Changes in previous versions

Changes in the most recent major version are here: What’s New.

Changes in version 0.18.3 (2023-01-13)

This is a minor bug-fix release containing a number of fixes:

  • Backport fix for bpo-38804 (c91d70b)

  • Fix bug in fixer (dffc579)

  • Fix bug in fixer (3401099)

  • Fix newint bool in py3 (fe645ba)

  • Fix bug in super() with metaclasses (6e27aac)

  • docs: fix simple typo, reqest -> request (974eb1f)

  • Correct __eq__ (c780bf5)

  • Pass if lint fails (2abe00d)

  • Update docker image and parcel out to constant variable. Add comment to update version constant (45cf382)

  • fix order (f96a219)

  • Add flake8 to image (046ff18)

  • Make executable (58cc984)

  • Add docker push to optimize CI (01e8440)

  • Build System (42b3025)

  • Add docs build status badge to (3f40bd7)

  • Use same docs requirements in tox (18ecc5a)

  • Add docs/requirements.txt (5f9893f)

  • Add PY37_PLUS, PY38_PLUS, and PY39_PLUS (bee0247)

  • fix 2.6 test, better comment (ddedcb9)

  • fix 2.6 test (3f1ff7e)

  • remove nan test (4dbded1)

  • include list test values (e3f1a12)

  • fix other python2 test issues (c051026)

  • fix missing subTest (f006cad)

  • import from old imp library on older python versions (fc84fa8)

  • replace fstrings with format for python 3.4,3.5 (4a687ea)

  • minor style/spelling fixes (8302d8c)

  • improve cmp function, add unittest (0d95a40)

  • Pin typing== for Python 3.3 compatiblity (1a48f1b)

  • Fix various py26 unit test failures (9ca5a14)

  • Add initial contributing guide with docs build instruction (e55f915)

  • Add docs building to tox.ini (3ee9e7f)

  • Support NumPy’s specialized int types in builtins.round (b4b54f0)

  • Added r””” to the docstring to avoid warnings in python3 (5f94572)

  • Add __subclasscheck__ for past.types.basestring (c9bc0ff)

  • Correct example in README (681e78c)

  • Add simple documentation (6c6e3ae)

  • Add pre-commit hooks (a9c6a37)

  • Handling of __next__ and next by future.utils.get_next was reversed (52b0ff9)

  • Add a test for our fix (461d77e)

  • Compare headers to correct definition of str (3eaa8fd)

  • #322 Add support for negative ndigits in round; additionally, fixing a bug so that it handles passing in Decimal properly (a4911b9)

  • Add tkFileDialog to future.movers.tkinter (f6a6549)

  • Sort before comparing dicts in TestChainMap (6126997)

  • Fix typo (4dfa099)

  • Fix formatting in “What’s new” (1663dfa)

  • Fix typo (4236061)

  • Avoid DeprecationWarning caused by invalid escape (e4b7fa1)

  • Fixup broken link to external django documentation re: porting to Python 3 and unicode_literals (d87713e)

  • Fixed newdict checking version every time (99030ec)

  • Add count from 2.7 to 2.6 (1b8ef51)

Changes in version 0.18.2 (2019-10-30)

This is a minor bug-fix release containing a number of fixes:

  • Fix min/max functions with generators, and ‘None’ default (PR #514)

  • Use BaseException in raise_() (PR #515)

  • Fix builtins.round() for Decimals (Issue #501)

  • Fix raise_from() to prevent failures with immutable classes (PR #518)

  • Make FixInput idempotent (Issue #427)

  • Fix type in newround (PR #521)

  • Support mimetype guessing in urllib2 for Py3.8+ (Issue #508)

Python 3.8 is not yet officially supported.

Changes in version 0.18.1 (2019-10-09)

This is a minor bug-fix release containing a fix for raise_() when passed an exception that’s not an Exception (e.g. BaseException subclasses)

Changes in version 0.18.0 (2019-10-09)

This is a major bug-fix and feature release, including:

  • Fix import for py38+

  • Remove import for isnewbytes() function, reducing CPU cost significantly

  • Fix bug with importing past.translation when importing past which breaks zipped python installations

  • Fix an issue with copyreg import under Py3 that results in unexposed stdlib functionality

  • Export and document types in future.utils

  • Update behavior of newstr.__eq__() to match str.__eq__() as per reference docs

  • Fix raising and the raising fixer to handle cases where the syntax is ambiguous

  • Allow “default” parameter in min() and max() (Issue #334)

  • Implement __hash__() in newstr (Issue #454)

  • Future proof some version checks to handle the fact that Py4 won’t be a major breaking release

  • Fix urllib.request imports for Python 3.8 compatibility (Issue #447)

  • Fix future import ordering (Issue #445)

  • Fixed bug in fix_division_safe fixture (Issue #434)

  • Do not globally destroy re.ASCII in PY3

  • Fix a bug in email.Message.set_boundary() (Issue #429)

  • Implement format_map() in str

  • Implement readinto() for socket.fp

As well as a number of corrections to a variety of documentation, and updates to test infrastructure.

