What’s New In Python 3.5
Release: | 3.5.0rc3 |
---|---|
Date: | September 06, 2015 |
This article explains the new features in Python 3.5, compared to 3.4.
For full details, see the Misc/NEWS file.
Note
Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.5 moves towards release, so it’s worth checking back even after reading earlier versions.
See also
PEP 478 - Python 3.5 Release Schedule
Summary – Release highlights
New syntax features:
- PEP 465, a new matrix multiplication operator:
a @ b
. - PEP 492, coroutines with async and await syntax.
- PEP 448, additional unpacking generalizations.
New library modules:
New built-in features:
bytes % args
,bytearray % args
: PEP 461 - Adding%
formatting to bytes and bytearrayb'\xf0\x9f\x90\x8d'.hex()
,bytearray(b'\xf0\x9f\x90\x8d').hex()
,memoryview(b'\xf0\x9f\x90\x8d').hex()
: issue 9951 - Ahex
method has been added to bytes, bytearray, and memoryview.- Generators have new
gi_yieldfrom
attribute, which returns the object being iterated byyield from
expressions. (Contributed by Benno Leslie and Yury Selivanov in issue 24450.) - New
RecursionError
exception. (Contributed by Georg Brandl in issue 19235.)
Implementation improvements:
- When the
LC_TYPE
locale is the POSIX locale (C
locale),sys.stdin
andsys.stdout
are now using thesurrogateescape
error handler, instead of thestrict
error handler (issue 19977). - PEP 488, the elimination of
.pyo
files. - PEP 489, multi-phase initialization of extension modules.
Significantly Improved Library Modules:
collections.OrderedDict
is now implemented in C, which improves its performance between 4x to 100x times. Contributed by Eric Snow in issue 16991.- You may now pass bytes to the
tempfile
module’s APIs and it will return the temporary pathname as bytes instead of str. It also accepts a value ofNone
on parameters where only str was accepted in the past to do the right thing based on the types of the other inputs. Two functions,gettempdirb()
andgettempprefixb()
, have been added to go along with this. This behavior matches that of theos
APIs. ssl
module gained support for Memory BIO, which decouples SSL protocol handling from network IO. (Contributed by Geert Jansen in issue 21965.)
Security improvements:
- None yet.
Windows improvements:
- A new installer for Windows has replaced the old MSI. See Using Python on Windows for more information.
- Windows builds now use Microsoft Visual C++ 14.0, and extension modules should use the same.
Please read on for a comprehensive list of user-facing changes.
PEP 492 - Coroutines with async and await syntax
The PEP added dedicated syntax for declaring coroutines,
await
expressions, new asynchronous async for
and async with
statements.
Example:
async def read_data(db):
async with db.transaction():
data = await db.fetch('SELECT ...')
PEP written and implemented by Yury Selivanov.
See also
PEP 492 – Coroutines with async and await syntax
PEP 461 - Formatting support for bytes and bytearray
This PEP proposes adding % formatting operations similar to Python 2’s str
type to bytes
and bytearray
.
Examples:
>>> b'Hello %s!' % b'World'
b'Hello World!'
>>> b'x=%i y=%f' % (1, 2.5)
b'x=1 y=2.500000'
Unicode is not allowed for %s
, but it is accepted by %a
(equivalent of
repr(obj).encode('ascii', 'backslashreplace')
):
>>> b'Hello %s!' % 'World'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: %b requires bytes, or an object that implements __bytes__, not 'str'
>>> b'price: %a' % '10€'
b"price: '10\\u20ac'"
See also
PEP 461 – Adding % formatting to bytes and bytearray
PEP 465 - A dedicated infix operator for matrix multiplication
This PEP proposes a new binary operator to be used for matrix multiplication,
called @
. (Mnemonic: @
is *
for mATrices.)
See also
PEP 465 – A dedicated infix operator for matrix multiplication
PEP 448 - Additional Unpacking Generalizations
This PEP proposes extended usages of the *
iterable unpacking
operator and **
dictionary unpacking operators
to allow unpacking in more positions, an arbitrary number of
times, and in additional circumstances. Specifically,
in function calls, in comprehensions and generator expressions, and
in displays.
