlib
supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in
.)
BLAKE2 hash functions were added to the module.
and
are always available and support the full feature set of BLAKE2. (Contributed by Christian Heimes in
based on code by Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.)
The SHA-3 hash functions
,
,
,
, and SHAKE hash functions
and
were added. (Contributed by Christian Heimes in
. Keccak Code Package by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and Ronny Van Keer.)
The password-based key derivation function
is now available with OpenSSL 1.1.0 and newer. (Contributed by Christian Heimes in
.)
http.client
and
both now support chunked encoding request bodies. (Contributed by Demian Brecht and Rolf Krahl in
.)
idlelib and IDLE
The idlelib package is being modernized and refactored to make IDLE look and work better and to make the code easier to understand, test, and improve. Part of making IDLE look better, especially on Linux and Mac, is using ttk widgets, mostly in the dialogs. As a result, IDLE no longer runs with tcl/tk 8.4. It now requires tcl/tk 8.5 or 8.6. We recommend running the latest release of either.
‘Modernizing’ includes renaming and consolidation of idlelib modules. The renaming of files with partial uppercase names is similar to the renaming of, for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0. As a result, imports of idlelib files that worked in 3.5 will usually not work in 3.6. At least a module name change will be needed (see idlelib/README.txt), sometimes more. (Name changes contributed by Al Swiegart and Terry Reedy in
. 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.
New in 3.6.2:
Multiple fixes for autocompletion. (Contributed by Louie Lu in
.)
New in 3.6.3:
Module Browser (on the File menu, formerly called Class Browser), now displays nested functions and classes in addition to top-level functions and classes. (Contributed by Guilherme Polo, Cheryl Sabella, and Terry Jan Reedy in
.)
The IDLE features formerly implemented as extensions have been reimplemented as normal features. Their settings have been moved from the Extensions tab to other dialog tabs. (Contributed by Charles Wohlganger and Terry Jan Reedy in
.)
The Settings dialog (Options, Configure IDLE) has been partly rewritten to improve both appearance and function. (Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues.)
New in 3.6.4:
The font sample now includes a selection of non-Latin characters so that users can better see the effect of selecting a particular font. (Contributed by Terry Jan Reedy in
.) The sample can be edited to include other characters. (Contributed by Serhiy Storchaka in
.)
New in 3.6.6:
Editor code context option revised. Box displays all context lines up to maxlines. Clicking on a context line jumps the editor to that line. Context colors for custom themes is added to Highlights tab of Settings dialog. (Contributed by Cheryl Sabella and Terry Jan Reedy in
,
, and
.)
On Windows, a new API call tells Windows that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect. (Contributed by Terry Jan Reedy in
.)
New in 3.6.7:
Output over N lines (50 by default) is squeezed down to a button. N can be changed in the PyShell section of the General page of the Settings dialog. Fewer, but possibly extra long, lines can be squeezed by right clicking on the output. Squeezed output can be expanded in place by double-clicking the button or into the clipboard or a separate window by right-clicking the button. (Contributed by Tal Einat in
.)
importlib
Import now raises the new exception
(subclass of
) when it cannot find a module. Code that current checks for ImportError (in try-except) will still work. (Contributed by Eric Snow in
.)
now calls
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
.
inspect
The
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
.)
To reduce code churn when upgrading from Python 2.7 and the legacy inspect.getargspec() API, the previously documented deprecation of
has been reversed. While this function is convenient for single/source Python 2/3 code bases, the richer
interface remains the recommended approach for new code. (Contributed by Nick Coghlan in
)
json
and
now support binary input. Encoded JSON should be represented using either UTF-8, UTF-16, or UTF-32. (Contributed by Serhiy Storchaka in
.)
logging
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
.)
math
The tau (τ) constant has been added to the
and
modules. (Contributed by Lisa Roach in
, see
for details.)
multiprocessing
returned by
can now be nested. (Contributed by Davin Potts in
.)
os
See the summary of
for details on how the
and
modules now support
.
now supports
paths on Windows.
A new
method allows explicitly closing a
iterator. The scandir() iterator now supports the
protocol. If a scandir() iterator is neither exhausted nor explicitly closed a
will be emitted in its destructor. (Contributed by Serhiy Storchaka in
.)
On Linux,
now blocks until the system urandom entropy pool is initialized to increase the security. See the
for the rationale.
The Linux getrandom() syscall (get random bytes) is now exposed as the new
function. (Contributed by Victor Stinner, part of the
)
pathlib
now supports
. (Contributed by Brett Cannon in
.)