Changes in version 0.17.1 (2018-10-30)

This release address a packaging error because of an erroneous declaration that any built wheels are universal.

Changes in version 0.17.0 (2018-10-19)

This is a major bug-fix release, including:

  • Fix from collections import ChainMap after install_aliases() (issue #226)

  • Fix multiple import from __future__ bug in futurize (issue #113)

  • Add support for proper %s formatting of newbytes

  • Properly implement iterator protocol for newrange object

  • Fix past.translation on read-only file systems

  • Fix Tkinter import bug introduced in Python 2.7.4 (issue #262)

  • Correct TypeError to ValueError in a specific edge case for newrange

  • Support inequality tests between newstrs and newbytes

  • Add type check to __get__ in newsuper

  • Fix fix_divsion_safe to support better conversion of complex expressions, and skip obvious float division.

As well as a number of corrections to a variety of documentation, and updates to test infrastructure.

Changes in version 0.16.0 (2016-10-27)

This release removes the configparser package as an alias for ConfigParser on Py2 to improve compatibility with the backported configparser package <>. Previously python-future and the PyPI configparser backport clashed, causing various compatibility issues. (Issues #118, #181)

If your code previously relied on configparser being supplied by python-future, the recommended upgrade path is to run pip install configparser or add configparser to your requirements.txt file.

Note that, if you are upgrading future with pip, you may need to uninstall the old version of future or manually remove the site-packages/future-0.15.2-py2.7.egg folder for this change to take effect on your system.

This releases also fixes these bugs:

  • Fix newbytes constructor bug. (Issue #171)

  • Fix semantics of bool() with newobject. (Issue #211)

  • Fix standard_library.install_aliases() on PyPy. (Issue #205)

  • Fix assertRaises for pow and compile` on Python 3.5. (Issue #183)

  • Fix return argument of future.utils.ensure_new_type if conversion to new type does not exist. (Issue #185)

  • Add missing cmp_to_key for Py2.6. (Issue #189)

  • Allow the old_div fixer to be disabled. (Issue #190)

  • Improve compatibility with Google App Engine. (Issue #231)

  • Add some missing imports to the tkinter and tkinter.filedialog package namespaces. (Issues #212 and #233)

  • More complete implementation of raise_from on PY3. (Issues #141, #213 and #235, fix provided by Varriount)

Changes in version 0.15.2 (2015-09-11)

This is a minor bug-fix release:

  • Fix socket.create_connection() backport on Py2.6 (issue #162)

  • Add more tests of urllib.request etc.

  • Fix newsuper() calls from the __init__ method of PyQt subclassses (issue #160, thanks to Christopher Arndt)

Changes in version 0.15.1 (2015-09-09)

This is a minor bug-fix release:

  • Use 3-argument socket.create_connection() backport to restore Py2.6 compatibility in urllib.request.urlopen() (issue #162)

  • Remove breakpoint in future.backports.http.client triggered on certain data (issue #164)

  • Move exec fixer to stage 1 of futurize because the forward-compatible exec(a, b) idiom is supported in Python 2.6 and 2.7. See

Changes in version 0.15.0 (2015-07-25)

This release fixes compatibility bugs with CherryPy’s Py2/3 compat layer and the latest version of the urllib3 package. It also adds some additional backports for Py2.6 and Py2.7 from Py3.4’s standard library.

New features:

  • install_aliases() now exposes full backports of the Py3 urllib submodules (parse, request etc.) from future.backports.urllib as submodules of urllib on Py2. This implies, for example, that urllib.parse.unquote now takes an optional encoding argument as it does on Py3. This improves compatibility with CherryPy’s Py2/3 compat layer (issue #158).

  • tkinter.ttk support (issue #151)

  • Backport of collections.ChainMap (issue #150)

  • Backport of itertools.count for Py2.6 (issue #152)

  • Enable and document support for the surrogateescape error handler for newstr and newbytes objects on Py2.x (issue #116). This feature is currently in alpha.

