pasteurize: Py3 to Py2/3

Running pasteurize -w mypy3module.py turns this Python 3 code:

import configparser
import copyreg

class Blah:
    pass
print('Hello', end=None)

into this code which runs on both Py2 and Py3:

from __future__ import print_function
from future import standard_library
standard_library.install_hooks()

import configparser
import copyreg

class Blah(object):
    pass
print('Hello', end=None)

Notice that both futurize and pasteurize create explicit new-style classes that inherit from object on both Python versions, and both refer to stdlib modules (as well as builtins) under their Py3 names.

Note also that the configparser module is a special case; there is a full backport available on PyPI (https://pypi.org/project/configparser/), so, as of v0.16.0, python-future no longer provides a configparser package alias. To use the resulting code on Py2, install the configparser backport with pip install configparser or by adding it to your requirements.txt file.

pasteurize also handles the following Python 3 features:

• keyword-only arguments

• metaclasses (using with_metaclass())

• extended tuple unpacking (PEP 3132)

To handle function annotations (PEP 3107), see Function annotations.