Function calls are proposed to support an arbitrary number of unpackings rather than just one:
>>> print(*[1], *[2], 3)
1 2 3
>>> dict(**{'x': 1}, y=2, **{'z': 3})
{'x': 1, 'y': 2, 'z': 3}
Unpacking is proposed to be allowed inside tuple, list, set, and dictionary displays:
>>> *range(4), 4
(0, 1, 2, 3, 4)
>>> [*range(4), 4]
[0, 1, 2, 3, 4]
>>> {*range(4), 4}
{0, 1, 2, 3, 4}
>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}
In dictionaries, later values will always override earlier ones:
>>> {'x': 1, **{'x': 2}}
{'x': 2}
>>> {**{'x': 2}, 'x': 1}
{'x': 1}
See also
PEP 448 – Additional Unpacking Generalizations
PEP 484 - Type Hints
This PEP introduces a provisional module to provide these standard definitions and tools, along with some conventions for situations where annotations are not available.
For example, here is a simple function whose argument and return type are declared in the annotations:
def greeting(name: str) -> str:
return 'Hello ' + name
The type system supports unions, generic types, and a special type
named Any
which is consistent with (i.e. assignable to and from) all
types.
PEP 471 - os.scandir() function – a better and faster directory iterator
PEP 471 adds a new directory iteration function, os.scandir()
,
to the standard library. Additionally, os.walk()
is now
implemented using os.scandir()
, which speeds it up by 3-5 times
on POSIX systems and by 7-20 times on Windows systems.
PEP and implementation written by Ben Hoyt with the help of Victor Stinner.
See also
PEP 471 – os.scandir() function – a better and faster directory iterator
PEP 475: Retry system calls failing with EINTR
PEP 475 adds support for automatic retry of system calls failing with
EINTR
: this means that user code doesn’t have to deal with
EINTR or InterruptedError
manually, and should make it more robust
against asynchronous signal reception.
Examples of functions which are now retried when interrupted by a signal
instead of raising InterruptedError
if the Python signal handler does
not raise an exception:
open()
,os.open()
,io.open()
- functions of the
faulthandler
module os
functions:os.fchdir()
os.fchmod()
os.fchown()
os.fdatasync()
os.fstat()
os.fstatvfs()
os.fsync()
os.ftruncate()
os.mkfifo()
os.mknod()
os.posix_fadvise()
os.posix_fallocate()
os.pread()
os.pwrite()
os.read()
os.readv()
os.sendfile()
os.wait3()
os.wait4()
os.wait()
os.waitid()
os.waitpid()
os.write()
os.writev()
- special cases:
os.close()
andos.dup2()
now ignoreEINTR
error, the syscall is not retried (see the PEP for the rationale)
select
functions:socket.socket()
methods:signal.sigtimedwait()
,signal.sigwaitinfo()
time.sleep()
PEP and implementation written by Charles-François Natali and Victor Stinner, with the help of Antoine Pitrou (the french connection).
See also
PEP 475 – Retry system calls failing with EINTR
PEP 479: Change StopIteration handling inside generators
PEP 479 changes the behavior of generators: when a StopIteration
exception is raised inside a generator, it is replaced with a
RuntimeError
. To enable the feature a __future__
import should
be used:
from __future__ import generator_stop
Without a __future__
import, a PendingDeprecationWarning
will be
raised.
PEP written by Chris Angelico and Guido van Rossum. Implemented by Chris Angelico, Yury Selivanov and Nick Coghlan.
See also
PEP 479 – Change StopIteration handling inside generators
PEP 486: Make the Python Launcher aware of virtual environments
PEP 486 makes the Windows launcher (see PEP 397) aware of an active
virtual environment. When the default interpreter would be used and the
VIRTUAL_ENV
environment variable is set, the interpreter in the virtual
environment will be used.
See also
PEP 486 – Make the Python Launcher aware of virtual environments
PEP 488: Elimination of PYO files
PEP 488 does away with the concept of .pyo
files. This means that
.pyc
files represent both unoptimized and optimized bytecode. To prevent the
need to constantly regenerate bytecode files, .pyc
files now have an
optional opt-
tag in their name when the bytecode is optimized. This has the
side-effect of no more bytecode file name clashes when running under either
-O
or -OO
. Consequently, bytecode files generated from -O
, and
-OO
may now exist simultaneously. importlib.util.cache_from_source()
has an updated API to help with this change.
