[Tutor] Iterable Understanding

[Martin Walsh]

Stephen Nelson-Smith wrote:
> Martin,
> 
>>    def __iter__(self):
>>        while True:
>>            for logline in self.logfile:
>>                heappush(self.heap, (timestamp(logline), logline))
>>                if len(self.heap) >= self.jitter:
>>                    break
>>            try:
>>                yield heappop(self.heap)
>>            except IndexError:
>>                raise StopIteration
> 
> In this __iter__ method, why are we wrapping a for loop in a while True?
> 
> S.

Are you more interested in one of the loops over the other? Do you have
a more specific question?

The for loop is a means to populate the heap to a predefined size before
this iterator yields any values. You may have noticed that the first
time through the heap is empty so it will loop a number of times, as
defined by self.jitter, while subsequent entries into the loop will
break after only one execution. Perhaps not the most efficient approach
-- not sure either way, you'll have to test.

The while True loop is where values are yielded, until the heap is empty
again (heappop raises an IndexError) -- a fairly common pattern for
generators in general, I think.

The way I see it (not a programmer by trade or training, FWIW), both
loops have something like a do-until style.

HTH,
Marty