[Python-Dev] string.find() again (was Re: timsort for jython)

[Tim Peters]

>> and I expect *everyone* here has been saved more than once by that
>>
>>     '' in 'xyz'
>> currently raises an exception.

[Guido]
> I dunno.  The exception has annoyed me too.

Annoyed because it pointed out an error in your code, or because True would
have been a useful result?  It's annoyed me too, but it was always for the
former reason.

> I expect that Andrew Koenig would delight in this question. :-)

Believe me, he already did <wink>.

> I personally see no way to defend ('' in 'x') returning false;

The suggestion is not that it return False, but that it raise an exception,
as in "errors should never pass silently".

> it's so clearly a substring that any definition of substring-ness that
> excludes this seems mathematically wrong, despite your good intentions.

I'd like to see a plausible use case for

    '' in str

returning True, then.  Do keep in mind that nobody can be more anal about
mathematical consistency than me <0.9 wink>, but the real world isn't much
impressed with our abstractions.