See also
PEP 488 – Elimination of PYO files
PEP 489: Multi-phase extension module initialization
PEP 489 updates extension module initialization to take advantage of the two step module loading mechanism introduced by PEP 451 in Python 3.4.
This change brings the import semantics of extension modules that opt-in to using the new mechanism much closer to those of Python source and bytecode modules, including the ability to use any valid identifier as a module name, rather than being restricted to ASCII.
See also
PEP 488 – Multi-phase extension module initialization
PEP 485: A function for testing approximate equality
PEP 485 adds the math.isclose()
and cmath.isclose()
functions which tell whether two values are approximately equal or
“close” to each other. Whether or not two values are considered
close is determined according to given absolute and relative tolerances.
See also
PEP 485 – A function for testing approximate equality
Other Language Changes
Some smaller changes made to the core Python language are:
- Added the
'namereplace'
error handlers. The'backslashreplace'
error handlers now works with decoding and translating. (Contributed by Serhiy Storchaka in issue 19676 and issue 22286.) - The
-b
option now affects comparisons ofbytes
withint
. (Contributed by Serhiy Storchaka in issue 23681) - New Kazakh codec
kz1048
. (Contributed by Serhiy Storchaka in issue 22682.) - Property docstrings are now writable. This is especially useful for
collections.namedtuple()
docstrings. (Contributed by Berker Peksag in issue 24064.) - New Tajik codec
koi8_t
. (Contributed by Serhiy Storchaka in issue 22681.)
New Modules
zipapp
The new zipapp
module (specified in PEP 441) provides an API and
command line tool for creating executable Python Zip Applications, which
were introduced in Python 2.6 in issue 1739468 but which were not well
publicised, either at the time or since.
With the new module, bundling your application is as simple as putting all
the files, including a __main__.py
file, into a directory myapp
and running:
$ python -m zipapp myapp
$ python myapp.pyz
Improved Modules
argparse
ArgumentParser
now allows to disable abbreviated usage of long options by setting allow_abbrev toFalse
. (Contributed by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.)
cgi
FieldStorage
now supports the context management protocol. (Contributed by Berker Peksag in issue 20289.)
cmath
cmath.isclose()
function added. (Contributed by Chris Barker and Tal Einat in issue 24270.)
code
- The
code.InteractiveInterpreter.showtraceback()
method now prints the full chained traceback, just like the interactive interpreter. (Contributed by Claudiu Popa in issue 17442.)
collections
You can now update docstrings produced by
collections.namedtuple()
:Point = namedtuple('Point', ['x', 'y']) Point.__doc__ = 'ordered pair' Point.x.__doc__ = 'abscissa' Point.y.__doc__ = 'ordinate'
(Contributed by Berker Peksag in issue 24064.)
compileall
compileall.compile_dir()
andcompileall
‘s command-line interface can now do parallel bytecode compilation. (Contributed by Claudiu Popa in issue 16104.)
contextlib
- The new
contextlib.redirect_stderr()
context manager(similar tocontextlib.redirect_stdout()
) makes it easier for utility scripts to handle inflexible APIs that write their output tosys.stderr
and don’t provide any options to redirect it. (Contributed by Berker Peksag in issue 22389.)
curses
- The new
curses.update_lines_cols()
function updates the variablescurses.LINES
andcurses.COLS
.
difflib
- The charset of the HTML document generated by
difflib.HtmlDiff.make_file()
can now be customized by using charset keyword-only parameter. The default charset of HTML document changed from'ISO-8859-1'
to'utf-8'
. (Contributed by Berker Peksag in issue 2052.) - It’s now possible to compare lists of byte strings with
difflib.diff_bytes()
(fixes a regression from Python 2).
distutils
- The
build
andbuild_ext
commands now accept a-j
option to enable parallel building of extension modules. (Contributed by Antoine Pitrou in issue 5309.) - Added support for the LZMA compression. (Contributed by Serhiy Storchaka in issue 16314.)
doctest
doctest.DocTestSuite()
returns an emptyunittest.TestSuite
if module contains no docstrings instead of raisingValueError
. (Contributed by Glenn Jones in issue 15916.)
