The setdefault Method in Python: Key Value

Returns the value of a key. If the key does not exist, it creates the key with a default value (default is None).

setdefault(key[, default])¶

• key - key whose value must be returned.
• default - default value if key is not in the dictionary.

a = {'one': 1, 'two': 2, 'three': 3}
print(a.setdefault('one'))  # 1
print(a.setdefault('four'))  # None
print(a.setdefault('fifth', 5))  # 5

print(a)  # {'one': 1, 'two': 2, 'three': 3, 'four': None, 'fifth': 5}