Python - 'import' or pass modules as parameters?

Question

I was wondering if passing module objects to a class or object which requires it rather than using import might not be a bad idea, as it avoids hard dependencies on those modules.

I was wondering if someone more aware of the Python Zen than I might be able to explain why this is a terrible/not terrible idea?

Answer 1

What you're talking about is called dependency injection and is considered a good practice for making your code testable. I don't think there's anything about Python that would make it unPythonic or a bad practice.

There are other ways you could do it in Python, for example by importing different modules depending on some kind of flag you pass in:

class Foo(object):     def __init__(self, testing=False):         if testing:             import module_test as module         else:             import module         self.module = module 

But passing a reference to the module you wish to use is more flexible, separates concerns better, and is no less Pythonic than passing a reference to a class or instance (or string or integer) you wish to use.

For the ordinary (non-test) use case, you can use a default argument value:

class Foo(object):     def __init__(self, module=None):         if not module:             import module         self.module = module