Reference Requirements.Txt for the Install_Requires Kwarg in Setuptools Setup.Py File

Reference requirements.txt for the install_requires kwarg in setuptools setup.py file

You can flip it around and list the dependencies in setup.py and have a single character — a dot . — in requirements.txt instead.

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Alternatively, even if not advised, it is still possible to parse the requirements.txt file (if it doesn't refer any external requirements by URL) with the following hack (tested with pip 9.0.1):

install_reqs = parse_requirements('requirements.txt', session='hack')

This doesn't filter environment markers though.

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In old versions of pip, more specifically older than 6.0, there is a public API that can be used to achieve this. A requirement file can contain comments (#) and can include some other files (--requirement or -r). Thus, if you really want to parse a requirements.txt you can use the pip parser:

from pip.req import parse_requirements

# parse_requirements() returns generator of pip.req.InstallRequirement objects
install_reqs = parse_requirements(<requirements_path>)

# reqs is a list of requirement
# e.g. ['django==1.5.1', 'mezzanine==1.4.6']
reqs = [str(ir.req) for ir in install_reqs]

setup(
    ...
    install_requires=reqs
)

setup.py doesn't see my requirements.txt

Add requirements.txt to MANIFEST.in.

When to use pip requirements file versus install_requires in setup.py?

My philosophy is that install_requires should indicate a minimum of what you need. It might include version requirements if you know that some versions will not work; but it shouldn't have version requirements where you aren't sure (e.g., you aren't sure if a future release of a dependency will break your library or not).

Requirements files on the other hand should indicate what you know does work, and may include optional dependencies that you recommend. For example you might use SQLAlchemy but suggest MySQL, and so put MySQLdb in the requirements file).

So, in summary: install_requires is to keep people away from things that you know don't work, while requirements files to lead people towards things you know do work. One reason for this is that install_requires requirements are always checked, and cannot be disabled without actually changing the package metadata. So you can't easily try a new combination. Requirements files are only checked at install time.

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