Clean single-source support for Python 3 and 2
Project description
Overview
future is the missing compatibility layer between Python 3 and Python 2. It allows you to maintain a single, clean Python 3.x-compatible codebase with minimal cruft and run it easily on Python 2 without further modification.
Features
backports or remappings for 15 builtins with different semantics on Py3 versus Py2
supports the reorganized Py3 standard library interface
220+ unit tests
clean on Py3: future imports and decorators have no effect on Py3 (and no namespace pollution)
futurize script for automatic conversion from either Py2 or Py3 to a clean single-source codebase compatible with both Py3 and Py2
a consistent set of utility functions and decorators selected from Py2/3 compatibility interfaces from projects like six, IPython, Jinja2, Django, and Pandas.
Code examples
future is designed to be imported at the top of each Python module together with Python’s built-in __future__ module like this:
from __future__ import (absolute_import, division, print_function, unicode_literals) from future import standard_library from future.builtins import *
followed by standard Python 3 code. The imports allow this code to run unchanged on Python 3 and Python 2.7.
For example, after these imports, this code runs identically on Python 3 and 2.7:
# Support for renamed standard library modules via import hooks from http.client import HttpConnection from itertools import filterfalse import html.parser import queue # Backported Py3 bytes object b = bytes(b'ABCD') assert list(b) == [65, 66, 67, 68] assert repr(b) == "b'ABCD'" # These raise TypeErrors: # b + u'EFGH' # bytes(b',').join([u'Fred', u'Bill']) # Extra arguments for the open() function f = open('japanese.txt', encoding='utf-8', errors='replace') # New iterable range object with slicing support for i in range(10**15)[:10]: pass # Other iterators: map, zip, filter 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() replaces Py2's raw_input() (with no eval()): name = input('What is your name? ') print('Hello ' + name)
Documentation
Credits
- Author:
Ed Schofield
- Sponsor:
Python Charmers Pty Ltd, Australia, and Python Charmers Pte Ltd, Singapore. http://pythoncharmers.com
- Others:
The backported super() and range() functions are derived from Ryan Kelly’s magicsuper module and Dan Crosta’s xrange module.
The futurize script uses lib2to3, lib3to2, and parts of Armin Ronacher’s python-modernize code.
The python_2_unicode_compatible decorator is from Django. The implements_iterator and with_metaclass decorators are from Jinja2.
future incorporates the six module by Benjamin Peterson as future.utils.six.
Documentation is generated using sphinx using an adaptation of Armin Ronacher’s stylesheets from Jinja2.
Licensing
Copyright 2013 Python Charmers Pty Ltd, Australia. The software is distributed under an MIT licence. See LICENSE.txt.
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