Specifying Your Project’s Version

Setuptools can work well with most versioning schemes. Over the years, setuptools has tried to closely follow the PEP 440 scheme, but it also supports legacy versions. There are, however, a few special things to watch out for, in order to ensure that setuptools and other tools can always tell what version of your package is newer than another version. Knowing these things will also help you correctly specify what versions of other projects your project depends on.

A version consists of an alternating series of release numbers and pre-release or post-release tags. A release number is a series of digits punctuated by dots, such as 2.4 or 0.5. Each series of digits is treated numerically, so releases 2.1 and 2.1.0 are different ways to spell the same release number, denoting the first subrelease of release 2. But 2.10 is the tenth subrelease of release 2, and so is a different and newer release from 2.1 or 2.1.0. Leading zeros within a series of digits are also ignored, so 2.01 is the same as 2.1, and different from 2.0.1.

Following a release number, you can have either a pre-release or post-release tag. Pre-release tags make a version be considered older than the version they are appended to. So, revision 2.4 is newer than release candidate 2.4rc1, which in turn is newer than beta release 2.4b1 or alpha release 2.4a1. Postrelease tags make a version be considered newer than the version they are appended to. So, revisions like 2.4.post1 are newer than 2.4, but older than 2.4.1 (which has a higher release number).

In the case of legacy versions (for example, 2.4pl1), they are considered older than non-legacy versions. Taking that in count, a revision 2.4pl1 is older than 2.4. Note that 2.4pl1 is not PEP 440-compliant.

A pre-release tag is a series of letters that are alphabetically before “final”. Some examples of prerelease tags would include alpha, beta, a, c, dev, and so on. You do not have to place a dot or dash before the prerelease tag if it’s immediately after a number, but it’s okay to do so if you prefer. Thus, 2.4c1 and 2.4.c1 and 2.4-c1 all represent release candidate 1 of version 2.4, and are treated as identical by setuptools. Note that only a, b, and rc are PEP 440-compliant pre-release tags.

In addition, there are three special prerelease tags that are treated as if they were rc: c, pre, and preview. So, version 2.4c1, 2.4pre1 and 2.4preview1 are all the exact same version as 2.4rc1, and are treated as identical by setuptools.

A post-release tag is the string .post, followed by a non-negative integer value. Post-release tags are generally used to separate patch numbers, port numbers, build numbers, revision numbers, or date stamps from the release number. For example, the version 2.4.post1263 might denote Subversion revision 1263 of a post-release patch of version 2.4. Or you might use 2.4.post20051127 to denote a date-stamped post-release. Legacy post-release tags could be either a series of letters that are alphabetically greater than or equal to “final”, or a dash (-) - for example 2.4-r1263 or 2.4-20051127.

Notice that after each legacy pre or post-release tag, you are free to place another release number, followed again by more pre- or post-release tags. For example, 0.6a9.dev41475 could denote Subversion revision 41475 of the in-development version of the ninth alpha of release 0.6. Notice that dev is a pre-release tag, so this version is a lower version number than 0.6a9, which would be the actual ninth alpha of release 0.6. But the 41475 is a post-release tag, so this version is newer than 0.6a9.dev.

For the most part, setuptools’ interpretation of version numbers is intuitive, but here are a few tips that will keep you out of trouble in the corner cases:

  • Don’t stick adjoining pre-release tags together without a dot or number between them. Version 1.9adev is the adev prerelease of 1.9, not a development pre-release of 1.9a. Use .dev instead, as in 1.9a.dev, or separate the prerelease tags with a number, as in 1.9a0dev. 1.9a.dev, 1.9a0dev, and even 1.9a0.dev0 are identical versions from setuptools’ point of view, so you can use whatever scheme you prefer. Of these examples, only 1.9a0.dev0 is PEP 440-compliant.

  • If you want to be certain that your chosen numbering scheme works the way you think it will, you can use the pkg_resources.parse_version() function to compare different version numbers:

    >>> from pkg_resources import parse_version
    >>> parse_version("1.9.a.dev") == parse_version("1.9a0dev")
    >>> parse_version("2.1-rc2") < parse_version("2.1")
    >>> parse_version("0.6a9dev-r41475") < parse_version("0.6a9")

Once you’ve decided on a version numbering scheme for your project, you can have setuptools automatically tag your in-development releases with various pre- or post-release tags. See the following section for more details.

Tagging and “Daily Build” or “Snapshot” Releases


Please note that running python setup.py ... directly is no longer considered a good practice and that in the future the commands egg_info and rotate will be deprecated.

As a result, the instructions and information presented in this section should be considered transitional while setuptools don’t provide a mechanism for tagging releases.

Meanwhile, if you can also consider using setuptools-scm to achieve similar objectives.

When a set of related projects are under development, it may be important to track finer-grained version increments than you would normally use for e.g. “stable” releases. While stable releases might be measured in dotted numbers with alpha/beta/etc. status codes, development versions of a project often need to be tracked by revision or build number or even build date. This is especially true when projects in development need to refer to one another, and therefore may literally need an up-to-the-minute version of something!

To support these scenarios, setuptools allows you to “tag” your source and egg distributions by adding one or more of the following to the project’s “official” version identifier:

  • A manually-specified pre-release tag, such as “build” or “dev”, or a manually-specified post-release tag, such as a build or revision number (--tag-build=STRING, -bSTRING)

  • An 8-character representation of the build date (--tag-date, -d), as a postrelease tag

You can add these tags by adding egg_info and the desired options to the command line ahead of the sdist or bdist commands that you want to generate a daily build or snapshot for. See the section below on the egg_info command for more details.

(Also, before you release your project, be sure to see the section on Specifying Your Project’s Version for more information about how pre- and post-release tags affect how version numbers are interpreted. This is important in order to make sure that dependency processing tools will know which versions of your project are newer than others).

Finally, if you are creating builds frequently, and either building them in a downloadable location or are copying them to a distribution server, you should probably also check out the rotate command, which lets you automatically delete all but the N most-recently-modified distributions matching a glob pattern. So, you can use a command line like:

setup.py egg_info -rbDEV bdist_egg rotate -m.egg -k3

to build an egg whose version info includes “DEV-rNNNN” (where NNNN is the most recent Subversion revision that affected the source tree), and then delete any egg files from the distribution directory except for the three that were built most recently.

If you have to manage automated builds for multiple packages, each with different tagging and rotation policies, you may also want to check out the alias command, which would let each package define an alias like daily that would perform the necessary tag, build, and rotate commands. Then, a simpler script or cron job could just run setup.py daily in each project directory. (And, you could also define sitewide or per-user default versions of the daily alias, so that projects that didn’t define their own would use the appropriate defaults.)

Making “Official” (Non-Snapshot) Releases

When you make an official release, creating source or binary distributions, you will need to override the tag settings from setup.cfg, so that you don’t end up registering versions like foobar-0.7a1.dev-r34832. This is easy to do if you are developing on the trunk and using tags or branches for your releases - just make the change to setup.cfg after branching or tagging the release, so the trunk will still produce development snapshots.

Alternately, if you are not branching for releases, you can override the default version options on the command line, using something like:

setup.py egg_info -Db "" sdist bdist_egg

The first part of this command (egg_info -Db "") will override the configured tag information, before creating source and binary eggs. Thus, these commands will use the plain version from your setup.py, without adding the build designation string.

Of course, if you will be doing this a lot, you may wish to create a personal alias for this operation, e.g.:

setup.py alias -u release egg_info -Db ""

You can then use it like this:

setup.py release sdist bdist_egg

Or of course you can create more elaborate aliases that do all of the above. See the sections below on the egg_info and alias commands for more ideas.