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

One could use Python's collections.defaultdict instead of creating an AutoVivification class and then instantiating dictionary as an object of that type.

import collections
dictionary = collections.defaultdict(lambda: collections.defaultdict(int))

This will create a dictionary of dictionaries with a default value of 0. When you wish to increment an entry, use:

dictionary[keyword][filename] += 1