past (original) (raw)

past is a package to aid with Python 2/3 compatibility. Whereas futurecontains backports of Python 3 constructs to Python 2, past provides implementations of some Python 2 constructs in Python 3. It is intended to be used sparingly, as a way of running old Python 2 code from Python 3 until it is ported properly.

Potential uses for libraries:

as a step in porting a Python 2 codebase to Python 3 (e.g. with the futurize script)
to provide Python 3 support for previously Python 2-only libraries with the same APIs as on Python 2 – particularly with regard to 8-bit strings (thepast.builtins.str type).
to aid in providing minimal-effort Python 3 support for applications using libraries that do not yet wish to upgrade their code properly to Python 3, or wish to upgrade it gradually to Python 3 style.

To install past, use:

$ pip install future

Here are some examples that run identically on Python 3 and 2:

from past.builtins import (str as oldstr, range, reduce, raw_input, xrange)

philosopher = oldstr(u'孔子'.encode('utf-8'))

This now behaves like a Py2 byte-string on both Py2 and Py3.
For example, indexing returns a Python 2-like string object, not
an integer:
philosopher[0] 'å' type(philosopher[0]) <past.builtins.oldstr>

The div() function behaves like Python 2's / operator
without "from future import division"
from past.utils import div div(3, 2) # like 3/2 in Py2 0 div(3, 2.0) # like 3/2.0 in Py2 1.5

List-producing versions of range, reduce, map, filter
from past.builtins import range, reduce range(10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) 15

Other functions removed in Python 3 are resurrected ...
from past.builtins import execfile execfile('myfile.py')

from past.builtins import raw_input name = raw_input('What is your name? ') What is your name? [cursor]

from past.builtins import reload reload(mymodule) # equivalent to imp.reload(mymodule) in Python 3

from past.builtins import xrange for i in xrange(10): ... pass

It also provides experimental import hooks so you can import and run Python 2 modules from Python 3:

from past import autotranslate autotranslate('mypy2module')

import mypy2module

Documentation

See http://python-future.org.

Credits

Author:

Ed Schofield

Sponsor:

Python Charmers Pty Ltd, Australia: http://pythoncharmers.com

past (original) (raw)

This now behaves like a Py2 byte-string on both Py2 and Py3.

For example, indexing returns a Python 2-like string object, not

an integer:

The div() function behaves like Python 2's / operator

without "from future import division"

List-producing versions of range, reduce, map, filter

Other functions removed in Python 3 are resurrected ...

Documentation

Credits

Licensing