Steve Holden wrote:
> Bryan Olson wrote:
>> [...] I see no good reason for the following
>> to happily print 'y'.
>>
>> s = 'buggy'
>> print s[s.find('w')]
>>
>> > Before using the result you always have to perform
>> > a test to discriminate between the found and not found cases. So I
>> don't
>> > really see why this wart has put such a bug up your ass.
>>
>> The bug that got me was what a slice object reports as the
>> 'stop' bound when the step is negative and the slice includes
>> index 0. Took me hours to figure out why my code was failing.
>>
>> The double-meaning of -1, as both an exclusive stopping bound
>> and an alias for the highest valid index, is just plain whacked.
>> Unfortunately, as negative indexes are currently handled, there
>> is no it-just-works value that slice could return.
>>
>>
> If you want an exception from your code when 'w' isn't in the string you
> should consider using index() rather than find.
That misses the point. The code is a hypothetical example of
what a novice or imperfect Pythoners might have to deal with.
The exception isn't really wanted; it's just vastly superior to
silently returning a nonsensical value.
> Otherwise, whatever find() returns you will have to have an "if" in
> there to handle the not-found case.
>
> This just sounds like whining to me. If you want to catch errors, use a
> function that will raise an exception rather than relying on the
> invalidity of the result.
I suppose if you ignore the real problems and the proposed
solution, it might sound a lot like whining.
--
--Bryan
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