- A new policy option
mangle_from_
controls whether or not lines that start with “From ” in email bodies are prefixed with a ‘>’ character by generators. The default isTrue
forcompat32
andFalse
for all other policies. (Contributed by Milan Oberkirch in issue 20098.) - A new method
get_content_disposition()
provides easy access to a canonical value for the Content-Disposition header (None
if there is no such header). (Contributed by Abhilash Raj in issue 21083.) - A new policy option
utf8
can be setTrue
to encode email headers using the utf8 charset instead of using encoded words. This allowsMessages
to be formatted according to RFC 6532 and used with an SMTP server that supports the RFC 6531SMTPUTF8
extension. (Contributed by R. David Murray in issue 24211.)
glob
iglob()
andglob()
now support recursive search in subdirectories using the “**
” pattern. (Contributed by Serhiy Storchaka in issue 13968.)
idlelib and IDLE
Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release. See
Lib/idlelib/NEWS.txt
for a cumulative list of changes since 3.4.0,
as well as changes made in future 3.5.x releases. This file is also available
from the IDLE Help -> About Idle dialog.
imaplib
IMAP4
now supports the context management protocol. When used in awith
statement, the IMAP4LOGOUT
command will be called automatically at the end of the block. (Contributed by Tarek Ziadé and Serhiy Storchaka in issue 4972.)imaplib
now supports RFC 5161: theenable()
extension), and RFC 6855: utf-8 support (internationalized email, via theUTF8=ACCEPT
argument toenable()
). A new attribute,utf8_enabled
, tracks whether or not RFC 6855 support is enabled. Milan Oberkirch, R. David Murray, and Maciej Szulik in issue 21800.)imaplib
now automatically encodes non-ASCII string usernames and passwords usingUTF8
, as recommended by the RFCs. (Contributed by Milan Oberkirch in issue 21800.)
imghdr
what()
now recognizes the OpenEXR format. (Contributed by Martin Vignali and Claudiu Popa in issue 20295.)
importlib
importlib.util.LazyLoader
allows for the lazy loading of modules in applications where startup time is paramount. (Contributed by Brett Cannon in issue 17621.)importlib.abc.InspectLoader.source_to_code()
is now a static method to make it easier to work with source code in a string. With a module object that you want to initialize you can then useexec(code, module.__dict__)
to execute the code in the module.importlib.util.module_from_spec()
is now the preferred way to create a new module. Compared totypes.ModuleType
, this new function will set the various import-controlled attributes based on the passed-in spec object.
inspect
inspect.Signature
andinspect.Parameter
are now picklable and hashable. (Contributed by Yury Selivanov in issue 20726 and issue 20334.)- New method
inspect.BoundArguments.apply_defaults()
. (Contributed by Yury Selivanov in issue 24190.) - New class method
inspect.Signature.from_callable()
, which makes subclassing ofSignature
easier. (Contributed by Yury Selivanov and Eric Snow in issue 17373.) - New argument
follow_wrapped
forinspect.signature()
. (Contributed by Yury Selivanov in issue 20691.) - New
iscoroutine()
,iscoroutinefunction()
andisawaitable()
functions. (Contributed by Yury Selivanov in issue 24017.) - New
getcoroutinelocals()
andgetcoroutinestate()
functions. (Contributed by Yury Selivanov in issue 24400.)
ipaddress
ipaddress.IPv4Network
andipaddress.IPv6Network
now accept an(address, netmask)
tuple argument, so as to easily construct network objects from existing addresses. (Contributed by Peter Moody and Antoine Pitrou in issue 16531.)
json
- The output of
json.tool
command line interface is now in the same order as the input. Use the--sort-keys
option to sort the output of dictionaries alphabetically by key. (Contributed by Berker Peksag in issue 21650.) - JSON decoder now raises
json.JSONDecodeError
instead ofValueError
. (Contributed by Serhiy Storchaka in issue 19361.)
math
math.inf
andmath.nan
constants added. (Contributed by Mark Dickinson in issue 23185.)math.isclose()
function added. (Contributed by Chris Barker and Tal Einat in issue 24270.)