  • Add constants to http.client such as HTTP_PORT and BAD_REQUEST (issue #137)

  • Backport of reprlib.recursive_repr to Py2

Bug fixes:

  • Add HTTPMessage to http.client, which is missing from httplib.__all__ on Python <= 2.7.10. This restores compatibility with the latest urllib3 package (issue #159, thanks to Waldemar Kornewald)

  • Expand newint.__divmod__ and newint.__rdivmod__ to fall back to <type ‘long’> implementations where appropriate (issue #146 - thanks to Matt Bogosian)

  • Fix newrange slicing for some slice/range combos (issue #132, thanks to Brad Walker)

  • Small doc fixes (thanks to Michael Joseph and Tim Tröndle)

  • Improve robustness of test suite against opening .pyc files as text on Py2

  • Update backports of Counter and OrderedDict to use the newer implementations from Py3.4. This fixes .copy() preserving subclasses etc.

  • futurize no longer breaks working Py2 code by changing basestring to str. Instead it imports the basestring forward-port from past.builtins (issues #127 and #156)

  • future.utils: add string_types etc. and update docs (issue #126)

Changes in version 0.14.3 (2014-12-15)

This is a bug-fix release:

  • Expose contents of thread (not dummy_thread) as _thread on Py2 (Issue #124)

  • Add signed support for newint.to_bytes() (Issue #128)

  • Fix OrderedDict.clear() on Py2.6 (Issue #125)

  • Improve newrange: equality and slicing, start/stop/step properties, refactoring (Issues #129, #130)

  • Minor doc updates

Changes in version 0.14.2 (2014-11-21)

This is a bug-fix release:

  • Speed up importing of past.translation (Issue #117)

  • html.escape(): replace function with the more robust one from Py3.4

  • futurize: avoid displacing encoding comments by __future__ imports (Issues #97, #10, #121)

  • futurize: don’t swallow exit code (Issue #119)

  • Packaging: don’t forcibly remove the old build dir in (Issue #108)

  • Docs: update further docs and tests to refer to install_aliases() instead of install_hooks()

  • Docs: fix iteritems import error in cheat sheet (Issue #120)

  • Tests: don’t rely on presence of test.test_support on Py2 or on Py3 (Issue #109)

  • Tests: don’t override existing PYTHONPATH for tests (PR #111)

Changes in version 0.14.1 (2014-10-02)

This is a minor bug-fix release:

  • Docs: add a missing template file for building docs (Issue #108)

  • Tests: fix a bug in error handling while reporting failed script runs (Issue #109)

  • install_aliases(): don’t assume that the test.test_support module always exists on Py2 (Issue #109)

Changes in version 0.14.0 (2014-10-02)

This is a major new release that offers a cleaner interface for most imports in Python 2/3 compatible code.

Instead of this interface:

>>> from future.builtins import str, open, range, dict

>>> from future.standard_library import hooks
>>> with hooks():
...     import queue
...     import configparser
...     import tkinter.dialog
...     # etc.

You can now use the following interface for much Python 2/3 compatible code:

>>> # Alias for future.builtins on Py2:
>>> from builtins import str, open, range, dict

>>> # Alias for future.moves.* on Py2:
>>> import queue
>>> import configparser
>>> import tkinter.dialog
>>> etc.

Notice that the above code will run on Python 3 even without the presence of the future package. Of the 44 standard library modules that were refactored with PEP 3108, 30 are supported with direct imports in this manner. (These are listed here: Direct imports.)

The other 14 standard library modules that kept the same top-level names in Py3.x are not supported with this direct import interface on Py2. These include the 5 modules in the Py3 urllib package. These modules are accessible through the following interface (as well as the interfaces offered in previous versions of python-future):

from future.standard_library import install_aliases

from collections import UserDict, UserList, UserString
import dbm.gnu
from itertools import filterfalse, zip_longest
from subprocess import getoutput, getstatusoutput
from sys import intern
from urllib.request import urlopen
from urllib.parse import urlparse
# etc.
from collections import Counter, OrderedDict     # backported to Py2.6

The complete list of packages supported with this interface is here: Aliased imports.

For more information on these and other interfaces to the standard library, see Standard library imports.

Bug fixes

  • This release expands the future.moves package to include most of the remaining modules that were moved in the standard library reorganization (PEP 3108). (Issue #104)

  • This release also removes the broken --doctests_only option from the futurize and pasteurize scripts for now. (Issue #103)

Internal cleanups

The project folder structure has changed. Top-level packages are now in a src folder and the tests have been moved into a project-level tests folder.

The following deprecated internal modules have been removed (Issue #80):

  • future.utils.encoding and future.utils.six.


The following internal functions have been deprecated and will be removed in a future release:

  • future.standard_library.scrub_py2_sys_modules

  • future.standard_library.scrub_future_sys_modules

Changes in version 0.13.1 (2014-09-23)

This is a bug-fix release:

  • Fix (multiple) inheritance of future.builtins.object with metaclasses (Issues #91, #96)

  • Fix futurize’s refactoring of urllib imports (Issue #94)

  • Fix futurize --all-imports (Issue #101)

  • Fix futurize --output-dir logging (Issue #102)

  • Doc formatting fix (Issues #98, #100)

Changes in version 0.13.0 (2014-08-13)

This is mostly a clean-up release. It adds some small new compatibility features and fixes several bugs.


