The Versioneer

• like a rocketeer, but for versions!
• https://github.com/python-versioneer/python-versioneer
• Brian Warner
• License: Public Domain
• Compatible with: Python 3.6, 3.7, 3.8, and pypy3
• 
• 

This is a tool for managing a recorded version number in distutils-based python projects. The goal is to remove the tedious and error-prone "update the embedded version string" step from your release process. Making a new release should be as easy as recording a new tag in your version-control system, and maybe making new tarballs.

Quick Install

• pip install versioneer to somewhere in your $PATH
• add a [versioneer] section to your setup.cfg (see Install)
• run versioneer install in your source tree, commit the results
• Verify version information with python setup.py version

Version Identifiers

Source trees come from a variety of places:

• a version-control system checkout (mostly used by developers)
• a nightly tarball, produced by build automation
• a snapshot tarball, produced by a web-based VCS browser, like github's "tarball from tag" feature
• a release tarball, produced by "setup.py sdist", distributed through PyPI

Within each source tree, the version identifier (either a string or a number, this tool is format-agnostic) can come from a variety of places:

• ask the VCS tool itself, e.g. "git describe" (for checkouts), which knows about recent "tags" and an absolute revision-id
• the name of the directory into which the tarball was unpacked
• an expanded VCS keyword ($Id$, etc)
• a _version.py created by some earlier build step

For released software, the version identifier is closely related to a VCS tag. Some projects use tag names that include more than just the version string (e.g. "myproject-1.2" instead of just "1.2"), in which case the tool needs to strip the tag prefix to extract the version identifier. For unreleased software (between tags), the version identifier should provide enough information to help developers recreate the same tree, while also giving them an idea of roughly how old the tree is (after version 1.2, before version 1.3). Many VCS systems can report a description that captures this, for example git describe --tags --dirty --always reports things like "0.7-1-g574ab98-dirty" to indicate that the checkout is one revision past the 0.7 tag, has a unique revision id of "574ab98", and is "dirty" (it has uncommitted changes).

The version identifier is used for multiple purposes:

• to allow the module to self-identify its version: myproject.__version__
• to choose a name and prefix for a 'setup.py sdist' tarball

Theory of Operation

Versioneer works by adding a special _version.py file into your source tree, where your __init__.py can import it. This _version.py knows how to dynamically ask the VCS tool for version information at import time.

_version.py also contains $Revision$ markers, and the installation process marks _version.py to have this marker rewritten with a tag name during the git archive command. As a result, generated tarballs will contain enough information to get the proper version.

To allow setup.py to compute a version too, a versioneer.py is added to the top level of your source tree, next to setup.py and the setup.cfg that configures it. This overrides several distutils/setuptools commands to compute the version when invoked, and changes setup.py build and setup.py sdist to replace _version.py with a small static file that contains just the generated version data.

Installation

See INSTALL.md for detailed installation instructions.

Version-String Flavors

Code which uses Versioneer can learn about its version string at runtime by importing _version from your main __init__.py file and running the get_versions() function. From the "outside" (e.g. in setup.py), you can import the top-level versioneer.py and run get_versions().

Both functions return a dictionary with different flavors of version information:

• ['version']: A condensed version string, rendered using the selected style. This is the most commonly used value for the project's version string. The default "pep440" style yields strings like 0.11, 0.11+2.g1076c97, or 0.11+2.g1076c97.dirty. See the "Styles" section below for alternative styles.

• ['full-revisionid']: detailed revision identifier. For Git, this is the full SHA1 commit id, e.g. "1076c978a8d3cfc70f408fe5974aa6c092c949ac".

• ['date']: Date and time of the latest HEAD commit. For Git, it is the commit date in ISO 8601 format. This will be None if the date is not available.

• ['dirty']: a boolean, True if the tree has uncommitted changes. Note that this is only accurate if run in a VCS checkout, otherwise it is likely to be False or None

• ['error']: if the version string could not be computed, this will be set to a string describing the problem, otherwise it will be None. It may be useful to throw an exception in setup.py if this is set, to avoid e.g. creating tarballs with a version string of "unknown".

Some variants are more useful than others. Including full-revisionid in a bug report should allow developers to reconstruct the exact code being tested (or indicate the presence of local changes that should be shared with the developers). version is suitable for display in an "about" box or a CLI --version output: it can be easily compared against release notes and lists of bugs fixed in various releases.

