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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).