python - 自动将键添加到 Python dict

Question

如果键不存在，我想自动将它们添加到 Python 字典中。例如，

a = "a"
b = "b"
c = "c"

dict = {}
dict[a][b] = c # doesn't work because dict[a] doesn't exist

如果 key 不存在，我如何自动创建 key ？

Answer 1

使用 collections.defaultdict :

def recursively_default_dict():
    return collections.defaultdict(recursively_default_dict)

my_dict = recursively_default_dict()
my_dict['a']['b'] = 'c'