os
- New
os.scandir()
function that exposes file information from the operating system when listing a directory.os.scandir()
returns an iterator ofos.DirEntry
objects corresponding to the entries in the directory given by path. (Contributed by Ben Hoyt with the help of Victor Stinner in issue 22524.) os.stat_result
now has ast_file_attributes
attribute on Windows. (Contributed by Ben Hoyt in issue 21719.)os.urandom()
: On Linux 3.17 and newer, thegetrandom()
syscall is now used when available. On OpenBSD 5.6 and newer, the Cgetentropy()
function is now used. These functions avoid the usage of an internal file descriptor.
os.path
- New
commonpath()
function that extracts common path prefix. Unlike thecommonprefix()
function, it always returns a valid path. (Contributed by Rafik Draoui and Serhiy Storchaka in issue 10395.)
pickle
- Serializing more “lookupable” objects (such as unbound methods or nested classes) now are supported with pickle protocols < 4. (Contributed by Serhiy Storchaka in issue 23611.)
poplib
- A new command
utf8()
enables RFC 6856 (internationalized email) support if the POP server supports it. (Contributed by Milan OberKirch in issue 21804.)
re
- Number of capturing groups in regular expression is no longer limited by 100. (Contributed by Serhiy Storchaka in issue 22437.)
- Now unmatched groups are replaced with empty strings in
re.sub()
andre.subn()
. (Contributed by Serhiy Storchaka in issue 1519638.)
shutil
move()
now accepts a copy_function argument, allowing, for example,copy()
to be used instead of the defaultcopy2()
if there is a need to ignore metadata. (Contributed by Claudiu Popa in issue 19840.)
signal
- On Windows,
signal.set_wakeup_fd()
now also supports socket handles. (Contributed by Victor Stinner in issue 22018.) - Different constants of
signal
module are now enumeration values using theenum
module. This allows meaningful names to be printed during debugging, instead of integer “magic numbers”. (Contributed by Giampaolo Rodola’ in issue 21076.)
smtpd
- Both
SMTPServer
andsmtpd.SMTPChannel
now accept a decode_data keyword to determine if the DATA portion of the SMTP transaction is decoded using theutf-8
codec or is instead provided toprocess_message()
as a byte string. The default isTrue
for backward compatibility reasons, but will change toFalse
in Python 3.6. If decode_data is set toFalse
, theprocess_message()
method must be prepared to accept keyword arguments. (Contributed by Maciej Szulik in issue 19662.) SMTPServer
now advertises the8BITMIME
extension (RFC 6152) if if decode_data has been setTrue
. If the client specifiesBODY=8BITMIME
on theMAIL
command, it is passed toprocess_message()
via themail_options
keyword. (Contributed by Milan Oberkirch and R. David Murray in issue 21795.)SMTPServer
now supports theSMTPUTF8
extension (RFC 6531: Internationalized Email). If the client specifiedSMTPUTF8 BODY=8BITMIME
on theMAIL
command, they are passed toprocess_message()
via themail_options
keyword. It is the responsibility of theprocess_message()
method to correctly handle theSMTPUTF8
data. (Contributed by Milan Oberkirch in issue 21725.)- It is now possible to provide, directly or via name resolution, IPv6
addresses in the
SMTPServer
constructor, and have it successfully connect. (Contributed by Milan Oberkirch in issue 14758.)
smtplib
- A new
auth()
method provides a convenient way to implement custom authentication mechanisms. (Contributed by Milan Oberkirch in issue 15014.) - Additional debuglevel (2) shows timestamps for debug messages in
smtplib.SMTP
. (Contributed by Gavin Chappell and Maciej Szulik in issue 16914.) smtplib
now supports RFC 6531 (SMTPUTF8) in both thesendmail()
andsend_message()
commands. (Contributed by Milan Oberkirch and R. David Murray in issue 22027.)
sndhdr
what()
andwhathdr()
now returnnamedtuple()
. (Contributed by Claudiu Popa in issue 18615.)
ssl
- The
do_handshake()
,read()
,shutdown()
, andwrite()
methods ofssl.SSLSocket
don’t reset the socket timeout anymore each time bytes are received or sent. The socket timeout is now the maximum total duration of the method. - Memory BIO Support: new classes
SSLObject
,MemoryBIO
, and newSSLContext.wrap_bio
method. (Contributed by Geert Jansen in issue 21965.)
