动态生成字典键[duplicate]

class D(dict):
    def __missing__(self, key):
        self[key] = D()
        return self[key]

d = D()
d['a']['b']['c'] = 3

您可以使用元组作为dict的键,这样就不必担心子字典了:

mydict[(key,subkey,subkey2)] = "value"

collections.defaultdict .

对于两个级别,这很简单:

>>> from collections import defaultdict
>>> d = defaultdict(dict)
>>> d['key']['subkey'] = 'value'
>>> d['key']['subkey']
'value'

>>> d = defaultdict(lambda: defaultdict(dict))
>>> d['key']['subkey']['subkey2'] = 'value'
>>> d['key']['subkey']['subkey2']
'value'

from collections import defaultdict
d = defaultdict(lambda : defaultdict(int))
>>> d['a']['b'] += 1
>>> d
defaultdict(<function <lambda> at 0x652f0>, {'a': defaultdict(<type 'int'>, {'b': 1})})
>>> d['a']['b']
1

http://tumble.philadams.net/post/85269428/python-nested-defaultdicts

必须使用lambdas来实现内部默认集合肯定不太好,但显然是必要的。