[Python-3000] Should len() clip to sys.maxsize or raiseOverflowError?

[Dj Gilcrease]

why would it raise an index error when log_entries has more indicies
then sys.maxsize, it should just check the entry @ sys.maxsize.

Maybe I missed it, but why cant len just return an int, which if I
remember correctly is now a long in py3k, so on a 64 bit system len
would (hopefully) never lie, but on a 32 bit system it could return a
number segnificently lower then the actual number of entries.

On 9/2/08, Guido van Rossum <guido at python.org> wrote:
> On Tue, Sep 2, 2008 at 12:08 PM, Raymond Hettinger <python at rcn.com> wrote:
>> From: "Guido van Rossum" <guido at python.org>
>>>
>>> The way I see it is that there are tons of ways I can think of how
>>> raising OverflowError can break unsuspecting programs (e.g. code that
>>> has been tested before but never with a humungous input), whereas
>>> returning a "little white lie" would allow such code to proceed just
>>> fine. Some examples of code that is inconvenienced by the exception:
>>>
>>> if len(x): # used as non-empty test
>>> if len(x) > 100: # used to guarantee we can access items 0 through 99
>>> for i in range(len(x)): # will be broken out before reaching the end
>>
>> That makes sense to me and there a probably plenty of examples.
>> However, I worry more about other examples that will fail
>> and do so it a way that is nearly impossible to find through
>> code review (because the code IS correct as written).
>>
>>  n = len(log_entries)
>>  if log_entries[n] in handled:
>
> This should raise an IndexError. I think you meant something else?
>
>>     log_entries.pop(n)
>>
>> It's not hard to imagine other examples with slicing and whatnot.
>> These cases may be less common that those pointed out by Guido
>> but they will be disasterous when they occur and very hard to
>> defend against or debug.
>>
>> I would rather face the overflow errors when they arise than
>> deal with the latter cases.   In the former, I can always make an
>> immediate
>> fix by replacing the builtin with an Overflow suppressing version.
>> But, in the latter case, the silent failure is *much* harder to deal with.
>>
>>
>> Raymond
>>
>
>
>
> --
> --Guido van Rossum (home page: http://www.python.org/~guido/)
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