Python 2.5 quick reference

This function is useful for removing some of the elements of a sequence. You must provide a filtering function that takes one argument and returns a Boolean value. Here is the calling sequence:

filter(f, S)

The filtering function f is the first argument. It is applied to every element of some sequence S. The result is a new sequence of the same type as S, containing only those elements x of S for which f(x) returned True.

>>> def isOdd(x):
...     if (x%2) == 1: return True
...     else: return False
... 
>>> filter(isOdd, [88, 43, 65, -11, 202])
[43, 65, -11]
>>> filter(isOdd, (1, 2, 4, 6, 9, 3, 3))
(1, 9, 3, 3)
>>> def isLetter(c):
...     return c.isalpha()
... 
>>> filter(isLetter, "01234abcdeFGHIJ*(&!^")
'abcdeFGHIJ'