Matplotlib pulls numpy: make lib optional

I was surprised to find numpy as part of my dependencies when I don’t do any maths.

NumPy is a fantastic tool, but it’s heavy and clearly unnecessary for my project. It turns out, numpy is a required dependency of matplotlib, which is now part of needs deps since 0.5.0.

I won’t personally be doing any pie-chart-ing, so wouldn’t really benefit from use of matplotlib, nor numpy. Can we make the matplotlib an optional dependency please? This way, people who are in more “constrained” systems don’t need to pull in the whole maths ecosystem.

From setuptools docs on Optional Dependencies, adapted for us:

    extras_require={
        "matplotlib":  ["matplotlib"],
    }

As for gating the feature in python, from SO:

try:
    import matplotlib
except ImportError:
    # dependency missing, issue a warning
    import warnings
    warnings.warn('matplotlib not found, please install 'matplotlib' extra to enable pie-charts')

I realize there’s a documentation overhead to doing this, but think it’s worth it.

[danieleades]

this is causing me a headache right now, as i’m having build issues when installing numpy

[danwos]

Yes, I agree. There are some (huge) dependencies, which are used for some directives only and therefore are often not needed for most use-cases.

Instead of a warning I would like to throw an exception, as the final documentation build will not contain the expected content (e.g. no pie charts). Otherwise I’m afraid that a user may miss the warning, as sphinx-build logs are normally not so small.

This could also be configurable, e.g. needs_missing_import_exceptions = False (True is default).

Any concerns about raising an exception and stopping build in such a case?