Notable Features Introduced in Each Python Version

print statement replaced with a print() function

exec keyword replaced with an exec() function, which does not take a stream argument

dict.keys(), dict.items() and dict.values() now return “views” instead of lists

dict.iterkeys(), dict.iteritems(), and dict.itervalues() removed

map() now returns an iterator, stops when the shortest iterable is exhausted, and cannot take None as a function

filter() now returns an iterator

Python 2’s xrange() is Python 3’s range(); Python 2’s range() is no more

Python 2’s raw_input() is Python 3’s input(); Python 2’s input() is no more

Python 2’s long is Python 3’s int

• The repr() of a (long) integer no longer includes a trailing L

Python 2’s unichr is Python 3’s chr

zip() now returns an iterator

Order comparison operators now raise TypeError when given operands of different types

sorted() and list.sort() no longer accept the cmp parameter

cmp() and __cmp__() removed

Dividing two integers with / now returns a float

sys module:

• stdin, stdout, and stderr are now text streams

• maxint, exitfunc(), exc_clear(), exc_type, exc_value, and exc_traceback removed

itertools module:

• imap(), ifilter(), and izip() removed

• ifilterfalse() renamed to filterfalse()

• izip_longest() renamed to zip_longest()

math module: ceil() and floor() now return integers

array module:

• array.read() and array.write() removed

• c typecode removed

operator module: sequenceIncludes() and isCallable() removed

random module: jumpahead() API removed

os module: tmpnam(), tempnam(), and tmpfile() removed

string module: letters, lowercase, and uppercase removed

__builtin__ module renamed to builtins

Octal literals now use the prefix 0o instead of just 0

Python 2’s str is Python 3’s bytes; Python 2’s unicode is Python 3’s str

All string literals are now text/Unicode strs

The u prefix for text string literals is no longer supported (later reintroduced in Python 3.3)

Mixing byte strings and text strings now produces a TypeError

\uXXXX and \UXXXXXXXX escapes in raw string literals are now interpreted literally instead of being converted to Unicode characters

• As a consequence of this, the ur string prefix is no longer supported

basestring removed

The repr() of a string now longer escapes non-ASCII characters

The default Python source encoding is now UTF-8

Non-ASCII letters are now allowed in identifiers

StringIO and cStringIO removed; use io.StringIO and io.BytesIO instead

Function arguments and return values can now be annotated

Functions now have an __annotations__ attribute

Named parameters after *args or a bare * in a function signature are now keyword-only

Keyword arguments are allowed after the list of base classes in a class definition

New keyword: nonlocal

Extended iterable unpacking: Statements like a, b, *rest = some_sequence are now supported

Dictionary comprehensions added: {k: v for k, v in stuff}

Set literals and set comprehensions added: {1, 2} and {x for x in stuff}

New builtin functions: ascii() and next()

intern() moved to sys.intern()

Builtins apply(), buffer(), callable() (later reintroduced in Python 3.2), coerce(), execfile(), and file removed

reduce() moved to functools.reduce()

reload() moved to imp.reload()

dict.has_key() removed

round()’s rounding strategy and return type changed

True, False, and None are now reserved words

The syntax for using a metaclass has changed from:

class C:
    __metaclass__ = M
    ...

to:

class C(metaclass=M):
    ...

Special method __prepare__ on metaclasses added

Module-global __metaclass__ variable no longer supported

List comprehensions of the form [... for var in item1, item2, ...] must now be written [... for var in (item1, item2, ...)] instead.

The loop control variables of list comprehensions are no longer leaked into the surrounding scope

... (the ellipsis) can now be used as an expression anywhere, and it can no longer be spelled . . .

Tuple unpacking in function parameters no longer supported

Calling repr() via backticks no longer supported

<> removed

Trailing l or L on integer literals no longer supported

from module import * is no longer allowed inside functions

All module imports where the module name does not start with a period are now treated as absolute imports

Classic classes removed; all classes are now new-style

The following modules are removed: audiodev, Bastion/rexec, bsddb185, bsddb3, Canvas, cfmfile, cl, commands, compiler, dircache, dl, fpformat, gopherlib, htmllib, ihooks, imageop, imputil, linuxaudiodev, md5, mhlib, mimetools, MimeWriter, mimify, multifile, mutex, new, popen2, posixfile, pure, rfc822, sets, sgmllib, sha, sre, statvfs, stringold, sunaudio, sv, test.testall, thread, timing, toaiff, user, UserDict (moved to collections), UserList (moved to collections), and UserString (moved to collections)

All IRIX-specific, Mac-specific, and Solaris-specific modules removed

_winreg module renamed to winreg

ConfigParser module renamed to configparser

copy_reg module renamed to copyreg

Queue module renamed to queue

SocketServer module renamed to socketserver

cPickle module renamed to _pickle

cProfile module renamed to _profile

repr module renamed to reprlib

test.test_support module renamed to test.support

The modules anydbm, dbhash, dbm, dumbdm, gdbm, and whichdb have been combined into a new dbm module

HTMLParser module renamed to html.parser

htmlentitydefs module renamed to html.entities

httplib module renamed to http.client

The modules BaseHTTPServer, CGIHTTPServer, and SimpleHTTPServer have been combined into a new http.server module

