One thing I learned yesterday was that requirements.txt supports conditionals like SomeProject==5.4; python_version < '2.7' SomeProject; sys.platform =

One thing I learned yesterday was that requirements.txt supports conditionals like SomeProject==5.4; python_version < '2.7' SomeProject; sys.platform == 'win32' In my view, that's already out of hand, and isn't even really parsable without some bespoke library. I'm a big fan of this idea of having a requirements.lock. I can call pip to do the parsing, then I can parse the lock which is just json. The fact that you need to parse the requirements.txt feels like a design issue with pip to me. (Of course, I'm coming from Rubyland.) As for setup.py, setup.py is broken because it conflates build scripting with package metadata and dependencies. Now that tox exists things are better (but the fact that tox is not a general-purpose programming language is IMO unfortunate coming from Rake/Ruby/Bundler/Gemfiles.)