See the summary of
for details.
pdb
The
class constructor has a new optional readrc argument to control whether .pdbrc files should be read.
pickle
Objects that need __new__ called with keyword arguments can now be pickled using
older than protocol version 4. Protocol version 4 already supports this case. (Contributed by Serhiy Storchaka in
.)
pickletools
now outputs the implicit memo index for the MEMOIZE opcode. (Contributed by Serhiy Storchaka in
.)
pydoc
The
module has learned to respect the MANPAGER environment variable. (Contributed by Matthias Klose in
.)
and
can now list named tuple fields in the order they were defined rather than alphabetically. (Contributed by Raymond Hettinger in
.)
random
The new
function returns a list of elements of specified size from the given population with optional weights. (Contributed by Raymond Hettinger in
.)
re
Added support of modifier spans in regular expressions. Examples: '(?i:p)ython' matches 'python' and 'Python', but not 'PYTHON'; '(?i)g(?-i:v)r' matches 'GvR' and 'gvr', but not 'GVR'. (Contributed by Serhiy Storchaka in
.)
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
.)
objects now support
as group indices. (Contributed by Jeroen Demeyer and Xiang Zhang in
.)
readline
Added
to enable or disable automatic addition of input to the history list. (Contributed by Tyler Crompton in
.)
rlcompleter
Private and special attribute names now are omitted unless the prefix starts with underscores. A space or a colon is added after some completed keywords. (Contributed by Serhiy Storchaka in
and
.)
shlex
The
has much
through the new punctuation_chars argument to control which characters are treated as punctuation. (Contributed by Vinay Sajip in
.)
site
When specifying paths to add to
in a .pth file, you may now specify file paths on top of directories (e.g. zip files). (Contributed by Wolfgang Langner in
).
sqlite3
now supports the REPLACE statement. (Contributed by Alex LordThorsen in
.)
socket
The
function now supports the
control code. (Contributed by Daniel Stokes in
.)
The
constants SO_DOMAIN, SO_PROTOCOL, SO_PEERSEC, and SO_PASSSEC are now supported. (Contributed by Christian Heimes in
.)
The
now supports the setsockopt(level,optname,None,optlen:int) form. (Contributed by Christian Heimes in
.)
The socket module now supports the address family
to interface with Linux Kernel crypto API. ALG_*, SOL_ALG and
were added. (Contributed by Christian Heimes in
with support from Victor Stinner.)
New Linux constants TCP_USER_TIMEOUT and TCP_CONGESTION were added. (Contributed by Omar Sandoval,
).
socketserver
Servers based on the
module, including those defined in
,
and
, now support the
protocol. (Contributed by Aviv Palivoda in
.)
The
attribute of
classes now implements the
writable interface. In particular, calling
is now guaranteed to send the data in full. (Contributed by Martin Panter in
.)
ssl
supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in
.)
3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added. (Contributed by Christian Heimes in
and
.)
has better default configuration for options and ciphers. (Contributed by Christian Heimes in
.)
SSL session can be copied from one client-side connection to another with the new
class. TLS session resumption can speed up the initial handshake, reduce latency and improve performance (Contributed by Christian Heimes in
based on a draft by Alex Warhawk.)
The new
method can be used to get a list of enabled ciphers in order of cipher priority.
All constants and flags have been converted to
and
. (Contributed by Christian Heimes in
.)
Server and client-side specific TLS protocols for
were added. (Contributed by Christian Heimes in
.)
Added
ssl.SSLContext.post_handshake_auth
to enable and
ssl.SSLSocket.verify_client_post_handshake()
to initiate TLS 1.3 post-handshake authentication. (Contributed by Christian Heimes in
.)
statistics
A new
function has been added. (Contributed by Steven D’Aprano in
.)
struct
now supports IEEE 754 half-precision floats via the 'e' format specifier. (Contributed by Eli Stevens, Mark Dickinson in
.)
subprocess
destructor now emits a
warning if the child process is still running. Use the context manager protocol (withproc:...) or explicitly call the
method to read the exit status of the child process. (Contributed by Victor Stinner in
.)
The
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
.)
sys
The new
function returns the name of the error mode used to convert between Unicode filenames and bytes filenames. (Contributed by Steve Dower in
.)