socket
- New
socket.socket.sendfile()
method allows to send a file over a socket by using high-performanceos.sendfile()
function on UNIX resulting in uploads being from 2x to 3x faster than when using plainsocket.socket.send()
. (Contributed by Giampaolo Rodola’ in issue 17552.) - The
socket.socket.sendall()
method don’t reset the socket timeout anymore each time bytes are received or sent. The socket timeout is now the maximum total duration to send all data.
subprocess
- The new
subprocess.run()
function runs subprocesses and returns asubprocess.CompletedProcess
object. It Provides a more consistent API thancall()
,check_call()
andcheck_output()
.
sys
- New
set_coroutine_wrapper()
andget_coroutine_wrapper()
functions. (Contributed by Yury Selivanov in issue 24017.)
sysconfig
- The user scripts directory on Windows is now versioned. (Contributed by Paul Moore in issue 23437.)
tarfile
- The
tarfile.open()
function now supports'x'
(exclusive creation) mode. (Contributed by Berker Peksag in issue 21717.) - The
extractall()
andextract()
methods now take a keyword parameter numeric_only. If set toTrue
, the extracted files and directories will be owned by the numeric uid and gid from the tarfile. If set toFalse
(the default, and the behavior in versions prior to 3.5), they will be owned bythe named user and group in the tarfile. (Contributed by Michael Vogt and Eric Smith in issue 23193.)
time
- The
time.monotonic()
function is now always available. (Contributed by Victor Stinner in issue 22043.)
tkinter
- The
tkinter._fix
module used for setting up the Tcl/Tk environment on Windows has been replaced by a private function in the_tkinter
module which makes no permanent changes to environment variables. (Contributed by Zachary Ware in issue 20035.)
types
- New
coroutine()
function. (Contributed by Yury Selivanov in issue 24017.) - New
CoroutineType
. (Contributed by Yury Selivanov in issue 24400.)
urllib
- A new
HTTPPasswordMgrWithPriorAuth
allows HTTP Basic Authentication credentials to be managed so as to eliminate unnecessary401
response handling, or to unconditionally send credentials on the first request in order to communicate with servers that return a404
response instead of a401
if theAuthorization
header is not sent. (Contributed by Matej Cepl in issue 19494 and Akshit Khurana in issue 7159.) - A new
urlencode()
parameter quote_via provides a way to control the encoding of query parts if needed. (Contributed by Samwyse and Arnon Yaari in issue 13866.)
unicodedata
- The
unicodedata
module now uses data from Unicode 8.0.0.
wsgiref
- headers parameter of
wsgiref.headers.Headers
is now optional. (Contributed by Pablo Torres Navarrete and SilentGhost in issue 5800.)
xmlrpc
xmlrpc.client.ServerProxy
is now a context manager. (Contributed by Claudiu Popa in issue 20627.)
xml.sax
- SAX parsers now support a character stream of
InputSource
object. (Contributed by Serhiy Storchaka in issue 2175.)
faulthandler
enable()
,register()
,dump_traceback()
anddump_traceback_later()
functions now accept file descriptors. (Contributed by Wei Wu in issue 23566.)
zipfile
- Added support for writing ZIP files to unseekable streams. (Contributed by Serhiy Storchaka in issue 23252.)
- The
zipfile.ZipFile.open()
function now supports'x'
(exclusive creation) mode. (Contributed by Serhiy Storchaka in issue 21717.)
