Built-in Functions

filter()

Keep items that pass a test.

filter(function, iterable)

filter() constructs an iterator from elements of iterable for which function returns True.

If function is None, all falsy elements are removed.

Parameters

Name	Description
function	A function that returns true or false for each item, or `None` to keep truthy items.
iterable	The items to test.

A filter iterator containing the kept items.

Run it and change it

numbers = [1, 2, 3, 4]
evens = filter(lambda n: n % 2 == 0, numbers)
print(list(evens))

Filtering falsy values: list(filter(None, [0, 1, False, 2, '', 'hello'])) cleanly extracts [1, 2, 'hello'].