defaultdict of defaultdict of int

Question

How do I do defaultdict(defaultdict(int))?

I tried the nested defaultdict method:

def ddict():
    return defaultdict(ddict)

I am looking to do the following:

m['a']['b'] += 1

Answer 1

Try this:

from collections import defaultdict

m = defaultdict(lambda: defaultdict(int))
m['a']['b'] += 1

Note if you want more depth, you can still use a recursive approach:

def ddict(some_type, depth=0):
    if depth == 0:
        return defaultdict(some_type)
    else:
        return defaultdict(lambda: ddict(some_type, depth-1))

m = ddict(int, depth=2)
m['a']['b']['c'] += 1