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Python 3.6

Python 3.6 beta 1 was released on 12 Sep 2016, and a summary of the new features can be found here:

New Syntax Features


PEP 498

Literal String Formatting


PEP 515

Underscores in Numeric Literals


PEP 525

Asynchronous Generators

PEP 526

Syntax for Variable Annotations (provisional)


PEP 530

Asynchronous Comprehensions

New Built-in Features

PEP 468

Preserving the order of kwargs in a function

PEP 487

Simpler customization of class creation

PEP 520

Preserving Class Attribute Definition Order

Standard Library Changes

PEP 495

Local Time Disambiguation

PEP 506

Adding A Secrets Module To The Standard Library

PEP 519

Adding a file system path protocol

CPython Internals

PEP 509

Add a private version to dict

Won’t do

PEP 523

Adding a frame evaluation API to CPython

Linux/Window Changes

PEP 524

Make os.urandom() blocking on Linux (during system startup)

PEP 528

Change Windows console encoding to UTF-8

PEP 529

Change Windows filesystem encoding to UTF-8

Other Language Changes:

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 SyntaxWarning.

It is now possible to set a special method to None to indicate that the corresponding operation is not available. For example, if a class sets __iter__() to None , the class is not iterable.

Long sequences of repeated traceback lines are now abbreviated as [Previous line repeated {count} more times]

Import now raises the new exception ModuleNotFoundError when it cannot find a module. Code that currently checks for ImportError (in try-except) will still work.

Class methods relying on zero-argument super() will now work correctly when called from metaclass methods during class creation.

Changes to built-in modules:


Exhausted iterators of array.array will now stay exhausted even if the iterated array is extended.


The b2a_base64() function now accepts an optional newline keyword argument to control whether the newline character is appended to the return value



The new cmath.tau (τ) constant has been added

New constants: cmath.inf and cmath.nan to match math.inf and math.nan , and also cmath.infj and cmath.nanj to match the format used by complex repr


The new Collection abstract base class has been added to represent sized iterable container classes

The new Reversible abstract base class represents iterable classes that also provide the __reversed__() method.

The new AsyncGenerator abstract base class represents asynchronous generators.

The namedtuple() function now accepts an optional keyword argument module, which, when specified, is used for the __module__ attribute of the returned named tuple class.

The verbose and rename arguments for namedtuple() are now keyword-only.

Recursive collections.deque instances can now be pickled.


BLAKE2 hash functions were added to the module. blake2b() and blake2s() are always available and support the full feature set of BLAKE2.

The SHA-3 hash functions sha3_224(), sha3_256(), sha3_384(), sha3_512(), and SHAKE hash functions shake_128() and shake_256() were added.

The password-based key derivation function scrypt() is now available with OpenSSL 1.1.0 and newer.


json.load() and json.loads() now support binary input. Encoded JSON should be represented using either UTF-8, UTF-16, or UTF-32.


The new math.tau (τ) constant has been added



A new close() method allows explicitly closing a scandir() iterator. The scandir() iterator now supports the context manager protocol.

On Linux, os.urandom() now blocks until the system urandom entropy pool is initialized to increase the security.

The Linux getrandom() syscall (get random bytes) is now exposed as the new os.getrandom() function.


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’.

Match object groups can be accessed by __getitem__, which is equivalent to group(). So mo[‘name’] is now equivalent to‘name’).

Match objects now support index-like objects as group indices.


The ioctl() function now supports the SIO_LOOPBACK_FAST_PATH control code.

The getsockopt() constants SO_DOMAIN , SO_PROTOCOL, SO_PEERSEC , and SO_PASSSEC are now supported.

The setsockopt() now supports the setsockopt(level, optname, None, optlen: int) form.

The socket module now supports the address family AF_ALG to interface with Linux Kernel crypto API. ALG_, SOL_ALG and sendmsg_afalg() were added.

New Linux constants TCP_USER_TIMEOUT and TCP_CONGESTION were added.


ssl supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.

3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added.

SSLContext has better default configuration for options and ciphers.

SSL session can be copied from one client-side connection to another with the new SSLSession class. TLS session resumption can speed up the initial handshake, reduce latency and improve performance.

The new get_ciphers() method can be used to get a list of enabled ciphers in order of cipher priority.

All constants and flags have been converted to IntEnum and IntFlags.

Server and client-side specific TLS protocols for SSLContext were added.

Added SSLContext.post_handshake_auth to enable and ssl.SSLSocket.verify_client_post_handshake() to initiate TLS 1.3 post-handshake authentication.


now supports IEEE 754 half-precision floats via the ‘e’ format specifier.


The new getfilesystemencodeerrors() function returns the name of the error mode used to convert between Unicode filenames and bytes filenames.


The compress() and decompress() functions now accept keyword arguments