The following unused internal modules are now deprecated. They will be removed in a future release:

  • future.utils.encoding and future.utils.six.

(Issue #80). See here for the rationale for unbundling them.

New features

  • Docs: Add Cheat Sheet: Writing Python 2-3 compatible code from Ed Schofield’s PyConAU 2014 talk.

  • Add newint.to_bytes() and newint.from_bytes(). (Issue #85)

  • Add future.utils.raise_from as an equivalent to Py3’s raise ... from ... syntax. (Issue #86)

  • Add past.builtins.oct() function.

  • Add backports for Python 2.6 of subprocess.check_output(), itertools.combinations_with_replacement(), and functools.cmp_to_key().

Bug fixes

  • Use a private logger instead of the global logger in future.standard_library (Issue #82). This restores compatibility of the standard library hooks with flask. (Issue #79)

  • Stage 1 of futurize no longer renames next methods to __next__ (Issue #81). It still converts method calls to next(obj) correctly.

  • Prevent introduction of a second set of parentheses in print() calls in some further cases.

  • Fix isinstance checks for subclasses of future types. (Issue #89)

  • Be explicit about encoding file contents as UTF-8 in unit tests. (Issue #63) Useful for building RPMs and in other environments where LANG=C.

  • Fix for 3-argument pow(x, y, z) with newint arguments. (Thanks to @str4d.) (Issue #87)

Changes in version 0.12.4 (2014-07-18)

  • Fix upcasting behaviour of newint. (Issue #76)

Changes in version 0.12.3 (2014-06-19)

  • Add “official Python 3.4 support”: Py3.4 is now listed among the PyPI Trove classifiers and the tests now run successfully on Py3.4. (Issue #67)

  • Add backports of collections.OrderedDict and collections.Counter for Python 2.6. (Issue #52)

  • Add --version option for futurize and pasteurize scripts. (Issue #57)

  • Fix future.utils.ensure_new_type with long input. (Issue #65)

  • Remove some false alarms on checks for ambiguous fixer names with futurize -f ....

  • Testing fixes:
    • Don’t hard-code Python interpreter command in tests. (Issue #62)

    • Fix deprecated unittest usage in Py3. (Issue #62)

    • Be explicit about encoding temporary file contents as UTF-8 for when LANG=C (e.g., when building an RPM). (Issue #63)

    • All undecorated tests are now passing again on Python 2.6, 2.7, 3.3, and 3.4 (thanks to Elliott Sales de Andrade).

  • Docs:
    • Add list of fixers used by futurize. (Issue #58)

    • Add list of contributors to the Credits page.

Changes in version 0.12.2 (2014-05-25)

  • Add bytes.maketrans() method. (Issue #51)

  • Add support for Python versions between 2.7.0 and 2.7.3 (inclusive). (Issue #53)

  • Bug fix for newlist(newlist([1, 2, 3])). (Issue #50)

Changes in version 0.12.1 (2014-05-14)

  • Python 2.6 support: future.standard_library now isolates the importlib dependency to one function (import_) so the importlib backport may not be needed.

  • Doc updates

Changes in version 0.12.0 (2014-05-06)

The major new feature in this version is improvements in the support for the reorganized standard library (PEP 3108) and compatibility of the import mechanism with 3rd-party modules.

More robust standard-library import hooks

Note: backwards-incompatible change: As previously announced (see Deprecated feature: auto-installation of standard-library import hooks), the import hooks must now be enabled explicitly, as follows:

from future import standard_library
with standard_library.hooks():
    import html.parser
    import http.client

This now causes these modules to be imported from future.moves, a new package that provides wrappers over the native Python 2 standard library with the new Python 3 organization. As a consequence, the import hooks provided in future.standard_library are now fully compatible with the Requests library.

The functional interface with install_hooks() is still supported for backwards compatibility:

from future import standard_library

import html.parser
import http.client

Explicit installation of import hooks allows finer-grained control over whether they are enabled for other imported modules that provide their own Python 2/3 compatibility layer. This also improves compatibility of future with tools like py2exe.

newobject base object defines fallback Py2-compatible special methods

There is a new future.types.newobject base class (available as future.builtins.object) that can streamline Py2/3 compatible code by providing fallback Py2-compatible special methods for its subclasses. It currently provides next() and __nonzero__() as fallback methods on Py2 when its subclasses define the corresponding Py3-style __next__() and __bool__() methods.