On Windows the return value of the
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
.)
telnetlib
telnetlib.Telnet is now a context manager (contributed by Stéphane Wirtel in
).
time
The
attributes tm_gmtoff and tm_zone are now available on all platforms.
timeit
The new
convenience method has been added to call
repeatedly so that the total run time is greater or equal to 200 milliseconds. (Contributed by Steven D’Aprano in
.)
now warns when there is substantial (4x) variance between best and worst times. (Contributed by Serhiy Storchaka in
.)
tkinter
Added methods Variable.trace_add(), Variable.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
).
traceback
Both the traceback module and the interpreter’s builtin exception display now abbreviate long sequences of repeated lines in tracebacks as shown in the following example:
>>> deff():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
.)
tracemalloc
The
module now supports tracing memory allocations in multiple different address spaces.
The new
filter class has been added to filter block traces by their address space (domain).
(Contributed by Victor Stinner in
.)
typing
Since the
module is
, all changes introduced in Python 3.6 have also been backported to Python 3.5.x.
The
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
.)
The
class has been added for representing
contextlib.AbstractContextManager
. (Contributed by Brett Cannon in
.)
The
class has been added for representing
. (Contributed by Ivan Levkivskyi in
.)
The
type construct has been added to mark class variables. As introduced in
, 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
.)
A new
constant that is assumed to be True by the static type checkers, but is False at runtime. (Contributed by Guido van Rossum in
.)
A new
helper function has been added to create lightweight distinct types for annotations:
fromtypingimportNewTypeUserId=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
.)
unicodedata
The
module now uses data from
. (Contributed by Benjamin Peterson.)
unittest.mock
The
class has the following improvements:
Two new methods,
and
to check if the mock object was called. (Contributed by Amit Saha in
.)
The
method now has two optional keyword only arguments: return_value and side_effect. (Contributed by Kushal Das in
.)
urllib.request
If a HTTP request has a file or iterable body (other than a bytes object) but no Content-Length header, rather than throwing an error,
now falls back to use chunked transfer encoding. (Contributed by Demian Brecht and Rolf Krahl in
.)
urllib.robotparser
now supports the Crawl-delay and Request-rate extensions. (Contributed by Nikolay Bogoychev in
.)
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
.)
warnings
A new optional source parameter has been added to the
function: the destroyed object which emitted a
. A source attribute has also been added to warnings.WarningMessage (contributed by Victor Stinner in
and
).
When a
warning is logged, the
module is now used to try to retrieve the traceback where the destroyed object was allocated.
Example with the script example.py:
importwarningsdeffunc():returnopen(__file__)f=func()f=NoneOutput of the command python3.6-Wd-Xtracemalloc=5example.py:
example.py:7:ResourceWarning:unclosedfile<_io.TextIOWrappername='example.py'mode='r'encoding='UTF-8'>f=NoneObjectallocatedat(mostrecentcallfirst):File"example.py",lineno4returnopen(__file__)File"example.py",lineno6f=func()The “Object allocated at” traceback is new and is only displayed if
is tracing Python memory allocations and if the
module was already imported.
winreg
Added the 64-bit integer type
. (Contributed by Clement Rouault in
.)
winsound
Allowed keyword arguments to be passed to
,
, and
(
).
xmlrpc.client
The
module now supports unmarshalling additional data types used by the Apache XML-RPC implementation for numerics and None. (Contributed by Serhiy Storchaka in
.)
zipfile
A new
class method allows making a
instance from a filesystem file. A new
method can be used to check if the ZipInfo instance represents a directory. (Contributed by Thomas Kluyver in
.)
The
method can now be used to write data into a ZIP file, as well as for extracting data. (Contributed by Thomas Kluyver in
.)
zlib
The
and
functions now accept keyword arguments. (Contributed by Aviv Palivoda in
and Xiang Zhang in
respectively.)
Optimizations
The Python interpreter now uses a 16-bit wordcode instead of bytecode which made a number of opcode optimizations possible. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in
and
.)
The
class now has an optimized C implementation. (Contributed by Yury Selivanov and INADA Naoki in
.)
The
class now has an optimized C implementation. (Contributed by Yury Selivanov in
.)
Various implementation improvements in the
module (such as caching of generic types) allow up to 30 times performance improvements and reduced memory footprint.
The ASCII decoder is now up to 60 times as fast for error handlers surrogateescape, ignore and replace (Contributed by Victor Stinner in
).
The ASCII and the Latin1 encoders are now up to 3 times as fast for the error handler surrogateescape (Contributed by Victor Stinner in
).
