Python filter / max combo - checking for empty iterator

Question

(Using Python 3.1)

I know this question has been asked many times for the general question of testing if iterator is empty; obviously, there\'s no neat solution to t

Answer 1

If you just want to check if the return of filter is empty, you might do (Python3)

len(list(filter(lambda e : e == 2, [1,2,3])))

But notice, hence filter is a generator if you this test twice, second time, you will receive a diferent result:

len(list(filter(lambda e : e == 2, [1,2,3]))) len(list(filter(lambda e : e == 2, [1,2,3])))

>>> 1

>>> 1

But:

f = filter(lambda e : e == 2, [1,2,3]) len(list(f)) len(list(f))

>>> 1

>>> 0