default_dict_example_2.py

from collections import defaultdict

d = defaultdict(int)
print(d["Alice"]) # prints 0

d["Bob"] += 1
print(d["Bob"]) # prints 1 

d = defaultdict(list)
d["John"].append("eggs")
print(d["John"]) # prints ["eggs"]

d = defaultdict(lambda: 100)
d["Alice"] += 1
print(d["Alice"]) # prints 101