example

Nesting and using defaultdict in layers
I can not get angry if I write a nonexistent key like d["x"]["y"]["z"]
Maybe a good girl may not be imitating

 >>> from collections import defaultdict 
 >>> d = defaultdict(lambda: defaultdict(lambda: defaultdict(lambda: 0))) 
 >>> d["a"]["b"]["c"] = 1 
 >>> d["a"]["b"]["c"] 
 1 
 >>> d["x"]["y"]["z"] 
 0

If you write in ruby

It was such a feeling. This is also a good girl.

 [27] pry(main)> h = Hash.new(Hash.new(Hash.new(0))) 
 => {} 
 [28] pry(main)> h["a"]["b"]["c"] = 1 
 => 1 
 [29] pry(main)> h["a"]["b"]["c"] 
 => 1 
 [30] pry(main)> h["x"]["y"]["z"] 
 => 0

ref

How to use Python defaultdict-Qiita

Original by Github issue

チャットメンバー募集

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