The UTF-8 encoder is now up to 75 times as fast for error handlers ignore, replace, surrogateescape, surrogatepass (Contributed by Victor Stinner in
).
The UTF-8 decoder is now up to 15 times as fast for error handlers ignore, replace and surrogateescape (Contributed by Victor Stinner in
).
bytes%args is now up to 2 times faster. (Contributed by Victor Stinner in
).
bytearray%args is now between 2.5 and 5 times faster. (Contributed by Victor Stinner in
).
Optimize
and
: they are now between 2x and 3.5x faster. (Contributed by Victor Stinner in
).
Optimize bytes.replace(b'',b'.') and bytearray.replace(b'',b'.'): up to 80% faster. (Contributed by Josh Snider in
).
Allocator functions of the
domain (
) now use the
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
).
and
are now up to 10% faster when deserializing many small objects (Contributed by Victor Stinner in
).
Passing
to a function has an overhead in comparison with passing
. Now in extension functions implemented with using Argument Clinic this overhead is significantly decreased. (Contributed by Serhiy Storchaka in
).
Optimized
and
functions in the
module; they are now about 3–6 times faster. (Contributed by Serhiy Storchaka in
).
Optimized globbing in
by using
; it is now about 1.5–4 times faster. (Contributed by Serhiy Storchaka in
).
parsing, iteration and deepcopy performance has been significantly improved. (Contributed by Serhiy Storchaka in
,
, and
.)
Creation of
instances from floats and decimals is now 2 to 3 times faster. (Contributed by Serhiy Storchaka in
.)
Build and C API Changes
Python now requires some C99 support in the toolchain to build. Most notably, Python now uses standard integer types and macros in place of custom macros like PY_LONG_LONG. For more information, see
and
.
Cross-compiling CPython with the Android NDK and the Android API level set to 21 (Android 5.0 Lollipop) or greater runs successfully. While Android is not yet a supported platform, the Python test suite runs on the Android emulator with only about 16 tests failures. See the Android meta-issue
.
The --enable-optimizations configure flag has been added. Turning it on will activate expensive optimizations like PGO. (Original patch by Alecsandru Patrascu of Intel in
.)
The
must now be held when allocator functions of
(ex:
) and
(ex:
) domains are called.
New
API which indicates if flushing buffered data failed. (Contributed by Martin Panter in
.)
now supports
. Positional-only parameters are defined by empty names. (Contributed by Serhiy Storchaka in
).
PyTraceback_Print method now abbreviates long sequences of repeated lines as "[Previouslinerepeated{count}moretimes]". (Contributed by Emanuel Barry in
.)
The new
PyErr_SetImportErrorSubclass()
function allows for specifying a subclass of
to raise. (Contributed by Eric Snow in
.)
The new
function can be used to generate a
providing the source of the resource allocation. (Contributed by Victor Stinner in
.)
The new
function returns the file system representation of a
. (Contributed by Brett Cannon in
.)
The
and
functions will now accept
.
Other Improvements
When
(short form:
) is supplied twice, Python prints
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)]
Deprecated
New Keywords
async and await are not recommended to be used as variable, class, function or module names. Introduced by
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
.
Deprecated Python behavior
Raising the
exception inside a generator will now generate a
, and will trigger a
in Python 3.7. See
PEP 479: Change StopIteration handling inside generators
for details.
The
method is now expected to return an asynchronous iterator directly instead of returning an awaitable as previously. Doing the former will trigger a
. Backward compatibility will be removed in Python 3.7. (Contributed by Yury Selivanov in
.)
A backslash-character pair that is not a valid escape sequence now generates a
. Although this will eventually become a
, that will not be for several Python releases. (Contributed by Emanuel Barry in
.)
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
. (Contributed by Rose Ames in
.)
Deprecated Python modules, functions and methods
asynchat
The asynchat has been deprecated in favor of
. (Contributed by Mariatta in
.)
asyncore
The asyncore has been deprecated in favor of
. (Contributed by Mariatta in
.)
dbm
Unlike other
implementations, the
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
.)
distutils
The undocumented extra_path argument to the distutils.Distribution constructor is now considered deprecated and will raise a warning if set. Support for this parameter will be removed in a future Python release. See
for details.
grp
The support of non-integer arguments in
has been deprecated. (Contributed by Serhiy Storchaka in
.)
importlib
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
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
by default (on Windows), but this may change in future releases.
os
Undocumented support of general
as paths in
functions,
and similar functions is now deprecated. (Contributed by Serhiy Storchaka in
and
.)
re
Support for inline flags (?letters) in the middle of the regular expression has been deprecated and will be removed in a future Python version. Flags at the start of a regular expression are still allowed. (Contributed by Serhiy Storchaka in
.)
ssl
OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported. In the future the
module will require at least OpenSSL 1.0.2 or 1.1.0.
