In nested classes, how to access outer class's elements from nested class in Python?

Question

I have this scenario, where I need to ask a nested class to append items to a list in the outer class. Heres pseudocode thats similar to what Im trying to do. How would I go about getting it to work?

class Outer(object):
  outerlist = []
  class Inner(object):
    def __call__(self, arg1):
      outerlist.append(arg1)

if __name__ == "__main__":
  f = Outer()
  f.Inner("apple")
  f.Inner("orange")

  print f.outerlist()

This is what I hope to see - apple, orange

Details:
OS X, Python 2.7

Answer 1

This will have the desired result.

Notice the use of __new__ (line A). This means that instead of doing any construction stuff properly Inner just appends the list. Also, to access class properties of a containing class just use the outer class's name (line B).

Lastly see line C. the list is not a function. You had some extra brackets in your original code.

class Outer(object):
    outerlist = []
    class Inner(object):
        def __new__(self, arg1):                #A
            Outer.outerlist.append(arg1)        #B

f = Outer()
f.Inner("apple")
f.Inner("orange")
print f.outerlist                               #C

Answer 2

You can only access the outer class with the full global name:

class Outer(object):
    outerlist = []
    class Inner(object):
        def __call__(self, arg1):
            Outer.outerlist.append(arg1)

In python, there generally is no need to nest classes in any case. There are use-cases where it makes sense to define a class in a function (to use scoped variabels), but rarely is there a need for nested classes.