Welcome! This is the official documentation for Python 3.9.24.

For unreleased (in development) documentation, see In development versions. Python 3.14.3, released on 3 February 2026 · Python 3.14.2, released on 5 December 2025 · Python 3.14.1, released on 2 December 2025 · Python 3.14.0, released on 7 October 2025 · Python 3.13.12, released on 3 February 2026 · Python 3.13.11, released on 5 December 2025 · Python 3.13.10, released on 2 December 2025 · Python 3.13.9, released on 14 October 2025 ·

Python 3.9 is the last version providing those Python 2 backward compatibility layers, to give more time to Python projects maintainers to organize the removal of the Python 2 support and add support for Python 3.9.

September 3, 2014 - Python 3.9.14 API documentation with instant search, offline support, keyboard shortcuts, mobile version, and more.

/Python 3.9 · While The Python Language Reference describes the exact syntax and semantics of the Python language, this library reference manual describes the standard library that is distributed with Python. It also describes some of the optional components that are commonly included in Python distributions.

Download these documents · Python 3.15 (in development) Python 3.14 (stable) Python 3.13 (stable) Python 3.12 (security-fixes) Python 3.11 (security-fixes) Python 3.10 (security-fixes) Python 3.9 (EOL) Python 3.8 (EOL) Python 3.7 (EOL) Python 3.6 (EOL) Python 3.5 (EOL) Python 3.4 (EOL) Python 3.3 (EOL) Python 3.2 (EOL) Python 3.1 (EOL) Python 3.0 (EOL) Python 2.7 (EOL) Python 2.6 (EOL) All versions ·

The Features for 3.9 are defined in PEP 596 and a detailed description of the changes can be found in What’s New in Python 3.9

Download Current Documentation (multiple formats are available, including typeset versions for printing.) FAQ: Sunsetting Python 2 · Final Python 2.7 Release Schedule · Python 3 Statement · Porting Python 2 Code to Python 3 · Determine what projects are blocking you from porting to Python 3 ·

This document is for an old version of Python that is no longer supported. You should upgrade, and read the Python documentation for the current stable release. index · modules | Python » · 3.9.24 Documentation » · | Last updated on: Nov 01, 2025. To download an archive containing all the documents for this version of Python in one of various formats, follow one of links in this table.

4 weeks ago - Download an archive containing all the documentation for this version of Python:

Online Documentation · PEP 596, 3.9 Release Schedule · Report bugs at https://bugs.python.org. Help fund Python and its community. Wapcaplet: (John Cleese) Welcome! Do sit down. My name's Wapcaplet, Adrian Wapcaplet. Mr. Simpson: how'd'y'do. Wapcaplet: Now, Mr.

July 31, 2023 - In this tutorial, you'll explore some of the coolest and most useful features in Python 3.9. You'll learn how Python 3.9 makes it easier to work with time zones, dictionaries, decorators, and several other techniques that will make your code cleaner and more efficient.

--- /home/docs/checkouts/readthedocs.org/user_builds/restrictedpython/checkouts/latest/docs/contributing/ast/python3_8.ast +++ /home/docs/checkouts/readthedocs.org/user_builds/restrictedpython/checkouts/latest/docs/contributing/ast/python3_9.ast @@ -1,16 +1,13 @@ --- Python 3.8 AST --- ASDL's 5 builtin types are: --- identifier, int, string, object, constant +-- Python 3.9 AST +-- ASDL's 4 builtin types are: +-- identifier, int, string, constant -module Python version "3.8" +module Python version "3.9" { - mod = Module(stmt* body, type_ignore *type_ignores) + mod = Module(stmt* body, type_ignore* type_ignores) | Interactive(stmt* body) | Expression(expr body) | FunctionType(expr* argtypes, expr returns) - - -- not really an actual node but useful in Jython's typesystem.

Download these documents · Python 3.15 (in development) Python 3.14 (stable) Python 3.13 (stable) Python 3.12 (security-fixes) Python 3.11 (security-fixes) Python 3.10 (security-fixes) Python 3.9 (EOL) Python 3.8 (EOL) Python 3.7 (EOL) Python 3.6 (EOL) Python 3.5 (EOL) Python 3.4 (EOL) Python 3.3 (EOL) Python 3.2 (EOL) Python 3.1 (EOL) Python 3.0 (EOL) Python 2.7 (EOL) Python 2.6 (EOL) All versions ·

If you’re on an apt-based system, the deadsnakes package has already been updated to include Python 3.9. If you haven’t already used deadsnakes, add it to your system: ... You should now be able to use the command python3.9 to run programs using the Python 3.9 interpreter.

4.9.3.5. Recap · 4.9.4. Arbitrary Argument Lists · 4.9.5. Unpacking Argument Lists · 4.9.6. Lambda Expressions · 4.9.7. Documentation Strings · 4.9.8. Function Annotations · 4.10. Intermezzo: Coding Style · 5. Data Structures · 5.1. More on Lists · 5.1.1. Using Lists as Stacks ·

October 9, 2020 - Python 3.9 is the last version providing those Python 2 backward compatibility layers, to give more time to Python projects maintainers to organize the removal of the Python 2 support and add support for Python 3.9.

See Python Initialization Configuration for the documentation. See PEP 587 for a full description. ... The Vectorcall Protocol is added to the Python/C API. It is meant to formalize existing optimizations which were already done for various classes.

Python 3.14.3 API documentation with instant search, offline support, keyboard shortcuts, mobile version, and more.

What’s New In Python 3.9 · Summary – Release highlights · You should check for DeprecationWarning in your code · New Features · Other Language Changes · New Modules · Improved Modules · Optimizations · Deprecated · Removed · Porting to Python 3.9 ·