.. _python_38:

Python 3.8

Python 3.8.0 (final) was released on the 14 October 2019. The Features for 3.8 are defined in PEP 569 <https://www.python.org/dev/peps/pep-0569/#id9>_ and a detailed description of the changes can be found in What's New in Python 3.8. <https://docs.python.org/3/whatsnew/3.8.html>_

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+--------------------------------------------------------+---------------------------------------------------+---------------+ | Features | Status | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 570 <https://www.python.org/dev/peps/pep-0570/>_ | Positional-only arguments | | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 572 <https://www.python.org/dev/peps/pep-0572/>_ | Assignment Expressions | Complete | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 574 <https://www.python.org/dev/peps/pep-0574/>_ | Pickle protocol 5 with out-of-band data | | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 578 <https://www.python.org/dev/peps/pep-0578/>_ | Runtime audit hooks | | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 587 <https://www.python.org/dev/peps/pep-0587/>_ | Python Initialization Configuration | | +--------------------------------------------------------+---------------------------------------------------+---------------+ | PEP 590 <https://www.python.org/dev/peps/pep-0590/>_ | Vectorcall: a fast calling protocol for CPython | | +--------------------------------------------------------+---------------------------------------------------+---------------+ | Miscellaneous | +------------------------------------------------------------------------------------------------------------+---------------+ | f-strings support = for self-documenting expressions and debugging | Complete | +------------------------------------------------------------------------------------------------------------+---------------+

Other Language Changes:

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+------------------------------------------------------------------------------------------------------------+-------------+ | A continue statement was illegal in the finally clause due to a problem with the implementation. In | Complete | | Python 3.8 this restriction was lifted | | +------------------------------------------------------------------------------------------------------------+-------------+ | 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 built-in modules:

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+------------------------------------------------------------------------------------------------------------+-------------+ | asyncio <https://docs.python.org/3/whatsnew/3.8.html#asyncio>_ | +------------------------------------------------------------------------------------------------------------+-------------+ | asyncio.run() has graduated from the provisional to stable API | Complete | +------------------------------------------------------------------------------------------------------------+-------------+ | Running python -m asyncio launches a natively async REPL | | +------------------------------------------------------------------------------------------------------------+-------------+ | The exception asyncio.CancelledError now inherits from BaseException rather than Exception and no | Complete | | 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 <https://docs.python.org/3/whatsnew/3.8.html#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 <https://docs.python.org/3/whatsnew/3.8.html#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 | Complete | +------------------------------------------------------------------------------------------------------------+-------------+ | sys <https://docs.python.org/3/whatsnew/3.8.html#sys>_ | +------------------------------------------------------------------------------------------------------------+-------------+ | Add new sys.unraisablehook() function which can be overridden to control how "unraisable exceptions" | | | are handled | | +------------------------------------------------------------------------------------------------------------+-------------+