Frédéric Gobry wrote:
I've started using setuptools as a developer quite recently, and appreciate the extra features. I've a question though, regarding the way dependencies are resolved when installing such a package: I've written a package that uses elementtree, and would have found natural to add it in install_requires. However, I've already installed it as a debian package, and in the current state setuptools tries to reinstall over it.
Note that it doesn't install *over* it at all. A normal "python setup.py install" without setuptools and with Debian's default distutils.cfg *will* install over it, but with setuptools/easy_install it will not. If you install multiversion (-m to easy_install) then you won't really have effected the system at all except for packages that specifically require ElementTree through setuptools mechanisms. Altogether it is much lower impact than normal distutils installs.
So, should I add some extra logic to the setup.py script (ie, try the dependencies myself) or is there a way to tell it "don't update the dependence if you can already import the module" in a convenient way?
There is a new option, added largely for Debian and other packagers, of python setup.py install --single-version-externally-managed. However, this doesn't add the information to an already-installed package, instead it allows package maintainers to add that egg information without otherwise effecting the layout they are using for libraries. It would almost be reasonable to add this metadata to a package that is already installed, except that I don't know how setuptools could figure out the metadata (version, distribution name) except through Debian-specific hooks. Though it is not unreasonable to write the files by hand -- I think all you need is a directory like ElementTree-VERSION.egg-info/, with one or two files in it. -- Ian Bicking / ianb@colorstudy.com / http://blog.ianbicking.org