[Python-Dev] Bug or not? Different behaviour iterating list andcollections.deque (original) (raw)

Christos Georgiou tzot at mediconsa.com
Sun Jan 7 19:23:44 CET 2007

"Josiah Carlson" <jcarlson at uci.edu> wrote in message news:20070107095022.8D37.JCARLSON at uci.edu...

"Christos Georgiou" <tzot at mediconsa.com> wrote:

[snip] issue, but please understand this is not a question for help to change the algorithm (this has been done already), so it's not a question of c.l.py. It's a matter of discrepancy. [snip] [snip Josiah's wordy "it's intentional and not a bug" in the form of a suggestion for a change of algorithm]

Like I said, this wasn't a c.l.py question, even if you thought it deserved a c.l.py answer. In any case, you answered my question, and thank you. It not being a bug suits me just fine.

Allow me to make sure we talk about the same thing here, though: both the example code I provided and the original one do modify the iterable only between the following A and B points in time:

Point A: itertools.chain calls iter() on the iterable.

(Appending to the iterable (list, deque) occur here, and only here.)

Point B: itertools.chain starts calling iterable.next().

This is a different case from the one mentioned in the post by Raymond, and that is why I asked. For example, if itertools.chain called iter() on its arguments when actually needing to iterate over them instead of at the beginning, the code would work. But I really, really don't mind whatever the function, as long as it's by design, and that's the reason I didn't submit a bug in the tracker. That's all. I won't (and never intended) to defend any algorithms.

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