Defaultdict with default custom class

defaultdict_callable.py

from collection import defaultdict

class Number(object):
    def __init__(self, N):
        self.N = N
    
    def __repr__(self):
        return str(self.N)

d = defaultdict(Number)
d['foo']
# TypeError: __init__() takes exactly 2 arguments (1 given)

d = defaultdict(lambda: Number(10))
d['foo']
10

# OR
from functools.partial
d = defaultdict(partial(Number, 10))
d['foo']
10