import sets
class Keeper(object):
def __init__(self, keep):
self.keep = sets.Set(map(ord, keep))
def __getitem__(self, n):
if n not in self.keep:
return None
return unichr(n)
def __call__(self, s):
return s.translate(self)
makefilter = Keeper
if __name__ == '__main__':
just_vowels = makefilter('aeiouy')
print just_vowels(u'four score and seven years ago')
print just_vowels(u'tiger, tiger burning bright')