malkarouri schreef:
> Hi everyone,
>
> I have an algorithm in which I need to use a loop over a queue on
> which I push values within the loop, sort of:
>
> while not(q.empty()):
> x = q.get()
> #process x to get zero or more y's
> #for each y:
> q.put(y)
>
> The easiest thing I can do is use a list as a queue and a normal for
> loop:
>
> q = [a, b, c]
>
> for x in q:
> #process x to get zero or more y's
> q.append(y)
>
> It makes me feel kind of uncomfortable, though it seems to work. The
> question is: is it guaranteed to work, or does Python expect that you
> wouldn't change the list in the loop?
Changing a loop while iterating over it is to be avoided, if possible.
In any case, a deque is more efficient for this kind of use. I'd use it
like this:
from collections import deque
q = deque([a, b, c])
while q:
x = q.popleft()
# ...
q.append(y)
--
The saddest aspect of life right now is that science gathers knowledge
faster than society gathers wisdom.
-- Isaac Asimov
Roel Schroeven
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