Cookie module renamed to `http.cookies

cookielib module renamed to http.cookiejar

tkinter modules renamed as follows:

urllib2 module split into urllib.request and urllib.error modules

urlparse module renamed to urllib.parse

urllib module split into urllib.parse, urllib.request, and urllib.error modules

robotparser module renamed to urllib.robotparser

xmlrpclib module renamed to xmlrpc.client

The modules DocXMLRPCServer and SimpleXMLRPCServer have been combined into a new xmlrpc.server module

Exceptions must now inherit from BaseException

StandardError removed

Exceptions no longer behave like sequences; use the args attribute instead

except exc, var is now written except exc as var

The variable used to catch an exception is now deleted when the except block is left

raise Exception, args is now written raise Exception(args)

Raising an exception inside an except or finally block now causes implicit exception chaining

Explicit exception chaining can be done with raise SecondaryException() from primary_exception

__getslice__(), __setslice__(), and __delslice__() removed

Special method next() renamed to __next__()

__oct__() and __hex__() removed

Removed support for __members__ and __methods__

Function attributes of the form func_X renamed to __X__

Special method __nonzero__() renamed to __bool__()

super() can now be invoked without arguments inside an instance method

Multiple context managers can now be used in a single with statement

Directories & zip archives containing a __main__.py can now be executed by passing their path to the interpreter

Packages containing a __main__ submodule can now be executed with python -m and runpy

New bytes and bytearray method: maketrans()

The repr()s of floats are now shorter

New int method: bit_length()

The fields in strings formatted with str.format() can now omit numbering in order to be automatically numbered, as in 'Sir {} of {}'.format('Gallahad', 'Camelot')

The format specification mini-language now includes a thousands separator specifier

round(x, n) now returns an integer if x is an integer

New modules: importlib and tkinter.ttk

collections module:

• Counter and OrderedDict added

• namedtuple() now accepts a rename parameter

contextlib module: nested() is now deprecated

decimal module: Decimal.from_float() added

io module: SEEK_SET, SEEK_CUR, and SEEK_END added

itertools module:

• combinations_with_replacement() and compress() added

• count() now accepts a step parameter

json module: Decoders now accept an object_pairs_hook parameter

logging module: NullHandler added

re module: sub(), subn(), and split() now accept a flags parameter

string module: maketrans() is now deprecated

New modules: argparse, concurrent.futures, html, and sysconfig

.pyc files are now stored in __pycache__/ directories

Modules now have a __cached__ attribute

New str method: format_map()

The str() of a float or complex is now the same as its repr()

New range methods: index() and count()

callable() function from Python 2 restored

ResourceWarning warning type added

abc module: abstractclassmethod() and abstractstaticmethod() added

ast module: literal_eval() now supports set & bytes literals

collections module:

• Counter.subtract() added

• OrderedDict.move_to_end() added

• deque.count() and deque.reverse() added

compileall command-line interface: -i and -b options added

configparser module:

• ConfigParser class replaced with SafeConfigParser, which is now customizable

• New API added based on the mapping protocol

contextlib module:

• ContextDecorator added

• nested() removed

csv module:

• unix_dialect dialect (dialect name "unix") added

• DictWriter.writeheader() added

datetime module:

• timezone added

• timedelta instances can now be multiplied by floats and divided by floats & ints

• date.strftime() now supports years from 1000 through 9999

decimal module:

• The Decimal constructor now accepts floats

• Decimal instances can now be compared with float and fractions.Fraction instances

• Context.clamp added

email.parser module: BytesFeedParser, BytesParser, message_from_bytes() and message_from_binary_file() added

email.generator module: BytesGenerator added

fractions module: The Fraction constructor now accepts floats and decimal.Decimals

functools module: cmp_to_key(), lru_cache(), and total_ordering() added

gzip module: compress() and decompress() added

hashlib module: algorithms_available and algorithms_guaranteed added

Various ABCs added to importlib.abc

inspect module: getgeneratorstate() and getattr_static() added

io module: BytesIO.getbuffer() added

itertools module: accumulate() added

json module: The indent parameter to dumps() etc. can now be a string

logging module:

• basicConfig() now accepts a style parameter

• If a logging event occurs before any explicit configuration is set up, a default configuration (available in lastResort) is now enabled

• Python callables returning booleans can now be used as filters

logging.config module: dictConfig() added

math module: isfinite(), expm1(), erf(), erfc(), gamma(), and lgamma() added

os module: fsencode(), fsdecode(), supports_bytes_environ, getenvb(), and environb added

shutil module:

• copytree() now accepts ignore_dangling_symlinks and copy_function parameters

• make_archive(), unpack_archive(), etc. added

site module: getsitepackage(), getuserbase(), and getusersitepackages() added

smtplib module: SMTP.send_message() added

ssl module:

• SSLContext and match_hostname() added

• Server Name Indication (SNI) is now supported when linked against recent versions of OpenSSL

string module: maketrans() removed

sys module: hash_info added

tarfile module: TarFile.add() now accepts a filter parameter, and the exclude parameter is now deprecated

tempfile module: TemporaryDirectory added

threading module: Barrier added

unicodedata updated to Unicode 6.0.0

urllib.parse module: urlparse() now supports IPv6 addresses

New modules: faulthandler, ipaddress, lzma, unittest.mock, and venv

Support for implicit namespace packages (directories without an __init__.py) added

All Unicode codepoints, from U+0000 to U+10FFFF, are now always supported; there is no longer a distinction between “narrow” and “wide” builds

Multiple exception types have been merged into OSError, which now has various subclasses for common error conditions