SSL-related arguments like certfile, keyfile and check_hostname in
,
,
,
, and
have been deprecated in favor of context. (Contributed by Christian Heimes in
.)
A couple of protocols and functions of the
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
and
.)
tkinter
The tkinter.tix module is now deprecated.
users should use
instead.
venv
The pyvenv script has been deprecated in favour of python3-mvenv. This prevents confusion as to what Python interpreter pyvenv is connected to and thus what Python interpreter will be used by the virtual environment. (Contributed by Brett Cannon in
.)
xml
As mitigation against DTD and external entity retrieval, the
and
modules no longer process external entities by default. (Contributed by Christian Heimes in
.)
Deprecated functions and types of the C API
Undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsEncodedUnicode() and PyUnicode_AsDecodedUnicode() are deprecated now. Use the
instead.
Deprecated Build Options
The --with-system-ffi configure flag is now on by default on non-macOS UNIX platforms. It may be disabled by using --without-system-ffi, but using the flag is deprecated and will not be accepted in Python 3.7. macOS is unaffected by this change. Note that many OS distributors already use the --with-system-ffi flag when building their system Python.
Removed
API and Feature Removals
Unknown escapes consisting of '\' and an ASCII letter in regular expressions will now cause an error. In replacement templates for
they are still allowed, but deprecated. The
flag can now only be used with binary patterns.
inspect.getmoduleinfo() was removed (was deprecated since CPython 3.3).
should be used for obtaining the module name for a given path. (Contributed by Yury Selivanov in
.)
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
module. They were undocumented methods deprecated since Python 3.2 and equivalent functionality is available from private methods.
The tk_menuBar() and tk_bindForTraversal() dummy methods in
widget classes were removed (corresponding Tk commands were obsolete since Tk 4.0).
The
method of the
class no longer supports the 'U' mode (was deprecated since Python 3.4). Use
for reading compressed text files in
mode.
The undocumented IN, CDROM, DLFCN, TYPES, CDIO, and STROPTS modules have been removed. They had been available in the platform specific Lib/plat-*/ directories, but were chronically out of date, inconsistently available across platforms, and unmaintained. The script that created these modules is still available in the source distribution at
.
The deprecated asynchat.fifo class has been removed.
Porting to Python 3.6
This section lists previously described changes and other bugfixes that may require changes to your code.
Changes in ‘python’ Command Behavior
The output of a special Python build with defined COUNT_ALLOCS, SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default. It can be re-enabled using the -Xshowalloccount option. It now outputs to stderr instead of stdout. (Contributed by Serhiy Storchaka in
.)
Changes in the Python API
will no longer allow combining the 'U' mode flag with '+'. (Contributed by Jeff Balogh and John O’Connor in
.)
no longer implicitly commits an open transaction before DDL statements.
On Linux,
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.
now sets
when its msg argument is not set. Previously only NULL was returned.
The format of the codeobject.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
, 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
for the rationale.
The functions in the
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
.
Reading the port attribute of
and
results now raises
for out-of-range values, rather than returning
. See
.
The imp module now raises a
instead of
.
The following modules have had missing APIs added to their
attributes to match the documented APIs:
, cgi,
,
,
,
,
,
,
,
,
,
, smtpd,
,
,
and
. This means they will export new symbols when import* is used. (Contributed by Joel Taddei and Jacek Kołodziej in
.)
When performing a relative import, if __package__ does not compare equal to __spec__.parent then
is raised. (Contributed by Brett Cannon in
.)
When a relative import is performed and no parent package is known, then
will be raised. Previously,
could be raised. (Contributed by Brett Cannon in
.)
Servers based on the
module, including those defined in
,
and
, now only catch exceptions derived from
. Therefore if a request handler raises an exception like
or
,
is no longer called, and the exception will stop a single-threaded server. (Contributed by Martin Panter in
.)
spwd.getspnam() now raises a
instead of
if the user doesn’t have privileges.
The
method now raises an exception if an error (e.g. EBADF) was reported by the underlying system call. (Contributed by Martin Panter in
.)
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
,
,
and
functions and
and
class constructors in the
module are now
. (Contributed by Serhiy Storchaka in
.)
