enumerate overflow
Steve Holden
steve at holdenweb.com
Wed Oct 3 10:51:42 EDT 2007
Tim Chase wrote:
>>> for lineNum, line in enumerate(f): ...
>>>
>>> However, lineNum soon overflows and starts counting backwards. How do
>>> i force enumerate to return long integer?
>>>
>> Just how "soon" exactly do you read sys.maxint lines from a file? I
>> should have thought that it would take a significant amount of time to
>> read 2,147,483,647 lines ...
>
> A modestly (but not overwhelmingly) long time:
>
> (defining our own xrange-ish generator that can handle things larger
> than longs)
>
> >>> def xxrange(x):
> ... i = 0
> ... while i < x:
> ... yield i
> ... i += 1
> ...
> >>> for i,j in enumerate(xxrange(2**33)): assert i==j
> ...
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> AssertionError
>
>
> It took me about an 60-90 minutes to hit the assertion on a dual-core
> 2.8ghz machine under otherwise-light-load. If batch-processing lengthy
> log files or other large data such as genetic data, it's entirely
> possible to hit this limit as the OP discovered.
>
I wouldn't dream of suggesting it's impossible. I just regard "soon" as
less than an hour in commuter's terms, I suppose.
regards
Steve
--
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