Easy, clean, reliable Python 2/3 compatibility¶

python-future is the missing compatibility layer between Python 2 and Python 3. It allows you to use a single, clean Python 3.x-compatible codebase to support both Python 2 and Python 3 with minimal overhead.

Contents¶

• What’s New
  • What’s new in version 1.0.0 (2024年02月21日)
  • Previous versions
• Overview: Easy, clean, reliable Python 2/3 compatibility
  • Status
  • Features
  • Code examples
  • Automatic conversion to Py2/3-compatible code
    • Futurize: 2 to both
    • Automatic translation
    • Pre-commit hooks
  • Licensing
  • Docs
  • Next steps
• Quick-start guide
  • Installation
  • If you are writing code from scratch
  • To convert existing Python 3 code
  • To convert existing Python 2 code
  • Standard library reorganization
  • Python 2-only dependencies
  • Next steps
• Cheat Sheet: Writing Python 2-3 compatible code
  • Setup
  • Essential syntax differences
    • print
    • Raising exceptions
    • Catching exceptions
    • Division
    • Long integers
    • Octal constants
    • Backtick repr
    • Metaclasses
  • Strings and bytes
    • Unicode (text) string literals
    • Byte-string literals
    • basestring
    • unicode
    • StringIO
  • Imports relative to a package
  • Dictionaries
    • Iterating through dict keys/values/items
    • dict keys/values/items as a list
  • Custom class behaviour
    • Custom iterators
    • Custom __str__ methods
    • Custom __nonzero__ vs __bool__ method:
  • Lists versus iterators
    • xrange
    • range
    • map
    • imap
    • zip, izip
    • filter, ifilter
  • Other builtins
    • File IO with open()
    • reduce()
    • raw_input()
    • input()
    • file()
    • exec
    • execfile()
    • unichr()
    • intern()
    • apply()
    • chr()
    • cmp()
    • reload()
  • Standard library
    • dbm modules
    • commands / subprocess modules
    • StringIO module
    • http module
    • xmlrpc module
    • html escaping and entities
    • html parsing
    • urllib module
    • Tkinter
    • socketserver
    • copy_reg, copyreg
    • configparser
    • queue
    • repr, reprlib
    • UserDict, UserList, UserString
    • itertools: filterfalse, zip_longest
• Imports
  • __future__ imports
  • Imports of builtins
    • Implicit imports
    • Explicit imports
  • Standard library imports
    • Direct imports
    • Aliased imports
  • External standard-library backports
  • Included full backports
  • Using Python 2-only dependencies on Python 3
  • Should I import unicode_literals?
    • Benefits
    • Drawbacks
    • Others’ perspectives
  • Next steps
• What else you need to know
  • bytes
  • str
  • dict
    • Memory-efficiency and alternatives
  • int
  • isinstance
  • Passing data to/from Python 2 libraries
  • Native string type
  • open()
  • Custom __str__ methods
  • Custom iterators
  • Binding a method to a class
  • Metaclasses
• Automatic conversion to Py2/3
  • futurize: Py2 to Py2/3
    • Stage 1: "safe" fixes
    • Stage 2: Py3-style code with wrappers for Py2
    • Separating text from bytes
    • Post-conversion
  • futurize quick-start guide
    • Step 0: setup
    • Step 1: modern Py2 code
    • Step 2: working Py3 code that still supports Py2
  • pasteurize: Py3 to Py2/3
  • Known limitations
• Frequently Asked Questions (FAQ)
  • Who is this for?
  • Why upgrade to Python 3?
  • Porting philosophy
    • Why write Python 3-style code?
    • Can’t I just roll my own Py2/3 compatibility layer?
    • What inspired this project?
  • Maturity
    • How well has it been tested?
    • Is the API stable?
  • Relationship between python-future and other compatibility tools
    • How does this relate to 2to3?
    • Can I maintain a Python 2 codebase and use 2to3 to automatically convert to Python 3 in the setup script?
    • What is the relationship between future and six?
    • What is the relationship between python-future and python-modernize?
  • Platform and version support
    • Which versions of Python does python-future support?
  • Support
    • Is there a mailing list?
  • Contributing
    • Can I help?
    • Where is the repo?
• Standard library incompatibilities
  • array.array()
  • array.array.read()
  • base64.decodebytes() and base64.encodebytes()
  • re.ASCII
  • struct.pack()
• Older interfaces
  • future.moves interface
    • Comparing future.moves and six.moves
  • import_ and from_import functions
  • Context-manager for import hooks
  • install_hooks() call (deprecated)
