[earthboundkid]

Python has too many ways to do it:

    >>> state2name2visited = {}
    >>> state2name2visited.setdefault("PA", {}).setdefault("Joe", []).append("Pittsburgh")
    >>> state2name2visited
    {'PA': {'Joe': ['Pittsburgh']}}

[abcxjeb284]

It’s really 2 ways to do it, and the defaultdict way (I believe) would have less allocations in a deeply nested loop (since this version has to create a {} and a [] every time).

Also setdefault causes confusion for less experienced users in a way that the defaultdict format does not.