L3·Functions & Modules
λLambdas & Higher-Order Functions
Anonymous functions and map/filter/sorted.
lambdamapfiltersortedkey
§ 1lambda
lambda params: expression — one expression only. Not for statements.
§ 2map / filter
Lazy iterators. Often clearer as comprehensions.
§ 3sorted(key=...)
key is a function called once per item — the classic lambda use case.
Example
1people = [("Ada", 36), ("Bob", 42), ("Cai", 29)]2by_age = sorted(people, key=lambda p: p[1])3print(by_age)Try it live · Python runs in your browser
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Checkpoint quiz
Question 1 / 2
How many statements can a lambda body contain?