python: determine if a class is nested

Question

Suppose you have a python method that gets a type as parameter; is it possible to determine if the given type is a nested class?
E.g. in this example:

def show_type_info(t):
    print t.__name__
    # print outer class name (if any) ...

class SomeClass:
    pass

class OuterClass:
    class InnerClass:
        pass

show_type_info(SomeClass)
show_type_info(OuterClass.InnerClass)

I would like the call to show_type_info(OuterClass.InnerClass) to show also that InnerClass is defined inside OuterClass.

Answer 1

AFAIK, given a class and no other information, you can't tell whether or not it's a nested class. However, see here for how you might use a decorator to determine this.

The problem is that a nested class is simply a normal class that's an attribute of its outer class. Other solutions that you might expect to work probably won't -- inspect.getmro, for example, only gives you base classes, not outer classes.

Also, nested classes are rarely needed. I would strongly reconsider whether that's a good approach in each particular case where you feel tempted to use one.