This obviates the need to add certain compatibility hacks or decorators to the code such as the @implements_iterator decorator for classes that define a Py3-style __next__ method.

In this example, the code defines a Py3-style iterator with a __next__ method. The object class defines a next method for Python 2 that maps to __next__:

from future.builtins import object

class Upper(object):
    def __init__(self, iterable):
        self._iter = iter(iterable)
    def __next__(self):                 # note the Py3 interface
        return next(self._iter).upper()
    def __iter__(self):
        return self

assert list(Upper('hello')) == list('HELLO')

newobject defines other Py2-compatible special methods similarly: currently these include __nonzero__ (mapped to __bool__) and __long__ (mapped to __int__).

Inheriting from newobject on Python 2 is safe even if your class defines its own Python 2-style __nonzero__ and next and __long__ methods. Your custom methods will simply override those on the base class.

On Python 3, as usual, future.builtins.object simply refers to builtins.object.

past.builtins module improved

The past.builtins module is much more compatible with the corresponding builtins on Python 2; many more of the Py2 unit tests pass on Py3. For example, functions like map() and filter() now behave as they do on Py2 with with None as the first argument.

The past.builtins module has also been extended to add Py3 support for additional Py2 constructs that are not adequately handled by lib2to3 (see Issue #37). This includes new execfile() and cmp() functions. futurize now invokes imports of these functions from past.builtins.

surrogateescape error handler

The newstr type (future.builtins.str) now supports a backport of the Py3.x 'surrogateescape' error handler for preserving high-bit characters when encoding and decoding strings with unknown encodings.

newlist type

There is a new list type in future.builtins that offers .copy() and .clear() methods like the list type in Python 3.

listvalues and listitems

future.utils now contains helper functions listvalues and listitems, which provide Python 2-style list snapshotting semantics for dictionaries in both Python 2 and Python 3.

These came out of the discussion around Nick Coghlan’s now-withdrawn PEP 469.

There is no corresponding listkeys(d) function; use list(d) instead.


The number of unit tests has increased from 600 to over 800. Most of the new tests come from Python 3.3’s test suite.

Refactoring of future.standard_library.* -> future.backports

The backported standard library modules have been moved to future.backports to make the distinction clearer between these and the new future.moves package.

Backported http.server and urllib modules

Alpha versions of backports of the http.server and urllib module from Python 3.3’s standard library are now provided in future.backports.

Use them like this:

from future.backports.urllib.request import Request    # etc.
from future.backports.http import server as http_server

Or with this new interface:

from future.standard_library import import_, from_import

Request = from_import('urllib.request', 'Request', backport=True)
http = import_('http.server', backport=True)

Internal refactoring

The future.builtins.types module has been moved to future.types. Likewise, past.builtins.types has been moved to past.types. The only user-visible effect of this is to change repr(type(obj)) for instances of these types. For example:

>>> from future.builtins import bytes
>>> bytes(b'abc')
>>> type(b)

Instead of:

>>> type(b)           # prior to v0.12

Bug fixes

Many small improvements and fixes have been made across the project. Some highlights are:

  • Fixes and updates from Python 3.3.5 have been included in the backported standard library modules.

  • Scrubbing of the sys.modules cache performed by remove_hooks() (also called by the suspend_hooks and hooks context managers) is now more conservative.

  • The fix_next and fix_reduce fixers have been moved to stage 1 of futurize.

  • futurize: Shebang lines such as #!/usr/bin/env python and source code file encoding declarations like # -*- coding=utf-8 -*- are no longer occasionally displaced by from __future__ import ... statements. (Issue #10)

  • Improved compatibility with py2exe (Issue #31).

  • The future.utils.bytes_to_native_str function now returns a platform-native string object and future.utils.native_str_to_bytes returns a newbytes object on Py2. (Issue #47).

  • The backported http.client module and related modules use other new backported modules such as email. As a result they are more compliant with the Python 3.3 equivalents.

Changes in version 0.11.4 (2014-05-25)

This release contains various small improvements and fixes:

  • This release restores Python 2.6 compatibility. (Issue #42)

  • The fix_absolute_import fixer now supports Cython .pyx modules. (Issue #35)

  • Right-division with newint objects is fixed. (Issue #38)

  • The fix_dict fixer has been moved to stage2 of futurize.

  • Calls to bytes(string, encoding[, errors]) now work with encoding and errors passed as positional arguments. Previously this only worked if encoding and errors were passed as keyword arguments.

  • The 0-argument super() function now works from inside static methods such as __new__. (Issue #36)

  • future.utils.native(d) calls now work for future.builtins.dict objects.