Delegating to a subgenerator/subiterator with yield from is now possible

Chained exception context can be suppressed with raise e from None

The u"unicode" syntax for Unicode strings from Python 2 is now supported again

Functions & classes now have a __qualname__ attribute

inspect module: signature(), Signature, Parameter, and BoundArguments added

sys module: implementation added

types module: SimpleNamespace added

importlib module: Various classes & functions added

Modules now have a __loader__ attribute

"\N{...}" can now take name aliases

unicodedata updated to UCD 6.1.0

New list and bytearray methods: copy() and clear()

Raw bytes literals can now be written rb"..." in addition to br"..."

open() now accepts an opener parameter

print() now accepts a flush parameter

Hash randomization with hash() is now enabled by default

New str method: casefold()

abc:

• It is now possible to combine abstractmethod with property, classmethod, or staticmethod

• abstractproperty, abstractclassmethod, and abstractstaticmethod are now deprecated

• ABCMeta.register() can now be used as a class decorator

array module: long long type now supported

base64 module: Decoding functions now accept ASCII-only strs

binascii module: The a2b_* functions now accept ASCII-only strs

bz2 module:

• open() added

• BZ2File() now accepts arbitrary file-like objects and implements most of the io.BufferedIOBase API

collections module:

• ChainMap added

• ABCs moved to collections.abc; aliases are still present in collections itself, but importing them is deprecated

• Counter now supports +, -, +=, -=, |=, and &=

contextlib module: ExitStack added

datetime module: New datetime methods: timestamp(), strftime(), and astimezone()

email module: Policy framework added

email.parser module: BytesHeaderParser added

email.utils module: format_datetime(), parsedate_to_datetime(), and localtime() added

functools module: lru_cache() now accepts a typed parameter

hmac module: compare_digest() added

http.client module: HTTPResponse.readinto() added

html.parser module: HTMLParser can now parse broken markup without errors

html.entities: html5 added

inspect module: getclosurevars() and getgeneratorlocals() added

io module:

• x mode added to open() function

• The TextIOWrapper constructor now accepts a write_through parameter

itertools module: accumulate() now accepts a func parameter

logging module: basicConfig() now accepts a handlers parameter

math module: log2() added

multiprocessing module:

• The Process constructor now accepts a daemon parameter

• Process.sentinel added

multiprocessing.connection module: wait() added

multiprocessing.pool module: New Pool methods starmap() and starmap_async() added

os module:

• fwalk(), pipe2(), sendfile(), getpriority(), setpriority(), replace(), get_terminal_size(), getxattr(), listxattr(), removexattr(), setxatter(), sync(), and others added

• Various functions now accept dir_fd and/or follow_symlinks parameters

• Various functions can now take file descriptors as path arguments

• stat(), fstat(), lstat(), and utime() now support timestamps with nanosecond precision

re module: str regular expressions now support \uXXXX and \UXXXXXXXX escapes

pipes.quote() moved to shlex

shutil module:

• disk_usage(), chown(), and get_terminal_size() added

• Several functions now accept a symlink parameter

stat module: filemode() added

struct module: size_t and ssize_t now supported

subprocess:

• Command strings can now be bytes on POSIX

• DEVNULL added

sys module: thread_info added

textwrap module: indent() added

time module: get_clock_info(), monotonic(), perf_counter(), process_time(), clock_getres(), clock_gettime(), clock_settime(), and CLOCK_* constants added

types module: MappingProxyType, new_class(), and prepare_class() added

urllib.request module: The Request constructor now accepts a method parameter

array module: The u format is now deprecated

New modules: asyncio, ensurepip, enum, pathlib, selectors, statistics, and tracemalloc

codecs module: encode() and decode() are now documented

unicodedata updated to UCD 6.3

min() and max() now accept a default parameter

New special method: __length_hint__()

abc module: ABC and get_cache_token() added

argparse module: FileType now accepts encoding and errors parameters

base64 module:

• Encoding & decoding functions now accept any bytes-like object

• a85encode(), a85decode(), b85encode(), and b85decode() added

contextlib module: suppress() and redirect_stdout() added

doctest command-line interface: -o and -f options added

email module:

• as_string() now accepts a policy argument

• as_bytes() method added

• EmailMessage and MIMEPart added as part of new API

• contextmanager submodule added

filecmp module: clear_cache() and DEFAULT_IGNORES added

functools module: partialmethod() and singledispatch() added

glob module: escape() added

hashlib module: pbkdf2_hmac() added

html module: unescape() added

html.parser module: HTMLParser constructor now accepts a convert_charrefs parameter, and the strict argument is now deprecated

http.server command-line interface: --bind option added

imp.reload() moved to importlib

importlib module: InspectLoader.source_to_code() added

importlib.util module: MAGIC_NUMBER, cache_from_source(), source_from_cache(), and decode_source() added

importlib.machinery module: ExtensionFileLoader.get_filename() added

runpy and python -m can now be used with namespace packages

inspect module:

• Command-line interface added

• unwrap() added

ipaddress module: is_global property added

json module: dumps() etc. will now automatically set separators to (",", ": ") when indent is non-None

multiprocessing module:

• Start methods spawn and forkserver added

• Contexts added

• get_all_start_methods(), get_start_method(), set_start_method(), and get_context() added

operator module: length_hint() added

os module:

• cpu_count() added

• open() now supports the O_PATH and O_TMPFILE flags

pdb module: print command removed

pickle module: Protocol 4 added

plistlib module: load(), dump(), loads(), and dumps() added

pprint module: PrettyPrinter, pformat(), and pprint() now accept a compact parameter

re module: fullmatch() and regex.fullmatch() added

resource module: prlimit() added

shutil module: copyfile() now raises a SameFileError when the source and destination are the same file

ssl module:

• create_default_context() and get_default_verify_paths() added

• New SSLContext methods: cert_store_stats(), get_ca_certs(), and load_default_certs()

stat module: S_IFDOOR, S_IFPORT, and S_IFWHT added

struct module: iter_unpack() and Struct.iter_unpack() added

subprocess module:

• check_output() now accepts an input parameter

sys module: getallocatedblocks() and __interactivehook__ added

tarfile module: Command-line interface added

textwrap module:

• The TextWrapper constructor now accepts max_lines and placeholder parameters

• shorten() added

threading module: main_thread() added

traceback module: clear_frames() added

types module: DynamicClassAttribute() added

urllib.request module:

• data: URLs now supported

• Request objects are now reusable

urllib.error module: HTTPError.headers added

venv module: The EnvBuilder constructor and create() now accept a with_pip parameter

importlib module: A number of methods & functions are deprecated

The imp module is now deprecated and will be removed in Python 3.12

The formatter module is now deprecated and will be removed in Python 3.10

The U mode of various “open” functions is now deprecated and will be removed in Python 3.11

Coroutine functions (async def), awaitable objects (await and __await__()), asynchronous iteration (async for, __aiter__(), and __anext__()), and asynchronous context managers (async with, __aenter__(), and __aexit__()) added

@ operator (with __matmul__() etc. special methods) for matrix multiplication added

Multiple * and/or ** unpackings can now be used in a single function call

Tuple, list, set, & dictionary displays may now contain * or ** unpackings (as appropriate)

Percent-formatting of bytes and bytearray objects with % added

New modules: typing and zipapp

System calls are now retried when interrupted by a signal

from __future__ import generator_stop added to cause StopIteration exceptions raised inside generators to be transformed into RuntimeExceptions, which becomes the default in Python 3.7

• Without the __future__ import, such exceptions generate PendingDeprecationWarnings.

RecursionError exception type (a subclass of RuntimeError) added

.pyo files eliminated; optimized bytecode is now stored in .pyc files with opt- tags in their name

"namereplace" error handler added

Various additions & improvements to the asyncio module

cmath module: isclose() added

collections module:

• New deque methods: index(), insert(), and copy()

• deque now supports + and *

collections.abc module: Generator, Awaitable, Coroutine, AsyncIterator, and AsyncIterable added

configparser module: ConfigParser can now take a dictionary of converters, and subclasses can define additional converters as methods

contextlib module: redirect_stderr() added

enum module: The Enum callable now accepts a start parameter

glob module: glob() and iglob()` now support the ``** pattern

http module: HTTPStatus added

importlib.util module: module_from_spec() added

inspect module:

• BoundArguments.apply_defaults() added

• Signature.from_callable() added

• signature() now accepts a follow_wrapped parameter

• iscoroutine(), iscoroutinefunction(), isawaitable(), getcoroutinelocals(), and getcoroutinestate() added

io module: new BufferedIOBase method: readinto1()

ipaddress module:

• The IPv4Network and IPv6Network constructors now accept an (address, netmask) argument

• New IPv4Network and IPv6Network attribute: reverse_pointer

json module: JSON decoding errors now raise JSONDecodeError

json.tool command-line interface: The input order of keys is now preserved on output; the --sort-keys option will sort the keys instead

linecache module: lazycache() added

locale module: delocalize() added

logging module: Logging methods now accept exception instances as exc_info arguments

math module: isclose(), gcd(), inf, and nan added

fractions module: gcd() is now deprecated and will be removed in Python 3.9

operator module: matmul() and imatmul() added

os module: scandir() added

os.path module: commonpath() added

pathlib module:

• New Path methods: samefile(), expanduser(), write_text(), read_text(), write_bytes(), and read_bytes()

• Class method Path.home() added

• Path.mkdir() now accepts an exist_ok parameter

readline module: append_history_file() added

selectors module: DevpollSelector added

shutil module: move() now accepts a copy_function argument

signal module: SIG* constants have been converted to enums

socket module: socket.sendfile() added

ssl module: SSLObject added

subprocess: run() added

sys module: set_coroutine_wrapper(), get_coroutine_wrapper(), and is_finalizing() added

time module: monotonic() is now always available

timeit command-line interface: --unit option added

traceback module: TracebackException, StackSummary, FrameSummary, walk_stack(), and walk_tb() added

types module: CoroutineType and coroutine() added

unicodedata updated to Unicode 8.0.0

unittest command-line interface: --locals option added

unittest.mock module: Mock.assert_not_called() added

urllib.request module: HTTPPasswordMgrWithPriorAuth added

platform module: dist() and linux_distribution() are now deprecated

html.parser module: The convert_charrefs parameter to the HTMLParser constructor now defaults to True

Formatted string literals (“f-strings”)

Variables can now be annotated by following the name of the variable with a colon and the annotation

Underscores can now be used in numeric literals

await and yield can now be used in the same function, thereby enabling asynchronous generators

async for can now be used in list, set, & dict comprehensions and in generator expressions

await expressions can now be used in any comprehension

Special methods __init_subclass__() and __set_name__() added

os.PathLike, the __fspath__() method, and os.fspath() added

• Relevant file functions now accept os.PathLike objects

ModuleNotFoundError exception type (a subclass of ImportError) added

datetime module:

• fold attribute added to datetime and time for denoting the second instance of a time duplicated due to DST

• The strftime() method of date and datetime now supports %G, %u, and %V

• datetime.astimezone() can now be called on naïve instances

The file system and console encodings on Windows are now both UTF-8

A class’s __dict__ now preserves the order in which the attributes were defined

**kwargs now preserves insertion order

dicts are now implemented in such a way that they preserve insertion order

New module: secrets

Various additions & improvements to the asyncio module

cmath module: tau, inf, nan, infj, and nanj added

collections.abc: Collection, Reversible, and AsyncGenerator added

enum module: auto, Flag, and IntFlag added

json module: load() and loads() now support binary input in UTF-8, UTF-16, and UTF-32

math module: tau added

random module: choices() added

re module:

• Modifier spans (e.g., as in '(?i)g(?-i:v)r') are now supported in regular expressions

• Match objects can now be indexed to access groups

statistics module: harmonic_mean() added

The smtpd module is now deprecated and will be removed in Python 3.12

subprocess module:

• encoding and errors arguments added to Popen and the wrappers around it

• The args parameter to Popen and the wrappers around it can now be a path-like object or sequence of path-like objects on POSIX systems

time module: The tm_gmtoff and tm_zone attributes of struct_time are now available on all platforms

typing module:

• Generic type aliases like Dict[str, Tuple[S, T]] are now supported

• TYPE_CHECKING added

• ClassVar added

• NewType() added

• NamedTuple now supports variable annotation syntax

unittest.mock module: New Mock methods assert_called() and assert_called_once() added

venv command-line interface: --prompt option added

Using async or await as a name will now generate a DeprecationWarning

StopIteration exceptions raised inside generators now generate DeprecationWarnings

Invalid escape sequences now generate a DeprecationWarning

The asynchat and asyncore modules are now deprecated and will be removed in Python 3.12

The pyvenv script for creating venvs is now deprecated and will be removed in Python 3.8

unicodedata updated to Unicode 9.0.0

from __future__ import annotations added to enable postponed evaluation of annotations

dicts are now guaranteed to preserve insertion order

async and await are now reserved keywords

New modules: contextvars, dataclasses, importlib.resources

New builtin function: breakpoint()

The interpreter now coerces ASCII locales to UTF-8 under certain circumstances on non-Windows OSes

__aiter__() methods can no longer be asynchronous

__getattr__() and __dir__() can now be defined on modules

time module: variants of the timer functions added that return a number of nanoseconds as an integer

Special methods __class_getitem__() and __mro_entries__() added

Python Development Mode added

New str, bytes, and bytearray method: isascii()

argparse module: ArgumentParser.parser_intermixed_args() added

Various additions & improvements to the asyncio module

• asyncio.run() added

collections module: defaults argument added to namedtuple()

contextlib module: nullcontext(), asynccontextmanager(), and AsyncExitStack added

datetime module:

• datetime.fromisoformat() added

• The "%z" format of the strptime() methods now accepts timezone offsets containing colons as well as a timezone specifier of “Z”.

enum module: Support for the _ignore_ class property added to Enum

functools module: singledispatch() now recognizes type annotations

http.server command-line interface: --directory option added

ipaddress module: subnet_of() and supernet_of() methods added to IPv4Network and IPv6Network

locale module: format() is now deprecated and will be removed in Python 3.12

math module: remainder() added

pathlib module: Path.is_mount() added

queue module: SimpleQueue added

subprocess module:

• capture_output argument added to run()

• text argument added to run() and the Popen constructor

Removed the fpectl module

StopIteration exceptions raised inside coroutines and generators are now transformed into RuntimeExceptions

unicodedata updated to Unicode 11

Assignment expressions: := (the “walrus operator”) can now be used to assign a value to a variable in the middle of an expression, e.g.:

if m := re.search(r'\d+', s):
    x = int(m.group())

Function parameters can now be made positional-only by placing a / after them in the argument list

One can now write f"{var=}" to get f"{var}={repr(var)}"

continue is now allowed in finally: clauses

New int, bool, and fractions.Fraction method: as_integer_ratio()

\N{name} escapes are now allowed in regular expressions

dicts and dictviews can now be passed to reversed()

Generalized iterable unpacking in yield and return statements no longer requires parentheses; e.g., one can now write return foo, *bar instead of having to do return (foo, *bar)

Missing commas between tuples in a list now generate a SyntaxWarning with a suggestion as to what went wrong

For integer arguments, the three-argument form of pow() can now take a negative exponent when the base is coprime to the modulus, in which case the modular multiplicative inverse (or a power thereof) is calculated

New modules: importlib.metadata and multiprocessing.shared_memory

Running python -m asyncio now starts an async REPL

asyncio module:

• CancelledError now inherits directly from BaseException instead of Exception

• coroutine() is now deprecated and will be removed in Python 3.11

• Passing a loop parameter is now deprecated for most of asyncio’s high-level API; it will be removed entirely in Python 3.10

• Explicitly passing coroutines to wait() is now deprecated

datetime module: New date and datetime method: fromisocalendar()

functools module: cached_property() and singledispatchmethod() added

io module: open_code() (the verified open hook) added

itertools module: accumulate() now accepts an initial parameter

json.tool command-line interface: --json-lines option added

math module:

• comb() added

• dist() added

• hypot() can now take multiple arguments

• isqrt() added

• perm() added

• prod() added

pathlib module:

• Path.link_to() added

• Path.rename() and Path.replace() now return the new path

• Path.unlink() now accepts a missing_ok argument

pickle module: Protocol 5 (with support for out-of-band buffers) added

platform module: dist() and linux_distribution() removed

shlex module: join() added

statistics module: NormalDist, fmean(), geometric_mean(), multimode(), and quantiles() added

subprocess module: The args parameter to Popen and the wrappers around it can now be a path-like object or sequence of path-like objects on Windows systems in addition to POSIX

sys module:

• audit() and addaudithook() (for audit hooks) added

• pycache_prefix added

• unraisablehook() and __unraisablehook__ added

typing module: TypedDict, Literal, Final, final(), Protocol, SupportsIndex, get_origin(), and get_args() added

unicodedata module:

• Updated to Unicode 12.1.0

• is_normalized() added

unittest.mock module:

• AsyncMock added

• call objects now have args and kwargs properties

zipfile module: Path added

Removed:

• macpath module (deprecated since Python 3.7)

• time.clock() (deprecated since Python 3.3)

• the pyvenv script for creating venvs (Use pythonX.Y -m venv instead)

• sys.set_coroutine_wrapper() and sys.get_coroutine_wrapper() (deprecated since Python 3.7)

Using is or is not with strings, numbers, and certain other literals now produces a SyntaxWarning

dicts can now be merged & updated using the | and |= operators

Any valid expression can now be used as a decorator

New str, bytes, and bytearray methods: removeprefix() and removesuffix()

Built-in collection types like list and dict can now be used as generic types; e.g., List[str] can now be written list[str]

• This also applies to collections ABCs; e.g., typing.Sequence[str] can now be written collections.abc.Sequence[str].

• Importing the old List, Sequence, etc. types from typing is now deprecated but does not generate DeprecationWarningss at this time. The deprecated names will be removed from typing in the first Python release five years after 3.9.

New modules: graphlib and zoneinfo

asyncio module: to_thread() added

functools module: cache() added

importlib.resources module: files() added (introduced in importlib-resources v1.1.0)

Aligned importlib.metadata with importlib-metadata v1.6.1

ipaddress module now supports IPv6 scoped addresses

math module:

• gcd() can now take multiple arguments

• lcm(), nextafter(), and ulp() added

pathlib module:

• Path.readlink() added

• PurePath.is_relative_to() added

• PurePath.with_stem() added

random module: randbytes() added

typing module: Annotated added

The binhex, parser, and symbol modules are now deprecated

Using NotImplemented in a boolean context is now deprecated and will produce a TypeError in a future version of Python

Removed:

• fractions.gcd() (deprecated since Python 3.5)

• encoding parameter of json.loads() (deprecated & ignored since Python 3.1)

• asyncio.Task.current_task() and asyncio.Task.all_tasks() (deprecated since Python 3.7); use asyncio.current_task() and asyncio.all_tasks() instead

with (await asyncio.lock): and with (yield from asyncio.lock): statements are no longer supported; use async with lock instead. Likewise for asyncio.Condition and asyncio.Semaphore.

lib2to3 now emits a PendingDeprecationWarning and will be removed in Python 3.13

unicodedata updated to Unicode 13.0.0

Pattern matching!

match status:
    case 400:
        return "Bad request"
    case 401 | 403 | 404:
        return "Not allowed"
    case _:
        return "Something's wrong with the Internet"

Context managers in with statements can now be enclosed in parentheses, e.g.:

with (CtxManager1() as example,
      CtxManager2()):

Assignment expressions can now be used unparenthesized within set literals, set comprehensions, and sequence indexes (but not slices)

Numeric literals immediately followed by keywords (e.g., 0in x) now generate a deprecation warning. Future Python versions will change this to a syntax warning and then a syntax error.

Common syntax errors now have better error messages

AttributeError and NameError error messages now include suggestions as to what you might have meant

Union[X, Y] can now be written X | Y

Dictionary views returned by dict.keys(), dict.values(), and dict.items() now have mapping attributes wrapping the original dict

The second argument of isinstance() and issubclass() can now be a Union

New int method: bit_count()

open() and friends can now be passed encoding="locale" in order to explicitly use the current locale’s encoding

zip() now has a strict parameter for requiring that all input iterables have the same length

New builtin functions: aiter() and anext()

EncodingWarning warning type added

The loop parameter (deprecated in Python 3.8) is now removed from most of asyncio’s high-level API

base64 module: b32hexencode() and b32hexdecode() added

bisect module: The functions now accept a key argument

codecs module: unregister() added

Collections ABCs can no longer be imported from collections; import them from collections.abc instead

collections module: Counter.total() added

contextlib: aclosing() added

dataclasses:

• The dataclass decorator now accepts a slots argument

• Fields can now be made keyword-only

distutils is now deprecated and will be removed in Python 3.12

glob module: glob() and iglob() now accept root_dir and dir_fd arguments

Aligned importlib.metadata with importlib-metadata v4.6

• entry_points() and package_distributions() added

inspect module: get_annotations() added

io module: text_encoding() added

itertools module: pairwise() added

os.path.realpath() now has a strict parameter for erroring when a path doesn’t exist or a symlink loop is encountered

pathlib module:

• Slice and negative indexing support added to Path.parents

• Path.hardlink_to() added, superseding Path.link_to(), which is now deprecated and will be removed in Python 3.12

• Path.stat() and Path.chmod() now have a follow_symlinks argument

platform module: freedesktop_os_release() added

statistics module: covariance(), correlation(), and linear_regression() added

sys module: orig_argv and stdlib_module_names added

traceback module: format_exception(), format_exception_only(), and print_exception() can now take just an exception argument as a positional-only parameter

types module: EllipsisType, NoneType, and NotImplementedType added

typing module: Concatenate, ParamSpec, TypeAlias, TypeGuard, and is_typeddict() added

Removed the formatter and parser modules (deprecated in Python 3.4 and 3.9, respectively)

Exception groups

• ExceptionGroup and BaseExceptionGroup exception types added

• try: ... except* ...: ... syntax (note asterisk) for matching exception groups

Traceback messages now highlight the exact expression that caused the error

Starred expressions can now be used in for statements (e.g., for x in *lst1, *lst2:)

• This was enabled by the grammar rewrite in Python 3.9 but was not noticed or documented until 3.11.

Octal escapes in string & bytes literals with values greater than 0o377 (e.g., \477) now generate a DeprecationWarning

The various “open” functions no longer accept the U mode

New object method: __getstate__()

New BaseException method: add_note()

Chaining @classmethod decorators and using them to wrap other decorators (such as @property) is now deprecated and will be removed in Python 3.13

Format specification mini-language: A z option can now be used with floating-point types in order to coerce negative zero to “regular” zero after rounding.

New modules: tomllib and wsgiref.types

asyncio module:

• @coroutine (deprecated since 3.8) and asyncio.coroutines.CoroWrapper removed

• Barrier, Runner, TaskGroup, and timeout() added

binascii module: a2b_hqx(), b2a_hqx(), rlecode_hqx(), and rledecode_hqx() removed

binhex module removed

contextlib module: chdir() added

datetime module:

• UTC added

• The fromisoformat() methods now accept most ISO 8601 strings

enum module:

• EnumCheck, FlagBoundary, ReprEnum, StrEnum, @global_enum(), @member(), @nonmember(), @property, show_flag_values(), and @verify added

• EnumMeta renamed to EnumType; the old name is currently as an alias

functools module: singledispatch now supports union types

hashlib module: file_digest() added

inspect module:

• getmembers_static() and ismethodwrapper() added

• formatargspec() and getargspec() removed

• Frame-related functions now return objects instead of tuples (though the new objects are backwards-compatible with the tuple interface)

locale module:

• getdefaultlocale() is now deprecated and will be removed in Python 3.13

• getencoding() added

logging module:

• getLevelNamesMapping() added

• createSocket() method added to logging.handlers.SysLogHandler

math module: cbrt() and exp2() added

operator module: call() added

pathlib module: The glob() and rglob() methods now return only directories if given a pattern ending with the pathname separator

re module:

• (?>...), *+, ++, ?+, and {m,n}+ can now be used in regular expressions

• NOFLAG added

string module: get_identifiers() and is_valid() methods added to string.Template

sys module: exception() added

typing module:

• LiteralString, Never, Self, TypeVarTuple, Unpack, assert_never(), assert_type(), clear_overloads(), get_overloads(), @dataclass_transform, and reveal_type() added

• Text is now deprecated

• Individual fields in a TypedDict may now be annotated as Required or NotRequired

• The keyword-argument syntax for constructing TypedDict types is now deprecated and will be removed in Python 3.13

unicodedata updated to Unicode 14.0.0

zipfile module:

• metadata_encoding argument added to ZipFile constructor

• ZipFile.mkdir() added

• stem, suffix, and suffixes attributes added to zipfile.Path

The following modules are now deprecated and are planned to be removed in Python 3.13: aifc, audioop, cgi, cgitb, chunk, crypt, imghdr, mailcap, msilib, nis, nntplib, ossaudiodev, pipes, sndhdr, spwd, sunau, telnetlib, uu, and xdrlib

New syntax for type-annotating generic classes, generic functions, and type aliases:

• Generic class:

  • Old syntax:

    from typing import Generic, TypeVar
    
    T_str = TypeVar("T_str", covariant=True, bound=str)
    
    class ClassA(Generic[T_str]):
        def method1(self) -> T_str:
            ...
    

  • New syntax:

    # No Generic or TypeVar
    
    class ClassA[T: str]:
        def method1(self) -> T:
            ...
    

• Generic function:

  • Old syntax:

    from typing import TypeVar
    
    T = TypeVar("T")
    
    def func(a: T, b: T) -> T:
        ...
    

  • New syntax:

    # No TypeVar
    
    def func[T](a: T, b: T) -> T:
        ...
    

