Version handling

Where does the version come from?

A version number is essentially what zest.releaser cannot do without. A version number can come from three different locations:

  • The file. Two styles are supported:

    version = '1.0'
    def setup(

    and also:

    def setup(
  • If no is found, zest.releaser looks for a version.txt file. It should contain just a version number (a newline at the end is OK).

    Originally the version.txt was only meant to support really old and ancient Plone packages, but it turned out to be quite useful for non-Python packages, too. A completely static website, for instance, that you do want to release and that you do want a changelog for.

  • A __version__ attribute in a Python file. You need to tell zest.releaser which Python file by adding (or updating) the setup.cfg file next to the You need a [zest.releaser] header and a python-file-with-version option:

    python-file-with-version = mypackage/

    Because you need to configure this explicitly, this option takes precedence over any or version.txt file.

Where is the version number being set?

Of those three locations where the version can come from, only the first one found is also set to the new value again. Zest.releaser assumes that there’s only one location.

According to PEP 396, the version should have one source and all the others should be derived from it.

Using the version number in and as __version__

Here are opinionated suggestions from the zest.releaser main authors about how to use the version information. For some other ideas, see the zest.releaser issue 37 discussion.

  • The version in the is the real version.

  • Add a __version__ attribute in your main module. Often this will be an Set this version attribute with pkg_resources, which is automatically installed as part of setuptools/distribute. Here’s the code from zest/releaser/

    import pkg_resources
    __version__ = pkg_resources.get_distribution("zest.releaser").version

    This way you can do:

    >>> import zest.releaser
    >>> zest.releaser.__version__
  • If you use Sphinx for generating your documentation, use the same pkg_resources trick to set the version and release in your Sphinx’s See zest.releaser’s