license 0.1a3

Library that encapsulates free software licenses

license is a Python library providing some metadata about common free software licenses, such as GNU GPL, MIT and others. It is compatible with Python 3.3+ and legacy Python 2.7.

Basic usage

To get a license, you can use SPDX license identifier:

import license
mit = license.find('MIT')

Each license is a static class providing a few properties:

• id - the SPDX identifier

• name - a human readable name of the license

• rpm - license identifier used in Fedora, RHEL and CentOS RPMs

• python - PyPI classifier

• url - link to a license description or website

mit.python
'License :: OSI Approved :: MIT License'

License classes also offer a static method render() that will output the entire license text. Some variables have to be passed to it, usually name, email and optional year (current year is used when omitted).

mit.render(name='Petr Foo', email='[e-mail]')
'''The MIT License (MIT)

Copyright (c) 2015 Petr Foo <[e-mail]>

Permission is hereby granted... (snip)'''

Some licenses (such as the ones from GPL family) also have a header text, that’s supposed to be added to each source file. header() is used to render that, but be careful, if the license does not use special header, AttributeError is risen.

mit.header(name='Petr Foo', email='[e-mail]')
AttributeError: The MIT license uses no header

If you want to search the licenses by some other key, you can:

bsd = license.find_by_key('rpm', 'BSD')
bsd
[license.licenses.BSD3ClauseLicense, license.licenses.BSD2ClauseLicense]

bsd is now a list, because unlike SPDX identifiers, other keys might not always be unique. If you only need the first license with such identifier, you can pass multiple=False to find_by_key():

bsd = license.find_by_key('rpm', 'BSD', multiple=False)
bsd
license.licenses.BSD3ClauseLicense

If such license is not found, you’ll get KeyError instead, the same as with regular find().

In case you would like to perform a lot of searches by some key, you can build and index, which should (in theory) make the searches faster (no measurements have been performed).

license.build_index('rpm')

In case you want to get rid of an index, use license.delete_index(key). It is safe to call it even if the index does not exist.

It is also possible to use find_by_function() to find licenses that match a certain expression. The function should accept one argument (the license class) and return True if the license is supposed to be in the results:

osi = license.find_by_function(lambda l: l.python.startswith('License :: OSI Approved :: '))

Again, it returns a list and has multiple argument to change that.

In case a simple function is not enough, you can iterate over all the license with license.iter():

for cls in license.iter():
    # do something

Adding licenses

The current license list is in no way much extensive, so maybe your favorite license is not in there. If you wish to change that, add the license to license/licenses.py and a template(s) to license/templates, and send a pull request on GitHub. See the current licenses to learn how to do it. A license class looks like this:

class AGPLv3LaterLicense(license.base.License):
    '''
    GNU Affero General Public License v3.0 or later
    '''
    id = 'AGPL-3.0+'
    rpm = 'AGPLv3+'
    python = 'License :: OSI Approved :: GNU Affero General Public License v3 or later (AGPLv3+)'
    url = 'http://www.gnu.org/licenses/agpl-3.0.html'

One license can inherit from other and omit the keys that are equal. Note that the docstring is important and it is used as name property. License template is named as id, header template is named with __header suffix.

If you wish to add custom licenses in your code, you can do that as well. If you won’t use render() or header(), the thing is simple. Just define such class anywhere and call license.register() on it.

However, if you would then call render() or header(), the template would hove not been found. In that case, you have to create a Custom Base License with a jinja2 template loader.

CustomBaseLicense = license.base.custom_license_base_class(loader=jinja2.FileSystemLoader('path/to/templates'))

class CustomLicense(CustomBaseLicense):
    ...

license.register(CustomLicense)

The loader can be any valid jinja2 loader. If you wish to register multiple classes at once, you can use license.autoregister() that will register all classes present in given module. You will not want to register your CustomBaseLicense, so you’ll pass it in the ignore argument.

license.autoregister(sys.modules[__name__], ignore=[CustomBaseLicense])

Note that if you add custom licenses and use license.build_index(), you want to build the index after registering them. Calling build_index() multiple times is safe.

(Possibly) Frequently Asked Questions

Why are licenses represented as subclasses and not instances of License?

This way, it is easier to inherit data between multiple licenses. The definition of classes is easier maintainable and readable.

Isn’t license a reserved name?

Yes, it is, it prints the Python’s license. Possibly something you would only use in an interactive Python console. By importing this library, you are overriding it. We could have named the library with something cool and unique, such as licenraptor, but we wanted to make the name as easy as possible. In case you don’t like this, you can always do import license as somethignelse.

Aren’t there already Python tools that can render license texts?

Yes, they are. However all of them are command line utilities and provide no API for Python programmers.

• choosealicense-cli

• licenser

• licen

• garnish