Reduce mandatory packages bloat

I installed the package in a new machine and it installed the following seldom-used packages:

pymeeus, convertdate, korean-lunar-calendar

Any work to reduce (and/or standardize) the number of packaged installed would be helpful to combat package bloat. For example, I have no need for Korean holidays yet I find myself having to install a package that, by its name, is required only for those type of holidays.

[mborsetti]

Hello @dr-prodigy!

I agree with @stianjensen: https://setuptools.pypa.io/en/latest/userguide/dependency_management.html#optional-dependencies is a great tool for this use case.

Specifically:

1. We can target the dependencies that cause the most bloat and segregate them as optional dependencies to be installed as e.g. holidays[lunar] or holidays[islamic] or holidays[lunar,islamic] or whatever they turn out to be;
2. A small amount of code would need to be added to handle import failures with an explanatory error (e.g. “Could not import korean-lunar-calendar; please install using pip install -U holidays[korea]” or whatever the case may be).
3. No changes would be required for testing other than for this purpose we would install dependencies from a new requirements_test.txt file containing all dependencies, including optional ones;
4. The documentation would need to be updated, and the name of optional dependencies added to the relevant countries.

I wish I had time to volunteer to work on this at the moment, but sadly I don’t.

[MRigal]

I would also welcome to have less package bloat. One option often considered by other packages ist to add optionals like holidays[lunar] or holidays[full] for convertdate and other advanced converters.

I also guess that many people won’t need the full set of possible conversions