It might be useful to introduce a new map() and filter() methods to iterators and iterables. Both methods should accept lambda/function which transforms a single argument into value. Both methods should return another iterator.

# proposed methods usage:
range(10).map(abs).filter(lambda x: x % 5 == 0)
# existing equivalent:
filter(lambda x: x % 5 == 0, map(abs, range(-10, 10)))
# result:
[10, 5, 0, 5]

Rough equivalent of implementation:
class iterator:
    def map(self, fn):
        for v in self:
            yield fn(v)
    
    def filter(self, fn):
        for v in self:
            if fn(v):
                yield v
            else:
                continue

Introduction of such methods will allow to transform collections lazy without significant memory consumption (as was mentioned in http://bugs.python.org/issue912738).