How can I specify optional dependencies in a pip requirements file?
According to the pip documentation this is possible, but the documentation doesn't explain how to do it, and I can't find any examples on the web.
Instead of specifying optional dependencies in the same file as the hard requirements, you can create a optional-requirements.txt and a requirements.txt.
To export your current environment's packages into a text file, you can do this:
pip freeze > requirements.txt
If necessary, modify the contents of the requirements.txt to accurately represent your project's dependencies. Then, to install all the packages in this file, run:
pip install -U -r requirements.txt
-U tells pip to upgrade packages to the latest version, and -r tells it to install all packages in requirements.txt.