Can a Python package depend on a specific version control revision of another Python package?

Question

Some useful Python packages are broken on pypi, and the only acceptable version is a particular revision in a revision control system. Can that be expressed in setup.py e.g

requires = 'svn://example.org/useful.package/trunk@1234' ?

Answer 1

You need to do two things. First, require the exact version you want, e.g.:

install_requires = "useful.package==1.9dev-r1234"

and then include a dependency_links setting specifying where to find it:

dependency_links = ["svn://example.org/useful.package/trunk@1234#egg=useful.package-1.9dev-r1234"]

Note that the version #egg= part of the dependency_links URL must exactly match what you specified in install_requires; this is what links the two pieces together.

What happens is that setuptools sees the #egg tag on the link and saves the URL as an available download URL for that precise version of the package. Then, when it tries to resolve that requirement later, it should download that precise SVN URL.

(Note, however, that for this to really work, the targeted SVN revision has to actually build an egg with that name and version. Otherwise, your dependency will fail at runtime! So, this really only works if the package you're depending on uses SVN revision tags in their default build version numbers.)

Answer 2

If you really require an obscure version of another package, and there's no way to make do with other versions, you might want to simply distribute that version of the package with your own. If necessary put it in your own namespace to ensure that your version is the one that is used.