Often packages will need to depend on files which are not .py files: e.g. images, data tables, documentation, etc. Those files need special treatment in order for setuptools to handle them correctly.
The mechanism that provides this is the MANIFEST.in file. This is relatively quite simple: MANIFEST.in is really just a list of relative file paths specifying files or globs to include.:
include README.rst include docs/*.txt include funniest/data.json
Note
Files which are to be used by your installed library (e.g. data files to support a particular computation method) should usually be placed inside of the Python module directory itself. E.g. in our case, a data file might be at funniest/funniest/data.json. That way, code which loads those files can easily specify a relative path from the consuming module's __file__ variable.