Earlier quoted context omitted.
We have to use a mix of pypi and conda since quite a few of our dependencies are not in conda. We have a script which checks conda first, then falls back to pypi, all from one requirements.txt
Any chance you can share that script? I'm looking for something similar, since I too am using both conda and pypi for dependencies.
Instead of requirements.txt we use py.prereqs, but otherwise this script should get you close.