Skip to main content

Clean single-source support for Python 3 and 2

Project description

The future module helps run Python 3.x-compatible code under Python 2 with minimal code cruft.

The goal is to allow you to write clean, modern, forward-compatible Python 3 code today and to run it with minimal effort under Python 2 alongside a Python 2 stack that may contain dependencies that have not yet been ported to Python 3.

It is designed to be used as follows:

from __future__ import (division, absolute_import, print_function,
                        unicode_literals)
from future import *

followed by clean Python 3 code (with a few restrictions) that can run unchanged on Python 2.7.

On Python 3, the from future import * line has no effect (i.e. zero namespace pollution.) On Python 2 it shadows builtins to provide the Python 3 semantics. (See below for the explicit import form.)

After the imports, this code runs identically on Python 3 and 2:

# New iterable range object with slicing support
for i in range(10**11)[:10]:
    pass

# Other common iterators: map, reduce, zip
my_iter = zip(range(3), ['a', 'b', 'c'])
assert my_iter != list(my_iter)

# New simpler super() function:
class VerboseList(list):
    def append(self, item):
        print('Adding an item')
        super().append(item)

# These raise NameErrors:
# apply(), cmp(), coerce(), reduce(), xrange(), etc.

# This identity is restored. This is normally valid on Py3 and Py2, but
# 'from __future__ import unicode_literals' breaks it on Py2:
assert isinstance('happy', str)

# The round() function behaves as it does in Python 3, using "Banker's
# Rounding" to the nearest even last digit:
assert round(0.1250, 2) == 0.12

# input() is now safe (no eval()):
name = input('What is your name? ')
print('Hello ' + name)

future also supports the standard library reorganization (PEP 3108) via import hooks, allowing standard library modules to be accessed under their Python 3 names and locations:

from future import standard_library

import socketserver
import queue
import configparser
import test.support
from collections import UserList
# and other moved modules and definitions

It also includes experimental backports for three stdlib packages from Py3 that were heavily refactored versus Py2:

import html, html.entities, html.parser
import http, http.server, http.client, http.cookies, http.cookiejar
import urllib, urllib.parse, urllib.request, urllib.error

Warning: currently only html.* and http.client pass their test suites.

Explicit imports

If you prefer explicit imports, the explicit equivalent of the from future import * line above is:

from future.common_iterators import zip, map, filter
from future.builtins import ascii, oct, hex, chr
from future.modified_builtins import (range, super, round, input)
from future.disable_obsolete_builtins import (apply, cmp, coerce,
        execfile, file, long, raw_input, reduce, reload, unicode,
        xrange, StandardError)
from future.str_is_unicode import str

But please note that the API is still evolving rapidly.

See the docstrings for each of these modules for more info:

- future.standard_library
- future.common_iterators
- future.builtins
- future.modified_builtins
- future.disable_obsolete_builtins
- future.str_as_unicode

Automatic conversion

An experimental script called futurize.py is included to aid in making either Python 2 code or Python 3 code compatible with both platforms using the future module. See https://github.com/edschofield/python-future#automatic-conversion.

Credits

Author:Ed Schofield
Sponsor:Python Charmers Pty Ltd, Australia, and Python Charmers Pte Ltd, Singapore. http://pythoncharmers.com
Others:The super() and range() functions are derived from Ryan Kelly’s magicsuper module and Dan Crosta’s xrange module. The python_2_unicode_compatible decorator is from django.utils.encoding. The fix_metaclass 2to3 fixer (from Armin Ronacher’s python-modernize) was authored by Jack Diederich and Daniel Neuhaeuser.

Licensing

Copyright 2013 Python Charmers Pty Ltd, Australia. The software is distributed under an MIT licence. See LICENSE.txt.

Project details


Release history Release notifications

History Node

0.16.0

History Node

0.15.2

History Node

0.15.1

History Node

0.15.0

History Node

0.14.3

History Node

0.14.2

History Node

0.14.1

History Node

0.14.0

History Node

0.13.1

History Node

0.13.0

History Node

0.12.4

History Node

0.12.3

History Node

0.12.2

History Node

0.12.1

History Node

0.12.0

History Node

0.11.4

History Node

0.11.3

History Node

0.11.2

History Node

0.11.1

History Node

0.11.0

History Node

0.10.2

History Node

0.10.1

History Node

0.10.0

History Node

0.9.0

History Node

0.8.2

History Node

0.8.1

History Node

0.8.0

History Node

0.7.0

History Node

0.6.0

History Node

0.5.2

History Node

0.5.1

History Node

0.5.0

History Node

0.4.1

History Node

0.4.0

History Node

0.3.5

History Node

0.3.4

History Node

0.3.3

History Node

0.3.2

This version
History Node

0.3.1

History Node

0.3.0

History Node

0.2.0

History Node

0.1.0

History Node

0.0.3

History Node

0.0.2

History Node

0.0.1

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, size & hash SHA256 hash help File type Python version Upload date
future-0.3.1.tar.gz (222.5 kB) Copy SHA256 hash SHA256 Source None Aug 4, 2013

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging CloudAMQP CloudAMQP RabbitMQ AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page