Python/docs/3.9/whatsnew/index

What's New in Python

The "What's New in Python" series of essays takes tours through the most important changes between major Python versions. They are a "must read" for anyone wishing to stay up-to-date after a new release.

• 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
  • Build Changes
  • C API Changes
  • Notable changes in Python 3.9.1
• What's New In Python 3.8
  • Summary -- Release highlights
  • New Features
  • Other Language Changes
  • New Modules
  • Improved Modules
  • Optimizations
  • Build and C API Changes
  • Deprecated
  • API and Feature Removals
  • Porting to Python 3.8
  • Notable changes in Python 3.8.1
• What's New In Python 3.7
  • Summary -- Release Highlights
  • New Features
  • Other Language Changes
  • New Modules
  • Improved Modules
  • C API Changes
  • Build Changes
  • Optimizations
  • Other CPython Implementation Changes
  • Deprecated Python Behavior
  • Deprecated Python modules, functions and methods
  • Deprecated functions and types of the C API
  • Platform Support Removals
  • API and Feature Removals
  • Module Removals
  • Windows-only Changes
  • Porting to Python 3.7
  • Notable changes in Python 3.7.1
  • Notable changes in Python 3.7.2
  • Notable changes in Python 3.7.6
• What's New In Python 3.6
  • Summary -- Release highlights
  • New Features
  • Other Language Changes
  • New Modules
  • Improved Modules
  • Optimizations
  • Build and C API Changes
  • Other Improvements
  • Deprecated
  • Removed
  • Porting to Python 3.6
  • Notable changes in Python 3.6.2
  • Notable changes in Python 3.6.4
  • Notable changes in Python 3.6.5
  • Notable changes in Python 3.6.7
  • Notable changes in Python 3.6.10
• What's New In Python 3.5
  • Summary -- Release highlights
  • New Features
  • Other Language Changes
  • New Modules
  • Improved Modules
  • Other module-level changes
  • Optimizations
  • Build and C API Changes
  • Deprecated
  • Removed
  • Porting to Python 3.5
  • Notable changes in Python 3.5.4
• What's New In Python 3.4
  • Summary -- Release Highlights
  • New Features
  • New Modules
  • Improved Modules
  • CPython Implementation Changes
  • Deprecated
  • Removed
  • Porting to Python 3.4
  • Changed in 3.4.3
• What's New In Python 3.3
  • Summary -- Release highlights
  • PEP 405: Virtual Environments
  • PEP 420: Implicit Namespace Packages
  • PEP 3118: New memoryview implementation and buffer protocol documentation
  • PEP 393: Flexible String Representation
  • PEP 397: Python Launcher for Windows
  • PEP 3151: Reworking the OS and IO exception hierarchy
  • PEP 380: Syntax for Delegating to a Subgenerator
  • PEP 409: Suppressing exception context
  • PEP 414: Explicit Unicode literals
  • PEP 3155: Qualified name for classes and functions
  • PEP 412: Key-Sharing Dictionary
  • PEP 362: Function Signature Object
  • PEP 421: Adding sys.implementation
  • Using importlib as the Implementation of Import
  • Other Language Changes
  • A Finer-Grained Import Lock
  • Builtin functions and types
  • New Modules
  • Improved Modules
  • Optimizations
  • Build and C API Changes
  • Deprecated
  • Porting to Python 3.3
• What's New In Python 3.2
  • PEP 384: Defining a Stable ABI
  • PEP 389: Argparse Command Line Parsing Module
  • PEP 391: Dictionary Based Configuration for Logging
  • PEP 3148: The concurrent.futures module
  • PEP 3147: PYC Repository Directories
  • PEP 3149: ABI Version Tagged .so Files
  • PEP 3333: Python Web Server Gateway Interface v1.0.1
  • Other Language Changes
  • New, Improved, and Deprecated Modules
  • Multi-threading
  • Optimizations
  • Unicode
  • Codecs
  • Documentation
  • IDLE
  • Code Repository
  • Build and C API Changes
  • Porting to Python 3.2
• What's New In Python 3.1
  • PEP 372: Ordered Dictionaries
  • PEP 378: Format Specifier for Thousands Separator
  • Other Language Changes
  • New, Improved, and Deprecated Modules
  • Optimizations
  • IDLE
  • Build and C API Changes
  • Porting to Python 3.1
• What's New In Python 3.0
  • Common Stumbling Blocks
  • Overview Of Syntax Changes
  • Changes Already Present In Python 2.6
  • Library Changes
  • PEP 3101: A New Approach To String Formatting
  • Changes To Exceptions
  • Miscellaneous Other Changes
  • Build and C API Changes
  • Performance
  • Porting To Python 3.0
• What's New in Python 2.7
  • The Future for Python 2.x
  • Changes to the Handling of Deprecation Warnings
  • Python 3.1 Features
  • PEP 372: Adding an Ordered Dictionary to collections
  • PEP 378: Format Specifier for Thousands Separator
  • PEP 389: The argparse Module for Parsing Command Lines
