Question

Say I have a package “colorExtentions” and in my __init__.py I have __all__=["red", "blue"]. This package should be able to be extended automatically by adding modules to the directory and to the __all__ list. Is the following acceptable or is there another “best practice” for such kind of things?

import colorExtentions
from colorExtentions import *

for moduleName in colorExtentions.__all__:
    colors.append(moduleName)
promptUserToChoose(colors)

Answer 1

Presuming that each colour is a class, I would argue the nicer solution would be to ensure all of your colours subclass from a single class (which is good design anyway):

class Color:
    ...

Then, when you want a list of all colours, you can simply import any modules that will contain the classes, and do:

from colorExtentions import *

colors = Color.__subclasses__()

This way you end up with a list of each Color subclass.

Note in 2.x, you will need new-style classes (inheriting from object) to have the __subclasses__() method available.