Python Package Versions

Python packages should (must?) have a version. It would be best if that version string was a semantic version, but this article is not about how your version string should look like. It's about how to have a consistent version string on PyPI and accessible via [yourpackage].__version__ - and preferably make sure it is the same as used in git tag.

setup.py should have the version string in the setup function:

from setuptools import setup

setup(version=__version__)

Having this makes sure that the correct version is on PyPI and you can work with that version via pip (e.g. pip freeze). But if you import the package via import [yourpackage] and execute [yourpackage].__version__ it might not be present. Also, if you have a command line application, you have to make sure yourself that there is a --version command. And you definitely should do that; it comes in handy.

There is an official guide for "single-sourcing the package version". So it is a know problem with known solutions. I only wrap them up here.

The Manual Approach

setup.py:

from setuptools import setup

setup(version='0.1.2')

[yourpackage]/init.py:

__version__ = '0.1.2'

Positive:

• No new dependencies
• It is super simple to understand

Negative:

• You can easily get inconsistencies by forgetting something

Version Python File

setup.py:

from setuptools import setup

exec(open('[yourpackage]/_version.py').read())

setup(version=__version__)

[yourpackage]/init.py:

from [yourpackage]._version import __version__

[yourpackage]/_version.py:

__version__ = '0.1.2'

Positive:

• No new dependencies
• Relatively simple
• Consistent

Negative:

• You use exec, about which linters complain as it is a security risk if used wrong.
• mypy cannot know that the __version__ variable is set in the setup.py. It will give error: Name '__version__' is not defined.

Version Text File

Similar to the solution above, we use a text file which only contains the version string.

setup.py:

from setuptools import setup

def read(file_name):
    """Read a text file and return the content as a string."""
    with io.open(os.path.join(os.path.dirname(__file__), file_name),
                 encoding='utf-8') as f:
        return f.read()

setup(version=read('[yourpackage]/version.txt'))

[yourpackage]/init.py:

from [yourpackage]._version import __version__

[yourpackage]/_version.py:

__version__ = '0.1.2'

Reading setup.py

This approach is so bad that I don't want to post an example here. The idea is that you can have the version in the setup(version='fooversion') and read that within the package to set the __version__.

Reasons why I strongly suggest not to do so:

• Your package source could be simply copied, not installed. For example, if things run on AWS Lambda. In this case, there is not setup.py file. So all solutions with this break.
• You have to write rather complex parsers to be robust to changes in setup.py

External Build Tools

There are bumpversion, changes and zest.releaser. I don't have experience with those tools, but from a very quick first look I don't think they the first two look reliable enough to give them a try. And zest.releaser looks a bit complicated.

Package import

setup.py:

from setuptools import setup

import [yourpackage]

setup(version=[yourpackage].__version__))

[yourpackage]/init.py:

[yourpackage]._version = '0.1.2'

Positive:

• No new dependencies
• Very simple simple
• Consistent

Negative:

• Fails, if you import a dependency in the __init__.py.

Version Control Integration

You can use setuptools_scm and do the following:

setup.py:

from setuptools import setup

setup(
    ...,
    use_scm_version=True,
    setup_requires=['setuptools_scm'],
    ...,
)

[yourpackage]/init.py:

from pkg_resources import get_distribution, DistributionNotFound
try:
    __version__ = get_distribution(__name__).version
except DistributionNotFound:
    # package is not installed
    pass

Positive:

• git tags: You might have to / be able to use git tags to keep consistent versions. I'm not sure if this is the case, though.

Negative:

• Your package source could be simply copied, not installed. For example, if things run on AWS Lambda. In this case, there is not setup.py file. So all solutions with this break.

Reading Version String Management in Python: Introducing python-versioneer, I want to highlight some parts:

Thinking about how I use git these days, I realized that I want my release process to have one step: “git tag” (well, and a “git push” to tell the world about it). Everything else should be automated: building tarballs, uploading them to a release server, updating a web page, sending an announcement email, pypi registration, etc. What really matters is the release manager making the decision to bless some well-tested revision id with a public name of some sort.

What others do

See also

• Brian Warner: Version String Management in Python: Introducing python-versioneer