Python · Theory

filter()

Theory

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filter() is built into Python. You do not import it. Freshers only need one honest call and the printed result — not a long definition.

filter() — output — [30]. Only values > 20.

Wrong type often raises TypeError. Empty values matter for bool/all/any. Don’t mix filter up with a similar name (sorted vs sort, int vs float).

Exam tip

Call filter() once and say what prints.

# filter()
print(list(filter(lambda n: n > 20, [10, 30, 20])))

filter() — output: [30]. Only values > 20.