• Type alias:

  • Old syntax:

    from typing import TypeAlias
    
    IntOrStr: TypeAlias = int | str
    

  • New syntax:

    type IntOrStr = int | str
    

• Generic type alias:

  • Old syntax:

    from typing import TypeAlias
    
    T = TypeVar("T")
    
    ListOrSet: TypeAlias = list[T] | set[T]
    

  • New syntax:

    # No TypeVar
    
    type ListOrSet[T] = list[T] | set[T]
    

• Variadic type alias:

  • Old syntax:

    from typing import TypeAlias, TypeVarTuple
    
    Ts = TypeVarTuple("Ts")
    
    IntEtc: TypeAlias = tuple[int, *Ts]
    

  • New syntax:

    type IntEtc[*Ts] = tuple[int, *Ts]
    

• Type alias with a parameter spec:

  • Old syntax:

    from collections.abc import Callable
    from typing import ParamSpec, TypeAlias
    
    P = ParamSpec("P")
    
    IntMaker: TypeAlias = Callable[P, int]
    

  • New syntax:

    from collections.abc import Callable
    
    type IntMaker[**P] = Callable[P, int]
    

Types of individual fields in a **kwargs function parameter can now be annotated with typing.Unpack applied to a TypedDict, like so:

from typing import TypedDict, Unpack

class Movie(TypedDict):
    name: str
    year: int

def foo(**kwargs: Unpack[Movie]):
    # kwargs["name"] must be passed a `str`, and kwargs["year"] must be
    # passed an `int`.
    ...

{..} placeholders inside f-strings may now contain any valid Python expression

• Quotes from the enclosing string may now be reused:

  >>> songs = ['Take me back to Eden', 'Alkaline', 'Ascensionism']
  >>> f"This is the playlist: {", ".join(songs)}"
  'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'
  

• Expressions inside f-strings may now span multiple lines and contain inline comments.

• Expressions inside f-strings may now contain backslashes.

The buffer protocol is now accessible in Python code:

• Special methods __buffer__() and __release_buffer__() added

• collections.abc module: Buffer added

• inspect module: BufferFlags added

Source code containing NUL bytes now results in a SyntaxError

Invalid escape sequences now generate a SyntaxWarning

Octal escapes in string & bytes literals with values greater than 0o377 (e.g., \477) now generate a SyntaxWarning

Applying ~ (bitwise inversion) to a bool is now deprecated and will become an error in Python 3.14.

Removed modules:

• asynchat (deprecated in Python 3.6)

• asyncore (deprecated in Python 3.6)

• distutils (deprecated in Python 3.10)

• imp (deprecated in Python 3.4)

• smtpd (deprecated in Python 3.6)

array module: The array class is now subscriptable and thus properly generic

ast module: Accessing or using any of Bytes, Ellipsis, NameConstant, Num, and Str now generates a DeprecationWarning. They are planned to be removed in Python 3.14.

asyncio module:

• as_completed() and wait() now accept generators yielding tasks

• create_eager_task_factory() and eager_task_factory() added

• run() now takes an optional loop_factory parameter

calendar module: Day and Month added

collections.abc module: ByteString is now deprecated and will be removed in Python 3.14

configparser module: ConfigParser.readfp(), ParsingError.filename, and SafeConfigParser removed (deprecated in Python 3.2)

datetime module: datetime.utcnow() and datetime.utctimestamp() are now deprecated

fraction module: Fraction instances now support float-style formatting

importlib.abc module: ResourceReader, Traversable, and TraversableResources are now deprecated and will be removed in Python 3.14

importlib.resources: as_file() now supports resource directories

inspect module: getasyncgenlocals(), getasyncgenstate(), and markcoroutinefunction() added

itertools: batched() added

locale module: format() removed (deprecated in Python 3.7)

math module:

• nextafter() now takes an optional steps parameter

• sumprod() added

os module:

• DirEntry.is_junction() added

• listdrives(), listmounts(), listvolumes(), pidfd_open(), setns(), and unshare() added

• Calling fork() or forkpty() in a multithreaded program now generates a DeprecationWarning

os.path module: isjunction() and splitroot() added

pathlib module:

• Path classes can now be subclassed

• PurePath.with_segments() added

• Path.is_junction() and Path.walk() added

• PurePath.match(), Path.glob(), and Path.rglob() now take an optional case_sensitive parameter

• PurePath.relative_to() now takes an optional walk_up parameter

pkgutil module: find_loader() and get_loader() are now deprecated and will be removed in Python 3.14

random module:

• binomialvariate() added

• The lambd argument to expovariate() now defaults to 1.0

shutil module:

• rmtree() now takes an optional onexc parameter. The onerror parameter is deprecated and will be removed in Python 3.14.

• unpack_archive() now takes an optional filter parameter for limiting what gets extracted from tar archives

sqlite3 module:

• Command-line interface added

• connect() now takes an optional autocommit parameter

• Connection.autocommit, Connection.getconfig(), and Connection.setconfig() added

• The default adapters and converters are now deprecated

ssl module: match_hostname() and wrap_socket() removed (deprecated in Python 3.7)

statistics module: correlation() now takes an optional method parameter that can be either "linear" (the default) or "ranked"

sys module:

• activate_stack_trampoline(), deactivate_stack_trampoline(), is_stack_trampoline_active(), and last_exc added

• last_type, last_value, and last_traceback are now deprecated

sys.monitoring added

tarfile module: The TarFile.extract() and TarFile.extractall() methods now take an optional filter parameter for limiting what gets extracted in order to avoid security issues. Calling one of these methods without setting a filter will generate a DeprecationWarning until Python 3.14, in which the default filter will become "data".

tempfile module:

• NamedTemporaryFile now takes an optional delete_on_close parameter

• mkdtemp() now always returns an absolute path

types module: get_original_bases() added

typing module:

• override added

• dataclass_transform() now takes an optional frozen_default parameter

• Hashable and Sized are now deprecated

unicodedata updated to Unicode 15.0.0

unittest command-line interface: --durations option added

uuid module: Command-line interface added

venv module: setuptools is no longer automatically installed in virtual environments