Wait… Why? What??

PEP440 codifies a version scheme for Python packages. This setuptools extension will generate Developmental Release and Local Version Label segments that identify the revision that is being built. PEP440 defines the following format for Python package versions:

version         = [epoch "!"] public-version ["+" local-version]
epoch           = digit+
public-version  = release-segment [pre-segment] [post-segment] [dev-segment]
local-version   = (letter | digit)+ ["." (letter|digit)+]
release-segment = digit+ ("." digit+)*
pre-segment     = "a" digit+ | "b" digit+ | "rc" digit+
post-segment    = ".post" digit+
dev-segment     = ".dev" digit+

It also recommends that package indecies only accept final releases which are defined as having a version that consists of only a release segment and an optional epoch. So why did I go through all of the trouble to create an extension for managing versions that should not be submitted to a package index? If you develop Python packages that are used inside the walls of a business, then you probably know exactly why – using a local Python Package Index that holds non-public packages is commonplace. It is also common to stage pre-release packages and builds from a CI server in an internal index. This is where this extension comes into play. It provides a consistent way to manage package versions throughout all stages of development.

Let’s look at the state of this project as I am writing this document. The git history looks like the following:

* 3fdc192 - (HEAD, origin/initial-implementation, initial-implementation)
###### 9 more commits here
* 7ca1fd2 - (origin/master, master)
*   87d944e - Merge pull request #1 from dave-shawley/reorg (6 days ago)
|\
| * 04d0cca - (origin/reorg, reorg)
| ###### 9 more commits here
|/
* bd7ad3c - (tag: 0.0.0) SYN (4 months ago)

When I run setup.py git_version it sets the version to 0.0.0.post1.dev11. The 0.0.0 portion is the release segment that is passed to the setup function in setup.py. The extension finds that tag in the history and counts the number of merges that have occurred since that tag – this value becomes the post version segment. In this case there has only been a single merge. Then it counts the number of commits since the last merge occurred – this value becomes the development version segment.

How?

The easiest way to use this extension is to install it into your build environment and then use it from the command line when you generate and upload your distribution.

1. pip install setupext-gitversion into your build environment

2. Add the following lines to your setup.cfg:

[git_version]
version-file = LOCAL-VERSION

3. Add the following line to your MANIFEST.in:

   include LOCAL-VERSION

4. Modify your setup.py to append the contents of LOCAL-VERSION to your version keyword:

   version_suffix = ''
   try:
      with open('LOCAL-VERSION') as f:
         version_suffix = f.readline().strip()
   except IOError:
      pass
   
   setup(
      # normal keywords
      version='1.2.3' + version_suffix,
   )

   Where 1.2.3 is the tag of the last release package.

5. Add git_version to your upload or distribution generation command. You want to use something like the following:

   setup.py git_version sdist upload
   setup.py git_version bdist_egg upload

And that’s it. That will embed SCM information into your package when your build a distribution. It is also smart enough to generate an empty suffix for a build from a tagged commit.

Ok… Where?