Changes in version 0.11.3 (2014-02-27)

This release has improvements in the standard library import hooks mechanism and its compatibility with 3rd-party modules:

Improved compatibility with requests

The __exit__ function of the hooks context manager and the remove_hooks function both now remove submodules of future.standard_library from the sys.modules cache. Therefore this code is now possible on Python 2 and 3:

from future import standard_library
import http.client
import requests

data = requests.get('')

Previously, this required manually removing http and http.client from sys.modules before importing requests on Python 2.x. (Issue #19)

This change should also improve the compatibility of the standard library hooks with any other module that provides its own Python 2/3 compatibility code.

Note that the situation will improve further in version 0.12; import hooks will require an explicit function call or the hooks context manager.

Conversion scripts explicitly install import hooks

The futurize and pasteurize scripts now add an explicit call to install_hooks() to install the standard library import hooks. These scripts now add these two lines:

from future import standard_library

instead of just the first one. The next major version of future (0.12) will require the explicit call or use of the hooks context manager. This will allow finer-grained control over whether import hooks are enabled for other imported modules, such as requests, which provide their own Python 2/3 compatibility code.

futurize script no longer adds unicode_literals by default

There is a new --unicode-literals flag to futurize that adds the import:

from __future__ import unicode_literals

to the top of each converted module. Without this flag, futurize now no longer adds this import. (Issue #22)

The pasteurize script for converting from Py3 to Py2/3 still adds unicode_literals. (See the comments in Issue #22 for an explanation.)

Changes in version 0.11 (2014-01-28)

There are several major new features in version 0.11.

past package

The python-future project now provides a past package in addition to the future package. Whereas future provides improved compatibility with Python 3 code to Python 2, past provides support for using and interacting with Python 2 code from Python 3. The structure reflects that of future, with past.builtins and past.utils. There is also a new past.translation package that provides transparent translation of Python 2 code to Python 3. (See below.)

One purpose of past is to ease module-by-module upgrades to codebases from Python 2. Another is to help with enabling Python 2 libraries to support Python 3 without breaking the API they currently provide. (For example, user code may expect these libraries to pass them Python 2’s 8-bit strings, rather than Python 3’s bytes object.) A third purpose is to help migrate projects to Python 3 even if one or more dependencies are still on Python 2.

Currently past.builtins provides forward-ports of Python 2’s str and dict objects, basestring, and list-producing iterator functions. In later releases, past.builtins will be used internally by the past.translation package to help with importing and using old Python 2 modules in a Python 3 environment.

Auto-translation of Python 2 modules upon import

past provides an experimental translation package to help with importing and using old Python 2 modules in a Python 3 environment.

This is implemented using import hooks that attempt to automatically translate Python 2 modules to Python 3 syntax and semantics upon import. Use it like this:

$ pip3 install plotrique==0.2.5-7 --no-compile   # to ignore SyntaxErrors
$ python3

Then pass in a whitelist of module name prefixes to the past.translation.autotranslate() function. Example:

>>> from past.translation import autotranslate
>>> autotranslate(['plotrique'])
>>> import plotrique

This is intended to help you migrate to Python 3 without the need for all your code’s dependencies to support Python 3 yet. It should be used as a last resort; ideally Python 2-only dependencies should be ported properly to a Python 2/3 compatible codebase using a tool like futurize and the changes should be pushed to the upstream project.

For more information, see Using Python 2-only dependencies on Python 3.

Separate pasteurize script

The functionality from futurize --from3 is now in a separate script called pasteurize. Use pasteurize when converting from Python 3 code to Python 2/3 compatible source. For more information, see pasteurize: Py3 to Py2/3.


There is now a pow() function in future.builtins.misc that behaves like the Python 3 pow() function when raising a negative number to a fractional power (returning a complex number).

input() no longer disabled globally on Py2

Previous versions of future deleted the input() function from __builtin__ on Python 2 as a security measure. This was because Python 2’s input() function allows arbitrary code execution and could present a security vulnerability on Python 2 if someone expects Python 3 semantics but forgets to import input from future.builtins. This behaviour has been reverted, in the interests of broadening the compatibility of future with other Python 2 modules.

Please remember to import input from future.builtins if you use input() in a Python 2/3 compatible codebase.

Deprecated feature: auto-installation of standard-library import hooks

Previous versions of python-future installed import hooks automatically upon importing the standard_library module from future. This has been deprecated in order to improve robustness and compatibility with modules like requests that already perform their own single-source Python 2/3 compatibility.

As of v0.12, importing future.standard_library will no longer install import hooks by default. Instead, please install the import hooks explicitly as follows:

from future import standard_library

And uninstall them after your import statements using:


Note: This is a backward-incompatible change.

