python 值自增字典、动态编号

from collections import defauldict
a = defaultdict(lambda: len(a))

# a dict with auto increasing value
def inc(i=-1):
    def f():
        nonlocal i
        i+=1
        return i
    return f
from collections import defauldict
incdict = lambda i:defaultdict(inc(i-1))
# d = incdict(0)