enumerated while loop

[Roald de Vries]

Dear all,

I sometimes want to use an infinite while loop with access to the loop  
index, like this:

def naturals():
     i = 0
     while True:
     yield i
     y += 1

for i in naturals():
     print(i)

I assume a function like 'naturals' already exists, or a similar  
construction for the same purpose. But what is it called?

Kind regards, Roald