Internal changes

The internal future.builtins.backports module has been renamed to future.builtins.types. This will change the repr of future types but not their use.

Changes in version 0.10.2 (2014-01-11)

New context-manager interface to standard_library.hooks

There is a new context manager future.standard_library.hooks. Use it like this:

from future import standard_library
with standard_library.hooks():
    import queue
    import configserver
    from http.client import HTTPConnection
    # etc.

If not using this context manager, it is now encouraged to add an explicit call to standard_library.install_hooks() as follows:

from future import standard_library

import queue
import html
import http.client
# etc.

And to remove the hooks afterwards with:


The functions install_hooks() and remove_hooks() were previously called enable_hooks() and disable_hooks(). The old names are deprecated (but are still available as aliases).

As usual, this feature has no effect on Python 3.

Changes in version 0.10.0 (2013-12-02)

Backported dict type

future.builtins now provides a Python 2 dict subclass whose keys(), values(), and items() methods produce memory-efficient iterators. On Python 2.7, these also have the same set-like view behaviour as on Python 3. This can streamline code needing to iterate over large dictionaries. For example:

from __future__ import print_function
from future.builtins import dict, range

squares = dict({i: i**2 for i in range(10**7)})

assert not isinstance(d.items(), list)
# Because items() is memory-efficient, so is this:
square_roots = dict((i_squared, i) for (i, i_squared) in squares.items())

For more information, see dict.

Utility functions raise_ and exec_

The functions raise_with_traceback() and raise_() were added to future.utils to offer either the Python 3.x or Python 2.x behaviour for raising exceptions. Thanks to Joel Tratner for the contribution of these. future.utils.reraise() is now deprecated.

A portable exec_() function has been added to future.utils from six.


  • Fixed newint.__divmod__

  • Improved robustness of installing and removing import hooks in future.standard_library

  • v0.10.1: Fixed broken pip install future on Py3

Changes in version 0.9 (2013-11-06)

isinstance checks are supported natively with backported types

The isinstance function is no longer redefined in future.builtins to operate with the backported int, bytes and str. isinstance checks with the backported types now work correctly by default; we achieve this through overriding the __instancecheck__ method of metaclasses of the backported types.

For more information, see isinstance.

futurize: minimal imports by default

By default, the futurize script now only adds the minimal set of imports deemed necessary.

There is now an --all-imports option to the futurize script which gives the previous behaviour, which is to add all __future__ imports and from future.builtins import * imports to every module. (This even applies to an empty file.)

Looser type-checking for the backported str object

Now the future.builtins.str object behaves more like the Python 2 unicode object with regard to type-checking. This is to work around some bugs / sloppiness in the Python 2 standard library involving mixing of byte-strings and unicode strings, such as os.path.join in

future.builtins.str still raises the expected TypeError exceptions from Python 3 when attempting to mix it with future.builtins.bytes.

suspend_hooks() context manager added to future.standard_library

Pychecker (as of v0.6.1)’s attempts to import the builtins module as a way of determining whether Python 3 is running. Since this succeeds when from future import standard_library is in effect, this check does not work and pychecker sets the wrong value for its internal PY2 flag is set.

To work around this, future now provides a context manager called suspend_hooks that can be used as follows:

from future import standard_library
with standard_library.suspend_hooks():
    from pychecker.checker import Checker

Changes in version 0.8 (2013-10-28)

Python 2.6 support

future now includes support for Python 2.6.

To run the future test suite on Python 2.6, this additional package is needed:

pip install unittest2

http.server also requires the argparse package:

pip install argparse

Unused modules removed

The future.six module has been removed. future doesn’t require six (and hasn’t since version 0.3). If you need support for Python versions before 2.6, six is the best option. future and six can be installed alongside each other easily if needed.

The unused hacks module has also been removed from the source tree.

isinstance() added to future.builtins (v0.8.2)

It is now possible to use isinstance() calls normally after importing isinstance from future.builtins. On Python 2, this is specially defined to be compatible with future’s backported int, str, and bytes types, as well as handling Python 2’s int/long distinction.

The result is that code that uses isinstance to perform type-checking of ints, strings, and bytes should now work identically on Python 2 as on Python 3.

The utility functions isint, istext, and isbytes provided before for compatible type-checking across Python 2 and 3 in future.utils are now deprecated.

Summary of all changes

  • Full backports of urllib.parse and other urllib submodules are exposed by install_aliases().

  • tkinter.ttk support

  • Initial surrogateescape support

  • Additional backports: collections, http constants, etc.

