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QUERY · ISSUE

Discussion of Python 3.6 support

openby dpgeorgeopened 2016-09-13updated 2022-01-22
rfc

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.)

CANDIDATE · ISSUE

Discussion of Python 3.8 support

openby mattytrentiniopened 2021-10-14updated 2025-10-03
py-core

This issue is intended to track the status of Python 3.8 core features as implemented by MicroPython.

Python 3.8.0 (final) was released on the 14 October 2019. The Features for 3.8 are defined in PEP 569 and a detailed description of the changes can be found in What's New in Python 3.8.

  • PEP 570, Positional-only arguments
  • PEP 572, Assignment Expressions; Done, see #4908
  • PEP 574, Pickle protocol 5 with out-of-band data
  • PEP 578, Runtime audit hooks
  • PEP 587, Python Initialization Configuration
  • PEP 590, Vectorcall: a fast calling protocol for CPython

Misc

  • f-strings support = for self-documenting expressions and debugging; Done, see #7649

Other language changes

  • A continue statement was illegal in the finally clause due to a problem with the implementation. In Python 3.8 this restriction was lifted; Done, see 82c494a97e874912e7eb23d2f03f39212e343fb3
  • The bool, int, and fractions.Fraction types now have an as_integer_ratio() method like that found in float and decimal.Decimal
  • Constructors of int, float and complex will now use the __index__() special method, if available and the corresponding method __int__(), __float__() or __complex__() is not available
  • Added support of \N{name} escapes in regular expressions
  • Dict and dictviews are now iterable in reversed insertion order using reversed()
  • The syntax allowed for keyword names in function calls was further restricted. In particular, f((keyword)=arg) is no longer allowed
  • Generalized iterable unpacking in yield and return statements no longer requires enclosing parentheses
  • When a comma is missed in code such as [(10, 20) (30, 40)], the compiler displays a SyntaxWarning with a helpful suggestion
  • Arithmetic operations between subclasses of datetime.date or datetime.datetime and datetime.timedelta objects now return an instance of the subclass, rather than the base class
  • When the Python interpreter is interrupted by Ctrl-C (SIGINT) and the resulting KeyboardInterrupt exception is not caught, the Python process now exits via a SIGINT signal or with the correct exit code such that the calling process can detect that it died due to a Ctrl-C
  • Some advanced styles of programming require updating the types.CodeType object for an existing function
  • For integers, the three-argument form of the pow() function now permits the exponent to be negative in the case where the base is relatively prime to the modulus
  • Dict comprehensions have been synced-up with dict literals so that the key is computed first and the value second
  • The object.__reduce__() method can now return a tuple from two to six elements long

Changes to MicroPython built-in modules

  • asyncio
    • asyncio.run() has graduated from the provisional to stable API
    • Running python -m asyncio launches a natively async REPL
    • The exception asyncio.CancelledError now inherits from BaseException rather than Exception and no longer inherits from concurrent.futures.CancelledError
    • Added asyncio.Task.get_coro() for getting the wrapped coroutine within an asyncio.Task
    • Asyncio tasks can now be named, either by passing the name keyword argument to asyncio.create_task() or the create_task() event loop method, or by calling the set_name() method on the task object
    • Added support for Happy Eyeballs to asyncio.loop.create_connection(). To specify the behavior, two new parameters have been added: happy_eyeballs_delay and interleave.
  • gc - get_objects() can now receive an optional generation parameter indicating a generation to get objects from
    • (Note, though, that while gc is a built-in, get_objects() is not implemented for MicroPython)
  • math
    • Added new function math.dist() for computing Euclidean distance between two points
    • Expanded the math.hypot() function to handle multiple dimensions
    • Added new function, math.prod(), as analogous function to sum() that returns the product of a ‘start’ value (default: 1) times an iterable of numbers
    • Added two new combinatoric functions math.perm() and math.comb()
    • Added a new function math.isqrt() for computing accurate integer square roots without conversion to floating point
    • The function math.factorial() no longer accepts arguments that are not int-like
  • sys - Add new sys.unraisablehook() function which can be overridden to control how “unraisable exceptions” are handled

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

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