Optimizations
The following performance enhancements have been added:
os.walk()
has been sped up by 3-5x on POSIX systems and 7-20x on Windows. This was done using the newos.scandir()
function, which exposes file information from the underlyingreaddir
andFindFirstFile
/FindNextFile
system calls. (Contributed by Ben Hoyt with help from Victor Stinner in issue 23605.)- Construction of
bytes(int)
(filled by zero bytes) is faster and uses less memory for large objects.calloc()
is used instead ofmalloc()
to allocate memory for these objects. - Some operations on
IPv4Network
andIPv6Network
have been massively sped up, such assubnets()
,supernet()
,summarize_address_range()
,collapse_addresses()
. The speed up can range from 3x to 15x. (issue 21486, issue 21487, issue 20826) - Many operations on
io.BytesIO
are now 50% to 100% faster. (Contributed by Serhiy Storchaka in issue 15381 and David Wilson in issue 22003.) marshal.dumps()
is now faster (65%-85% with versions 3–4, 20-25% with versions 0–2 on typical data, and up to 5x in best cases). (Contributed by Serhiy Storchaka in issue 20416 and issue 23344.)- The UTF-32 encoder is now 3x to 7x faster. (Contributed by Serhiy Storchaka in issue 15027.)
Build and C API Changes
Changes to Python’s build process and to the C API include:
- New
calloc
functions:PyMem_RawCalloc()
PyMem_Calloc()
PyObject_Calloc()
_PyObject_GC_Calloc()
- Windows builds now require Microsoft Visual C++ 14.0, which is available as part of Visual Studio 2015.
Deprecated
New Keywords
async
and await
are not recommended to be used as variable, class,
function or module names. Introduced by PEP 492 in Python 3.5, they will
become proper keywords in Python 3.7.
Unsupported Operating Systems
- Windows XP - Per PEP 11, Microsoft support of Windows XP has ended.
Deprecated Python modules, functions and methods
- The
formatter
module has now graduated to full deprecation and is still slated for removal in Python 3.6. smtpd
has in the past always decoded the DATA portion of email messages using theutf-8
codec. This can now be controlled by the new decode_data keyword toSMTPServer
. The default value isTrue
, but this default is deprecated. Specify the decode_data keyword with an appropriate value to avoid the deprecation warning.- Directly assigning values to the
key
,value
andcoded_value
ofMorsel
objects is deprecated. Use theset()
method instead. In addition, the undocumented LegalChars parameter ofset()
is deprecated, and is now ignored. - Passing a format string as keyword argument format_string to the
format()
method of thestring.Formatter
class has been deprecated. platform.dist()
andplatform.linux_distribution()
functions are now deprecated and will be removed in Python 3.7. Linux distributions use too many different ways of describing themselves, so the functionality is left to a package. (Contributed by Vajrasky Kok and Berker Peksag in issue 1322.)- The previously undocumented
from_function
andfrom_builtin
methods ofinspect.Signature
are deprecated. Use newinspect.Signature.from_callable()
instead. (Contributed by Yury Selivanov in issue 24248.) inspect.getargspec()
is deprecated and scheduled to be removed in Python 3.6. (See issue 20438 for details.)getfullargspec()
,getargvalues()
,getcallargs()
,getargvalues()
,formatargspec()
, andformatargvalues()
are deprecated in favor ofinspect.signature()
API. (See issue 20438 for details.)
Deprecated functions and types of the C API
- None yet.
Deprecated features
- None yet.
Removed
API and Feature Removals
The following obsolete and previously deprecated APIs and features have been removed:
- The
__version__
attribute has been dropped from the email package. The email code hasn’t been shipped separately from the stdlib for a long time, and the__version__
string was not updated in the last few releases. - The internal
Netrc
class in theftplib
module was deprecated in 3.4, and has now been removed. (Contributed by Matt Chaput in issue 6623.) - The concept of
.pyo
files has been removed. - The JoinableQueue class in the provisional asyncio module was deprecated in 3.4.4 and is now removed (issue 23464).
Porting to Python 3.5
This section lists previously described changes and other bugfixes that may require changes to your code.
Changes in the Python API
- PEP 475: System calls are now retried when interrupted by a signal instead
of raising
InterruptedError
if the Python signal handler does not raise an exception. - Before Python 3.5, a
datetime.time
object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See issue 13936 for full details. ssl.SSLSocket.send()
now raises eitherssl.SSLWantReadError
orssl.SSLWantWriteError
on a non-blocking socket if the operation would block. Previously, it would return 0. See issue 20951.- The
__name__
attribute of generator is now set from the function name, instead of being set from the code name. Usegen.gi_code.co_name
to retrieve the code name. Generators also have a new__qualname__
attribute, the qualified name, which is now used for the representation of a generator (repr(gen)
). See issue 21205. - The deprecated “strict” mode and argument of
HTMLParser
,HTMLParser.error()
, and theHTMLParserError
exception have been removed. (Contributed by Ezio Melotti in issue 15114.) The convert_charrefs argument ofHTMLParser
is nowTrue
by default. (Contributed by Berker Peksag in issue 21047.) - Although it is not formally part of the API, it is worth noting for porting purposes (ie: fixing tests) that error messages that were previously of the form “‘sometype’ does not support the buffer protocol” are now of the form “a bytes-like object is required, not ‘sometype’”. (Contributed by Ezio Melotti in issue 16518.)
