如何比使用循环更快地生成嵌套字典？

from collections import defaultdict

def nested_dict():
    return defaultdict(nested_dict)

nested = nested_dict()
nested['a']['b']['c'] = 1

keys = ['a', 'b', 'c']
values = [1, 2, 3]
nested = {k1: {k2: {k3: v3} for k3, v3 in zip(keys[2:], values[2:])} for k1, v1 in zip(keys[0], [values[0]]) for k2, v2 in zip(keys[1:], values[1:])}

from functools import reduce

def nested_dict_join(dicts, key):
    return reduce(lambda acc, d: {**acc, key: d}, dicts, {})

nested = nested_dict_join([{'a': 1}, {'b': {'c': 2}}], '')

from boltons.dictutils import DefaultOrderedDict

nested = DefaultOrderedDict(DefaultOrderedDict)
nested['a']['b']['c'] = 1