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Sunday 25 June 2017

Python package licences

How to determine the licence of your pip installed packages

Sometimes it’s handy to know the licences of your project’s dependancies. You could check each entry in requirements.txt one by one, but it’d be too easy to miss out a nested dependancy. Also, if a project has a lot of dependancies, it quickly becomes laborious. Don’t worry though, it’s easy to script, and I’ve already done it for you:

from __future__ import print_function
from collections import defaultdict
from os.path import join

# The `pkg_resources` module isn't in the standard library,
# but it's frequently available anywhere the `setuptools`
# module is (it typically comes with `pip`).
import pkg_resources

licences = defaultdict(list)

# We go over each installed package:
for package in pkg_resources.working_set:
    # Find the directory where the metadata is stored.
    info_dir = package._provider.egg_info
    if info_dir is None:
        print('No data for {}'.format(package))
    # Determine if the package is a wheel...
    is_wheel = info_dir.endswith('.dist-info')
    # ...and chose correct file.
    filename = 'METADATA' if is_wheel else 'PKG-INFO'
    filepath = join(info_dir, filename)

    # We then loop over the lines in the file...
    with open(filepath, 'r') as lines:
        for line in sorted(lines):
            # ...find the line that stores the license...
            if (line.startswith('Classifier: License :: ') or
                    line.startswith('License: ')):
                # ... and add the package to the list for it.
                license = line.rsplit(': ')[-1].strip()
            print('No data for {}'.format(package))

# Then all we have to do is print it out:
for licence, packages in licences.items():
    for package in packages:
        print('\t', package)

Note that this only works for packages where the correct information has been added to the dependancy’s setup.py.