What happens when you 'break' a generator?
Terry Reedy
tjreedy at udel.edu
Tue Jul 29 03:51:05 EDT 2014
On 7/29/2014 3:18 AM, Frank Millman wrote:
> Hi all
>
> Python 3.4.1
>
> Here is a simple generator -
>
> def test():
> print('start')
> for i in range(5):
> yield i
> print('done')
>
> x = test()
> for j in x:
> print(j)
>
> As expected, the output is -
>
> start
> 0
> 1
> 2
> 3
> 4
> done
>
> Here I break the loop -
>
> x = test()
> for j in x:
> print(j)
> if j == 2:
> break
>
> Now the output is -
>
> start
> 0
> 1
> 2
>
> 'done' does not appear, so the generator does not actually terminate. What
> happens to it?
It sits there waiting for you to ask for the next value. Add
for j in x: print(j)
to exhaust it. Even then, it sits there until garbage collected.
--
Terry Jan Reedy
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