Summary

There's a delicate dependency on who goes first in the import order because we couple module dependencies (imports) and intialization (code execution at import).

See e.g. #29808 (comment)

Proposed fix

I think we can make this simpler by applying the following rules

• no submodule is allowed to run intialization code (e.g. loading the colormaps) as part of their import
• initialization should be lazy if possible
• if lazy initialization is not possible, the initalization code must be placed in a _mpl_init() function in that module. ( (e.g. it's tricky for colormaps because the colormaps are injected as globals into the cm module)
• only the top-level matplotlib module is allowed to call ._mpl_init() of the submodules.

This way, we can decouple initialization from import and have one central place that orchestrates the initialization.

What do you think?