- If the current directory is set to a directory that no longer exists then
FileNotFoundError
will no longer be raised and insteadfind_spec()
will returnNone
without cachingNone
insys.path_importer_cache
which is different than the typical case (issue 22834). - HTTP status code and messages from
http.client
andhttp.server
were refactored into a commonHTTPStatus
enum. The values inhttp.client
andhttp.server
remain available for backwards compatibility. (Contributed by Demian Brecht in issue 21793.) - When an import loader defines
exec_module()
it is now expected to also definecreate_module()
(raises aDeprecationWarning
now, will be an error in Python 3.6). If the loader inherits fromimportlib.abc.Loader
then there is nothing to do, else simply definecreate_module()
to returnNone
(issue 23014). re.split()
always ignored empty pattern matches, so the'x*'
pattern worked the same as'x+'
, and the'\b'
pattern never worked. Nowre.split()
raises a warning if the pattern could match an empty string. For compatibility use patterns that never match an empty string (e.g.'x+'
instead of'x*'
). Patterns that could only match an empty string (such as'\b'
) now raise an error.- The
Morsel
dict-like interface has been made self consistent: morsel comparison now takes thekey
andvalue
into account,copy()
now results in aMorsel
instance rather than adict
, andupdate()
will now raise an exception if any of the keys in the update dictionary are invalid. In addition, the undocumented LegalChars parameter ofset()
is deprecated and is now ignored. (issue 2211) - PEP 488 has removed
.pyo
files from Python and introduced the optionalopt-
tag in.pyc
file names. Theimportlib.util.cache_from_source()
has gained an optimization parameter to help control theopt-
tag. Because of this, the debug_override parameter of the function is now deprecated. .pyo files are also no longer supported as a file argument to the Python interpreter and thus serve no purpose when distributed on their own (i.e. sourcless code distribution). Due to the fact that the magic number for bytecode has changed in Python 3.5, all old .pyo files from previous versions of Python are invalid regardless of this PEP. - The
socket
module now exports the CAN_RAW_FD_FRAMES constant on linux 3.6 and greater. - The
pygettext.py
Tool now uses the standard +NNNN format for timezones in the POT-Creation-Date header. - The
smtplib
module now usessys.stderr
instead of previous module levelstderr
variable for debug output. If your (test) program depends on patching the module level variable to capture the debug output, you will need to update it to capture sys.stderr instead. - The
str.startswith()
andstr.endswith()
methods no longer returnTrue
when finding the empty string and the indexes are completely out of range. See issue 24284. - The
inspect.getdoc()
function now returns documentation strings inherited from base classes. Documentation strings no longer need to be duplicated if the inherited documentation is appropriate. To suppress an inherited string, an empty string must be specified (or the documentation may be filled in). This change affects the output of thepydoc
module and thehelp()
function. See issue 15582.
Changes in the C API
The undocumented
format
member of the (non-public)PyMemoryViewObject
structure has been removed.All extensions relying on the relevant parts in
memoryobject.h
must be rebuilt.The
PyMemAllocator
structure was renamed toPyMemAllocatorEx
and a newcalloc
field was added.Removed non-documented macro
PyObject_REPR
which leaked references. Use format character%R
inPyUnicode_FromFormat()
-like functions to format therepr()
of the object.Because the lack of the
__module__
attribute breaks pickling and introspection, a deprecation warning now is raised for builtin type without the__module__
attribute. Would be an AttributeError in future. (issue 20204)As part of PEP 492 implementation,
tp_reserved
slot ofPyTypeObject
was replaced with atp_as_async
slot. Refer to Coroutine Objects for new types, structures and functions.