Python 3.6 beta 1 was released on 12 Sep 2016, and a summary of the new features can be found here: https://docs.python.org/3.6/whatsnew/3.6.html . Being in beta stage means we can provide feedback on any of the new features/changes if we like.

(See #1329 for Python 3.5 support, which is still pending.)

New syntax features:

• PEP 498 - Literal String Formatting : f-strings were implemented in 692d36d779192f32371f7f9daa845b566f26968d
• PEP 515 - Underscores in Numeric Literals; done in 6a445b60fad87c94a1d00ce3a043b881a1f7a5a4 ; see also #3831
• PEP 525 - Asynchronous Generators (provisional); see #6668
• PEP 526 - Syntax for Variable Annotations (provisional) for uPy: requires changes to parser, relevant for viper; see #6126
• 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 [not relevant to uPy core]
• PEP 519 - Adding a file system path protocol

CPython internals (not exposed at the Python level so not relevant to uPy):

• PEP 509 - Add a private version to dict
• PEP 523 - Adding a frame evaluation API to CPython

Linux/Windows changes:

• PEP 524 - Make os.urandom() blocking on Linux (during system startup)
• PEP 528 - Change Windows console encoding to UTF-8 (provisional)
• PEP 529 - Change Windows filesystem encoding to UTF-8 (provisional)

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 MicroPython built-in modules

• array - Exhausted iterators of array.array will now stay exhausted even if the iterated array is extended.
• asyncio (many, may need another ticket)
• binascii - The b2a_base64() function now accepts an optional newline keyword argument to control whether the newline character is appended to the return value.

• cmath
  • 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.
• collections
  • 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.
• hashlib
  • hashlib supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2.
  • 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 - json.load() and json.loads() now support binary input. Encoded JSON should be represented using either UTF-8, UTF-16, or UTF-32.
• math - The tau (τ) constant has been added to the math and cmath modules.
• os
  • See the summary of PEP 519 for details on how the os and os.path modules now support path-like objects.
  • 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.
• 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'.
  • Match object groups can be accessed by __getitem__, which is equivalent to group(). So mo['name'] is now equivalent to mo.group('name').
  • Match objects now support index-like objects as group indices.
• socket
  • 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
  • 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.

• struct - now supports IEEE 754 half-precision floats via the 'e' format specifier.
• sys - The new getfilesystemencodeerrors() function returns the name of the error mode used to convert between Unicode filenames and bytes filenames.
• zlib - The compress() and decompress() functions now accept keyword arguments.

(Changes to non-built-in modules will need to be documented elsewhere.)