The Question Mark - blog by Mark Volkmann

Python versions

This page documents the most significant additions and changes in each version of Python starting with version 3.0. If I have omitted changes that you feel are significant, please let me know and I will add them.

Python 3.0 - December 3, 2008

  • Strings now use Unicode instead of ASCII.

  • The print keyword was replaced by the print function.

  • The <> operator was removed. Use != instead.

  • Some functions and methods now return “views” (like an iterator) instead of a list object.

  • The long type was renamed to int.

  • Expressions like 1 / 2 now return a float instead of an int.

  • The __cmp__ method is no longer supported and the cmp function should not be used.

  • The default encoding for source code is now UTF-8.

  • Non-ASCII letters are now allowed in identifiers.

  • The StringIO module is now inio.StringIO.

  • Annotations can be added to function arguments and to functions to describe their return value. The goal is to enable future tooling to use the annotations for purposes such as type checking and documentation generation.

  • The nonlocal statement was added to allow functions to access non-local, non-global values.

  • Iterable unpacking was added. For example:

    a, b *rest = data
a, *rest, b = data
*rest, a, b = data

  • Support for tuple unpacking in parameter lists was removed.

  • List comprehension syntax changed slightly.

  • Dictionary comprehensions were added.

  • Support for set literals was added. For example, {'one', 'two', 'three'}

  • Set comprehensions were added.

  • Exception catching syntax changed from exception ErrorName, var_name is now exception ErrorName as var_name

Python 3.1 - June 27, 2009

  • The OrderedDict class was added in the collections module.
  • New features were added to unittest including test skipping and new assert methods.
  • tile support was added to tkinter
  • Support for a new syntax for nested with statements.

Python 3.2 - February 20, 2011

  • The concurrent.futures module was added to support concurrent programming.
  • Additions were made to the shutil module.
  • The sysconfig module was added.
  • The argparse command-line parsing module was added.
  • Improvements were made to the pdb debugger.

Python 3.3 - September 29, 2012

  • The unittest.mock module was added to support implementing mock objects used by tests.
  • The venv command for managing virtual environments was added.
  • Support for generator delegation was added via yield from expressions.

Python 3.4 - March 16, 2014

  • The asyncio module was added.
  • The enum module was added.
  • The pathlib module was added.
  • The selectors module was added.
  • The statistics module was added.

Python 3.5 - September 13, 2015

  • The typing module for type hints was added.
  • A new exception class, RecursionError, was added.
  • Support for coroutines with async and await was added.
  • Support for the matrix multiplication operator @ was added. It not supported by built-in data types such as nested lists, but is supported by NumPy.

Python 3.6 - December 23, 2016

  • Support for formatting string literals (a.k.a. f-strings) with the syntax (f'...') was added.
  • Support for underscores in numeric literals was added. Single underscores can be added anywhere inside a literal number for readability and they are ignored.
  • Support for variable annotations was added.
  • Support for async comprehensions was added.
  • Support for async generators was added.
  • The secrets module was added.

Python 3.7 - June 27, 2018

  • The contextvar module was added.
  • The dateclasses module was added.
  • The breakpoint function was added.
  • Preserving insertion order in dict objects was made official.
  • The time module gained functions for nanosecond resolution.

Python 3.8 - October 14, 2019

  • Support for the := “walrus operator” for assignments inside expressions was added.
  • Support for position-only parameters with / syntax was added.
  • Support for the = specifier was added to f-strings.

Python 3.9 - October 5, 2020

  • The string methods removeprefix and removesuffix were added.
  • Support for the union operators | and |= for merging dict objects was added.
  • The ability to add generics type hinting in standard collections was added.
  • Python code is now parsed by a new PEG parser.
  • An IANA Time Zone Database was added in the zoneinfo module.
  • The graphlib module was added, with support for topological sorting.
  • CPython will adopt an annual release cycle (like ECMAScript).