Question

Python’s lack of static typing makes it possible to use and rely on classes without importing them. Should you import them anyway? Does it matter?

Example

someclass.py

class SomeClass:
    def __init__(self, some_value):
        self.some_value = some_value

someclient.py

class SomeClient:
    def __init__(self, some_class_instance):
        self.some_class_helper = some_class_instance

Here, the functionality of SomeClient clearly relies on SomeClass or at least something that behaves like it. However, someclient.py will work just fine without import someclass. Is this ok? It feels wrong to use something without saying anywhere that you’re even using it.

Answer 1

Yes, it’s completely ok. some_class_instance might be anything, it doesn’t have to be an instance of SomeClass. You might want to pass an instance that looks just like SomeClass, but uses a different implementation for testing purposes, for example.