Iteratoration question
andrew cooke
andrew at acooke.org
Thu Apr 2 19:08:43 EDT 2009
grocery_stocker wrote:
>
>>
>> in summary: iterator is bound to one instance of "it", while some_func()
>> returns a new instance each time it is called.
>>
>> BUT
>>
>> while what you are doing is interesting, it is not the same as Python's
>> iterators, which use "yield" from a function and don't require storing a
>> value in a class. look for "yield" in the python docs. this comment
>> may
>> be irrelevant; i am just worried you are confusing the above (which
>> apart
>> from the mistake about instances is perfectly ok) and python's iterators
>> (which use next(), yield, etc).
>>
>
> Okay, one last question for now
>
> When I have the follow class
>
>>>> class it:
> ... def __init__(self):
> ... self.count = -1
> ... def next(self):
> ... self.count +=1
> ... if self.count < 4:
> ... return self.count
> ... else:
> ... raise StopIteraton
> ...
>
>
>
>>>> value = it()
>
> How comes I can;t go over 'value' like in the following
>
>>>> for x in value:
> ... print x
> ...
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> TypeError: iteration over non-sequence
>
> But yet, I can do...
>
>>>> value.next()
> 0
>>>> value.next()
> 1
>>>> value.next()
> 2
>>>> value.next()
> 3
replace return with yield and it might work.
i have to go eat, but if it doesn't read the python docs on iterators -
for example http://docs.python.org/reference/expressions.html#index-1825
andrew
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