Subclasses of
which don’t override type.__new__ may no longer use the one-argument form to get the type of an object.
As part of
, the handling of keyword arguments passed to
(other than the metaclass hint, metaclass) is now consistently delegated to
. This means that
and
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
) 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=zipThis behavior has also been backported to earlier Python versions by Setuptools 26.0.0.
In the
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
.)
The
now returns rows of type
. (Contributed by Steve Holden in
.)
The crypt.METHOD_CRYPT will no longer be added to crypt.methods if unsupported by the platform. (Contributed by Victor Stinner in
.)
The verbose and rename arguments for
are now keyword-only. (Contributed by Raymond Hettinger in
.)
On Linux,
now looks in LD_LIBRARY_PATH for shared libraries. (Contributed by Vinay Sajip in
.)
The
class now handles flags containing the ']' character in messages sent from the server to improve real-world compatibility. (Contributed by Lita Cho in
.)
The
function now returns the number of bytes written like other write methods. (Contributed by Jakub Stasiak in
.)
The
and
functions now return
named tuples. (Contributed by Ramchandra Apte in
.)
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
.)
will now raise
for unrecognized compression values. Previously a plain
was raised. Additionally, calling ZipFile methods on a closed ZipFile or calling the
method on a ZipFile created with mode 'r' will raise a
. Previously, a RuntimeError was raised in those scenarios.
when custom metaclasses are combined with zero-argument
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
in Python 3.6 and a
in Python 3.8.
With the introduction of
, import system consumers may start expecting import system replacements to raise that more specific exception when appropriate, rather than the less-specific
. To provide future compatibility with such consumers, implementers of alternative import systems that completely replace
will need to update their implementations to raise the new subclass when a module can’t be found at all. Implementers of compliant plugins to the default import system shouldn’t need to make any changes, as the default import system will raise the new subclass when appropriate.
Changes in the C API
The
allocator family now uses the
rather than the system malloc(). Applications calling PyMem_Malloc() without holding the GIL can now crash. Set the
environment variable to debug to validate the usage of memory allocators in your application. See
.
(and the main interpreter) now override the exit status with 120 if flushing buffered data failed. See
.
CPython bytecode changes
There have been several major changes to the
in Python 3.6.
The Python interpreter now uses a 16-bit wordcode instead of bytecode. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in
and
.)
The new FORMAT_VALUE and
opcodes as part of the
implementation. (Contributed by Eric Smith in
and Serhiy Storchaka in
.)
The new BUILD_CONST_KEY_MAP opcode to optimize the creation of dictionaries with constant keys. (Contributed by Serhiy Storchaka in
.)
The function call opcodes have been heavily reworked for better performance and simpler implementation. The
, CALL_FUNCTION, CALL_FUNCTION_KW and BUILD_MAP_UNPACK_WITH_CALL opcodes have been modified, the new
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
, and Serhiy Storchaka in
,
.)
The new
and STORE_ANNOTATION opcodes have been added to support the new
syntax. (Contributed by Ivan Levkivskyi in
.)
Notable changes in Python 3.6.2
New makeregen-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 makeregen-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
for details.
(Contributed by Victor Stinner in
.)
Added in version 3.6.2.
Removal of maketouch build target
The maketouch 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 makeregen-all target.
(Contributed by Victor Stinner in
.)
Changed in version 3.6.2.
Notable changes in Python 3.6.4
The PyExc_RecursionErrorInst singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter. (Contributed by Xavier de Gaye in
and
.)
Notable changes in Python 3.6.5
The
function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale in some cases. (Contributed by Victor Stinner in
.)
Notable changes in Python 3.6.7
and
modules no longer process external entities by default. See also
.
In 3.6.7 the
module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. (Contributed by Ammar Askar in
.)
Notable changes in Python 3.6.10
Due to significant security concerns, the reuse_address parameter of
asyncio.loop.create_datagram_endpoint()
is no longer supported. This is because of the behavior of the socket option SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
.)
Notable changes in Python 3.6.13
Earlier Python versions allowed using both ; and & as query parameter separators in
and
. Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with & as the default. This change also affects cgi.parse() and cgi.parse_multipart() as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in
.)
Notable changes in Python 3.6.14
A security fix alters the
behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a trust_server_pasv_ipv4_address attribute on your FTP instance to True. (See
)
The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986, ASCII newline \n, \r and tab \t characters are stripped from the URL by the parser
preventing such attacks. The removal characters are controlled by a new module level variable urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (See
)