Python: How to update value of key value pair in nested dictionary?

Question

i am trying to make an inversed document index, therefore i need to know from all unique words in a collection in which doc they occur and how often.

i have used this an

Answer 1

I think you are trying to add 1 to a dictionary entry that doesn't yet exist. Your getitem method is for some reason returning a new instance of the AutoVivification class when a lookup fails. You're therefore trying to add 1 to a new instance of the class.

I think the answer is to update the getitem method so that it sets the counter to 0 if it doesn't yet exist.

class AutoVivification(dict):
    """Implementation of perl's autovivification feature."""
    def __getitem__(self, item):
        try:
            return dict.__getitem__(self, item)
        except KeyError:
            self[item] = 0
            return 0

Hope this helps.