caniusepython3 3.0.0

Command-line/Web Usage

You can specify your dependencies in multiple ways:

caniusepython3 -r requirements.txt test-requirement.txt
caniusepython3 -m PKG-INFO
caniusepython3 -p numpy scipy ipython
# If your project's setup.py uses setuptools
# (note that setup_requires can't be checked) ...
python setup.py caniusepython3

The output of the script will tell you how many (implicit) dependencies you need to transition to Python 3 in order to allow you to make the same transition. It will also list what projects have no dependencies blocking their transition so you can ask them to start a port to Python 3.

If you prefer a web interface you can use https://caniusepython3.com by Jannis Leidel.

Integrating With Your Tests

If you want to check for Python 3 availability as part of your tests, you can use caniusepython3.check():

def check(requirements_paths=[], metadata=[], projects=[]):
    """Return True if all of the specified dependencies have been ported to Python 3.

    The requirements_paths argument takes a sequence of file paths to
    requirements files. The 'metadata' argument takes a sequence of strings
    representing metadata. The 'projects' argument takes a sequence of project
    names.

    Any project that is not listed on PyPI will be considered ported.
    """

You can then integrate it into your tests like so:

import unittest
import caniusepython3

class DependenciesOnPython3(unittest.TestCase):
  def test_dependencies(self):
    # Will begin to fail when dependencies are no longer blocking you
    # from using Python 3.
    self.assertFalse(caniusepython3.check(projects=['ipython']))

For the change log, how to tell if a project has been ported, as well as help on how to port a project, please see the project website.

Extending pylint --py3k

In Pylint 1.4, a --py3k option was added to the linting tool to turn on checks for Python 2/3 incompatibilities (all other checks are turned off). While great, those checks are a little conservative in order to always be accurate. To fill out those checks with stricter – albeit potentially inaccurate – checkers, caniusepython3.pylint_checker exists. On top of everything pylint --py3k already checks for, it adds checks for:

1. Uses of filter() (returns an interator in Python 3)

2. Uses of map() (returns an iterator in Python 3)

3. Uses of open() (in Python3, open() is actually io.open())

4. Uses of range() (returns an iterator in Python 3)

5. Uses of zip() (returns an iterator in Python 3)

6. String literals that do not have a b/u prefix or from __future__ import unicode_literals

If you wish to use the checker with Pylint, you can add it to your Pylint configuration file, e.g.:

[MASTER]
load-plugins=caniusepython3.pylint_checker

Secret, bonus feature

If you would like to use a different name for the script and setuptools command then set the environment variable CIU_ALT_NAME to what you would like the alternative name to be. Reddit suggests icanhazpython3.