all Python 3Dictionaries (dict)function

dict.setdefault

access

Return the value for a key; if absent, insert it with default and return default.

Syntax

d.setdefault(key, default=None)

The classic idiom is grouping: d.setdefault(k, []).append(x), since the method returns the very object stored in (or just placed into) the dictionary. The default is built on every call even when the key already exists — a fresh empty list is created and immediately discarded — so for heavy grouping collections.defaultdict(list) is cleaner and faster.

Examples

d = {'a': 1}
print(d.setdefault('a', 0))   # → 1
print(d.setdefault('b', 2))   # → 2
print(d)                      # → {'a': 1, 'b': 2}

See also

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