• Changes in previous versions
  • Changes in version 0.18.3 (2023年01月13日)
  • Changes in version 0.18.2 (2019年10月30日)
  • Changes in version 0.18.1 (2019年10月09日)
  • Changes in version 0.18.0 (2019年10月09日)
  • Changes in version 0.17.1 (2018年10月30日)
  • Changes in version 0.17.0 (2018年10月19日)
  • Changes in version 0.16.0 (2016年10月27日)
  • Changes in version 0.15.2 (2015年09月11日)
  • Changes in version 0.15.1 (2015年09月09日)
  • Changes in version 0.15.0 (2015年07月25日)
  • Changes in version 0.14.3 (2014年12月15日)
  • Changes in version 0.14.2 (2014年11月21日)
  • Changes in version 0.14.1 (2014年10月02日)
  • Changes in version 0.14.0 (2014年10月02日)
    • Bug fixes
    • Internal cleanups
    • Deprecations
  • Changes in version 0.13.1 (2014年09月23日)
  • Changes in version 0.13.0 (2014年08月13日)
    • Deprecations
    • New features
    • Bug fixes
  • Changes in version 0.12.4 (2014年07月18日)
  • Changes in version 0.12.3 (2014年06月19日)
  • Changes in version 0.12.2 (2014年05月25日)
  • Changes in version 0.12.1 (2014年05月14日)
  • Changes in version 0.12.0 (2014年05月06日)
    • More robust standard-library import hooks
    • newobject base object defines fallback Py2-compatible special methods
    • past.builtins module improved
    • surrogateescape error handler
    • newlist type
    • listvalues and listitems
    • Tests
    • Refactoring of future.standard_library.* -> future.backports
    • Backported http.server and urllib modules
    • Internal refactoring
    • Bug fixes
  • Changes in version 0.11.4 (2014年05月25日)
  • Changes in version 0.11.3 (2014年02月27日)
    • Improved compatibility with requests
    • Conversion scripts explicitly install import hooks
    • futurize script no longer adds unicode_literals by default
  • Changes in version 0.11 (2014年01月28日)
    • past package
    • Auto-translation of Python 2 modules upon import
    • Separate pasteurize script
    • pow()
    • input() no longer disabled globally on Py2
    • Deprecated feature: auto-installation of standard-library import hooks
    • Internal changes
  • Changes in version 0.10.2 (2014年01月11日)
    • New context-manager interface to standard_library.hooks
  • Changes in version 0.10.0 (2013年12月02日)
    • Backported dict type
    • Utility functions raise_ and exec_
    • Bugfixes
  • Changes in version 0.9 (2013年11月06日)
    • isinstance checks are supported natively with backported types
    • futurize: minimal imports by default
    • Looser type-checking for the backported str object
    • suspend_hooks() context manager added to future.standard_library
  • Changes in version 0.8 (2013年10月28日)
    • Python 2.6 support
    • Unused modules removed
    • isinstance() added to future.builtins (v0.8.2)
  • Summary of all changes
• Licensing and credits
  • Licence
  • Sponsors
  • Author
  • Maintainers
  • Contributors
    • Suggestions and Feedback
  • Other Credits
• API Reference (in progress)
  • future.builtins Interface
  • Backported types from Python 3
    • For more information:
    • range()
    • super()
    • round()
  • future.standard_library Interface
    • Limitations
    • RenameImport
    • cache_py2_modules()
    • detect_hooks()
    • disable_hooks()
    • enable_hooks()
    • exclude_local_folder_imports
    • from_import()
    • hooks
    • import_()
    • install_aliases()
    • install_hooks()
    • is_py2_stdlib_module()
    • remove_hooks()
    • restore_sys_modules()
    • scrub_future_sys_modules()
    • scrub_py2_sys_modules()
    • suspend_hooks
  • future.utils Interface
    • as_native_str()
    • binary_type
    • bind_method()
    • exec_()
    • implements_iterator()
    • is_new_style()
    • isbytes()
    • isidentifier()
    • isint()
    • isnewbytes()
    • istext()
    • iteritems()
    • iterkeys()
    • itervalues()
    • native()
    • native_bytes
    • native_str
    • native_str_to_bytes()
    • old_div()
    • python_2_unicode_compatible()
    • raise_()
    • raise_with_traceback()
    • reraise()
    • text_type
    • tobytes()
    • viewitems()
    • viewkeys()
    • viewvalues()
    • with_metaclass()
  • past.builtins Interface
    • basestring
    • chr()
    • cmp()
    • dict
    • execfile()
    • filter()
    • intern()
    • long
    • map()
    • raw_input()
    • reduce()
    • reload()
    • str
    • unichr()
    • unicode
    • xrange
  • Forward-ported types from Python 2
    • basestring
    • long
    • olddict
    • oldstr
    • unicode

Indices and tables¶

• Index

• Module Index

• Search Page