  • Bug fixes

  • Bug fixes

  • Bug fixes

  • Bug fixes

  • New top-level builtins package on Py2 for cleaner imports. Equivalent to future.builtins

  • New top-level packages on Py2 with the same names as Py3 standard modules: configparser, copyreg, html, http, xmlrpc, winreg

  • Bug fixes

  • Cheat sheet for writing Python 2/3 compatible code

  • to_int and from_int methods for newbytes

  • Bug fixes

  • Add newobject and newlist types

  • Improve compatibility of import hooks with Requests, py2exe

  • No more auto-installation of import hooks by future.standard_library

  • New future.moves package

  • past.builtins improved

  • newstr.encode(..., errors='surrogateescape') supported

  • Refactoring: future.standard_library submodules -> future.backports

  • Refactoring: future.builtins.types -> future.types

  • Refactoring: past.builtins.types -> past.types

  • New listvalues and listitems functions in future.utils

  • Many bug fixes to futurize, future.builtins, etc.

  • Restore Py2.6 compatibility

  • The futurize and pasteurize scripts add an explicit call to future.standard_library.install_hooks() whenever modules affected by PEP 3108 are imported.

  • The future.builtins.bytes constructor now accepts frozenset objects as on Py3.

  • The past.translation.autotranslate feature now finds modules to import more robustly and works with Python eggs.

  • Update to requirements_py26.txt for Python 2.6. Small updates to docs and tests.

  • New past package with past.builtins and past.translation modules.

  • Improvements to stdlib hooks. New context manager: future.standard_library.hooks().

  • New raise_ and raise_with_traceback functions in future.utils.

  • New backported dict object with set-like keys, values, items

  • isinstance() hack removed in favour of __instancecheck__ on the metaclasses of the backported types

  • futurize now only adds necessary imports by default

  • Looser type-checking by future.builtins.str when combining with Py2 native byte-strings.

  • New --all-imports option to futurize

  • Fix bug with str.encode() with encoding as a non-keyword arg

  • Backported Fixes sporadic test failures with http.server (related to threading and old-style classes used in Py2.7’s

  • Move a few more safe futurize fixes from stage2 to stage1

  • Bug fixes to future.utils

  • Added Python 2.6 support

  • Removed unused modules: future.six and future.hacks

  • Removed undocumented functions from future.utils

  • Added a backported Py3-like int object (inherits from long).

  • Added utility functions for type-checking and docs about isinstance uses/alternatives.

  • Fixes and stricter type-checking for bytes and str objects

  • Added many more tests for the futurize script

  • We no longer disable obsolete Py2 builtins by default with from future.builtins import *. Use from future.builtins.disabled import * instead.

  • Added a backported Py3-like str object (inherits from Py2’s unicode)

  • Removed support for the form from future import *; use from future.builtins import * instead

  • Doc improvements

  • Add lots of docs and a Sphinx project

  • Upgraded included six module (included as future.utils.six) to v1.4.1

  • http.server module backported

  • bytes.split() and .rsplit() bugfixes

  • Added backported Py3-like bytes object

  • Various fixes

  • Added open() (from io module on Py2)

  • Improved docs

  • Added various useful compatibility functions to future.utils

  • Reorganized package: moved all builtins to future.builtins; moved all stdlib things to future.standard_library

  • Renamed python-futurize console script to futurize

  • Moved future.six to future.utils.six and pulled the most relevant definitions to future.utils.

  • More improvements to “Py3 to both” conversion ( --from3)

  • Fixed broken package setup (“package directory ‘libfuturize/tests’ does not exist”)

  • Added itertools.zip_longest

  • Updated 2to3_backcompat tests to use

  • Improved libfuturize fixers: correct order of imports; add imports only when necessary (except absolute_import currently)

  • Added python-futurize console script

  • Added itertools.filterfalse

  • Removed docs about unfinished backports (urllib etc.)

  • Removed old Py2 syntax in some files that breaks py3 install

  • Added module

  • Added UserList, UserString, UserDict classes to collections module

  • Removed int -> long mapping

  • Added backported etc. with new-style classes to fix travis-ci build problems

  • Added working html and http.client backported modules

  • Generalized import hooks to allow dotted imports

  • Added backports of urllib, html, http modules from Py3.3 stdlib using future

  • Added futurize script for automatically turning Py2 or Py3 modules into cross-platform Py3 modules

  • Renamed future.standard_library_renames to future.standard_library. (No longer just renames, but backports too.)

  • Small bug fixes to get tests passing on

  • Small bug fixes

  • Features module renamed to modified_builtins

  • New functions added: round(), input()

  • No more namespace pollution as a policy:

    from future import *

    should have no effect on Python 3. On Python 2, it only shadows the builtins; it doesn’t introduce any new names.

  • End-to-end tests with Python 2 code and 2to3 now work

  • first version with tests!

  • removed the inspect-module magic

  • initial releases. Use at your peril.