More Pythonic way of counting things in a heavily nested defaultdict

defaultdict, python

Solution

from collections import defaultdict

class _defaultdict(defaultdict):
    def __add__(self, other):
        return other

def CountTree():
    return _defaultdict(CountTree)

>>> t = CountTree()
>>> t['a']
defaultdict(<function CountTree at 0x9e5c3ac>, {})
>>> t['a']['b']['c'] += 1
>>> print t['a']['b']['c']
1

Problem

My code currently has to count things in a heavily nested `dict` into another. I have items that need to be indexed by 3 values and then counted. So, before my loop, I initialize a nested `defaultdict` like so: ``` from collections import defaultdict type_to_count_dic = defaultdict( lambda: defaultdict( lambda: defaultdict(int) ) ) ``` Which allows me to count the items within a tight loop like so: ``` for a in ...: for b in ...: for c in ...: type_to_count_dic[a][b][c] += 1 ``` I feel like initializing all those `defaultdict`s feels a lot like making a type declaration in something like Java. Is there a more idiomatic/Pythonic way of doing something like this?

Original source