Operating-system specific requirements with pip

Question

Is it possible to have OS specific requirements in pip's requirements.txt file?

For example: I have a dependency on readline, therefore, if installing on windows (or OSX), then pyreadline is a requirement. If it's linux, then I don't want to force an install.

Answer 1

You can do this with "Environment Markers" as specified in PEP-508:

Here's an example of using such a marker inside a requirements.txt:

pyreadline==2.1; platform_system == "Windows"

Similarly, in a setup.py:

setup(
    ...
    install_requires=['pyreadline; platform_system == "Windows"'],
)