map

Description

Applies function to every item of an iterable and returns a list of the results.

Syntax

map (function, iterable [, …])

function

Required. A function that is used to create a new list.

iterable

Required. An iterable object or multiple comma-seperated iterable objects.

Return Value

list

Time Complexity

#TODO

Remarks

If additional iterable arguments are passed, function must take that many arguments and is applied to the items from all iterables in parallel. If one iterable is shorter than another it is assumed to be extended with None items. If function is None, the identity function is assumed; if there are multiple arguments, map() returns a list consisting of tuples containing the corresponding items from all iterables (a kind of transpose operation). The iterable arguments may be a sequence or any iterable object; the result is always a list.

Example 1

>>> map(lambda x: x+x, (1, 2, 3))
[2, 4, 6]
>>> map(lambda x, y: x/y, (1, 4, 9), (1, 2, 3))
[1, 2, 3]
>>> map(lambda x, y, z: x+y+z, (1, 2, 3), (1, 4, 9), (1, 16, 27))
[3, 22, 39]

Example 2

>>> map(None, [True, False])
[True, False]
>>> map(None, ['a', 'b'], [1, 2])
[('a', 1), ('b', 2)]
>>> map(None, ['a', 'b'], [1, 2, 3])
[('a', 1), ('b', 2), (None, 3)]

See Also

reduce(), filter() and Comprehensions and Generator Expression.