  • PEP 391: Dictionary-Based Configuration For Logging
  • PEP 3106: Dictionary Views
  • PEP 3137: The memoryview Object
  • Other Language Changes
  • New and Improved Modules
  • Build and C API Changes
  • Other Changes and Fixes
  • Porting to Python 2.7
  • New Features Added to Python 2.7 Maintenance Releases
  • Acknowledgements
• What's New in Python 2.6
  • Python 3.0
  • Changes to the Development Process
  • PEP 343: The 'with' statement
  • PEP 366: Explicit Relative Imports From a Main Module
  • PEP 370: Per-user site-packages Directory
  • PEP 371: The multiprocessing Package
  • PEP 3101: Advanced String Formatting
  • PEP 3105: print As a Function
  • PEP 3110: Exception-Handling Changes
  • PEP 3112: Byte Literals
  • PEP 3116: New I/O Library
  • PEP 3118: Revised Buffer Protocol
  • PEP 3119: Abstract Base Classes
  • PEP 3127: Integer Literal Support and Syntax
  • PEP 3129: Class Decorators
  • PEP 3141: A Type Hierarchy for Numbers
  • Other Language Changes
  • New and Improved Modules
  • Deprecations and Removals
  • Build and C API Changes
  • Porting to Python 2.6
  • Acknowledgements
• What's New in Python 2.5
  • PEP 308: Conditional Expressions
  • PEP 309: Partial Function Application
  • PEP 314: Metadata for Python Software Packages v1.1
  • PEP 328: Absolute and Relative Imports
  • PEP 338: Executing Modules as Scripts
  • PEP 341: Unified try/except/finally
  • PEP 342: New Generator Features
  • PEP 343: The 'with' statement
  • PEP 352: Exceptions as New-Style Classes
  • PEP 353: Using ssize_t as the index type
  • PEP 357: The '__index__' method
  • Other Language Changes
  • New, Improved, and Removed Modules
  • Build and C API Changes
  • Porting to Python 2.5
  • Acknowledgements
• What's New in Python 2.4
  • PEP 218: Built-In Set Objects
  • PEP 237: Unifying Long Integers and Integers
  • PEP 289: Generator Expressions
  • PEP 292: Simpler String Substitutions
  • PEP 318: Decorators for Functions and Methods
  • PEP 322: Reverse Iteration
  • PEP 324: New subprocess Module
  • PEP 327: Decimal Data Type
  • PEP 328: Multi-line Imports
  • PEP 331: Locale-Independent Float/String Conversions
  • Other Language Changes
  • New, Improved, and Deprecated Modules
  • Build and C API Changes
  • Porting to Python 2.4
  • Acknowledgements
• What's New in Python 2.3
  • PEP 218: A Standard Set Datatype
  • PEP 255: Simple Generators
  • PEP 263: Source Code Encodings
  • PEP 273: Importing Modules from ZIP Archives
  • PEP 277: Unicode file name support for Windows NT
  • PEP 278: Universal Newline Support
  • PEP 279: enumerate()
  • PEP 282: The logging Package
  • PEP 285: A Boolean Type
  • PEP 293: Codec Error Handling Callbacks
  • PEP 301: Package Index and Metadata for Distutils
  • PEP 302: New Import Hooks
  • PEP 305: Comma-separated Files
  • PEP 307: Pickle Enhancements
  • Extended Slices
  • Other Language Changes
  • New, Improved, and Deprecated Modules
  • Pymalloc: A Specialized Object Allocator
  • Build and C API Changes
  • Other Changes and Fixes
  • Porting to Python 2.3
  • Acknowledgements
• What's New in Python 2.2
  • Introduction
  • PEPs 252 and 253: Type and Class Changes
  • PEP 234: Iterators
  • PEP 255: Simple Generators
  • PEP 237: Unifying Long Integers and Integers
  • PEP 238: Changing the Division Operator
  • Unicode Changes
  • PEP 227: Nested Scopes
  • New and Improved Modules
  • Interpreter Changes and Fixes
  • Other Changes and Fixes
  • Acknowledgements
• What's New in Python 2.1
  • Introduction
  • PEP 227: Nested Scopes
  • PEP 236: __future__ Directives
  • PEP 207: Rich Comparisons
  • PEP 230: Warning Framework
  • PEP 229: New Build System
  • PEP 205: Weak References
  • PEP 232: Function Attributes
  • PEP 235: Importing Modules on Case-Insensitive Platforms
  • PEP 217: Interactive Display Hook
  • PEP 208: New Coercion Model
  • PEP 241: Metadata in Python Packages
  • New and Improved Modules
  • Other Changes and Fixes
  • Acknowledgements
• What's New in Python 2.0
  • Introduction
  • What About Python 1.6?
  • New Development Process
  • Unicode
  • List Comprehensions
  • Augmented Assignment
  • String Methods
  • Garbage Collection of Cycles
  • Other Core Changes
  • Porting to 2.0
  • Extending/Embedding Changes
  • Distutils: Making Modules Easy to Install
  • XML Modules
  • Module changes
  • New modules
  • IDLE Improvements
  • Deleted and Deprecated Modules
  • Acknowledgements

The "Changelog" is an HTML version of the file built from the contents of the Misc/NEWS.d directory tree, which contains all nontrivial changes to Python for the current version.

• Changelog