The installer adds the following text to your __init__.py to place a basic version in YOURPROJECT.__version__:

from ._version import get_versions
__version__ = get_versions()['version']
del get_versions

Styles

The setup.cfg style= configuration controls how the VCS information is rendered into a version string.

The default style, "pep440", produces a PEP440-compliant string, equal to the un-prefixed tag name for actual releases, and containing an additional "local version" section with more detail for in-between builds. For Git, this is TAG[+DISTANCE.gHEX[.dirty]] , using information from git describe --tags --dirty --always. For example "0.11+2.g1076c97.dirty" indicates that the tree is like the "1076c97" commit but has uncommitted changes (".dirty"), and that this commit is two revisions ("+2") beyond the "0.11" tag. For released software (exactly equal to a known tag), the identifier will only contain the stripped tag, e.g. "0.11".

Other styles are available. See details.md in the Versioneer source tree for descriptions.

Debugging

Versioneer tries to avoid fatal errors: if something goes wrong, it will tend to return a version of "0+unknown". To investigate the problem, run setup.py version, which will run the version-lookup code in a verbose mode, and will display the full contents of get_versions() (including the error string, which may help identify what went wrong).

Known Limitations

Some situations are known to cause problems for Versioneer. This details the most significant ones. More can be found on Github issues page.

Subprojects

Versioneer has limited support for source trees in which setup.py is not in the root directory (e.g. setup.py and .git/ are not siblings). The are two common reasons why setup.py might not be in the root:

• Source trees which contain multiple subprojects, such as Buildbot, which contains both "master" and "slave" subprojects, each with their own setup.py, setup.cfg, and tox.ini. Projects like these produce multiple PyPI distributions (and upload multiple independently-installable tarballs).
• Source trees whose main purpose is to contain a C library, but which also provide bindings to Python (and perhaps other languages) in subdirectories.

Versioneer will look for .git in parent directories, and most operations should get the right version string. However pip and setuptools have bugs and implementation details which frequently cause pip install . from a subproject directory to fail to find a correct version string (so it usually defaults to 0+unknown).

pip install --editable . should work correctly. setup.py install might work too.

Pip-8.1.1 is known to have this problem, but hopefully it will get fixed in some later version.

Bug #38 is tracking this issue. The discussion in PR #61 describes the issue from the Versioneer side in more detail. pip PR#3176 and pip PR#3615 contain work to improve pip to let Versioneer work correctly.

Versioneer-0.16 and earlier only looked for a .git directory next to the setup.cfg, so subprojects were completely unsupported with those releases.

Editable installs with setuptools <= 18.5

setup.py develop and pip install --editable . allow you to install a project into a virtualenv once, then continue editing the source code (and test) without re-installing after every change.

"Entry-point scripts" (setup(entry_points={"console_scripts": ..})) are a convenient way to specify executable scripts that should be installed along with the python package.

These both work as expected when using modern setuptools. When using setuptools-18.5 or earlier, however, certain operations will cause pkg_resources.DistributionNotFound errors when running the entrypoint script, which must be resolved by re-installing the package. This happens when the install happens with one version, then the egg_info data is regenerated while a different version is checked out. Many setup.py commands cause egg_info to be rebuilt (including sdist, wheel, and installing into a different virtualenv), so this can be surprising.

Bug #83 describes this one, but upgrading to a newer version of setuptools should probably resolve it.

Updating Versioneer

To upgrade your project to a new release of Versioneer, do the following:

• install the new Versioneer (pip install -U versioneer or equivalent)
• edit setup.cfg, if necessary, to include any new configuration settings indicated by the release notes. See UPGRADING for details.
• re-run versioneer install in your source tree, to replace SRC/_version.py
• commit any changed files

Future Directions

This tool is designed to make it easily extended to other version-control systems: all VCS-specific components are in separate directories like src/git/ . The top-level versioneer.py script is assembled from these components by running make-versioneer.py . In the future, make-versioneer.py will take a VCS name as an argument, and will construct a version of versioneer.py that is specific to the given VCS. It might also take the configuration arguments that are currently provided manually during installation by editing setup.py . Alternatively, it might go the other direction and include code from all supported VCS systems, reducing the number of intermediate scripts.

License

To make Versioneer easier to embed, all its code is dedicated to the public domain. The _version.py that it creates is also in the public domain. Specifically, both are released under the Creative Commons "Public Domain Dedication" license (CC0-1.0), as described in https://creativecommons.org/publicdomain/zero/1.0/ .