Returns a sequence from those elements of iterable for which function returns True.

filter (function, iterable)

function

Required. A function. If set to None returns only elements that are True.

iterable

Required. Any iterable sequence.

same as returned by function

#TODO

Note that filter(function, iterable) is equivalent to [item for item in iterable if function(item)] if function is not None and [item for item in iterable if item] if function is None.

See itertools.ifilter() and itertools.ifilterfalse() for iterator versions of this function, including a variation that filters for elements where the function returns False.

>>> def f(x):
...     if x > 0:
...         return x
>>> filter(f, [-1, 0, 1])
[1]

>>> filter(None, (0, 1, True))
(1, True)

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