> I want to raise one other issue here: should
>
> '' in 'xyz'
>
> return True or raise an exception? I've been burned, e.g., by
>
> >>> 'xyz'.startswith('')
> True
> >>>
>
> when '' was computed by an expression that didn't "expect to" reduce to
> nothingness, and I expect *everyone* here has been saved more than once by
> that
>
> '' in 'xyz'
>
> currently raises an exception.
I dunno. The exception has annoyed me too.
> If we make __contains__ act like
>
> 'xyz'.find('') >= 0
>
> that (very probable) error will pass silently in the future:
>
> >>> 'xyz'.find('')
> 0
> >>>
>
> IOW, do we follow find() rigidly, or retain "str1 in str2"'s current
> behavior when str1 is empty?
I expect that Andrew Koenig would delight in this question. :-)
I personally see no way to defend ('' in 'x') returning false; it's so
clearly a substring that any definition of substring-ness that
excludes this seems mathematically wrong, despite your good
intentions.
I guess we'll have to cope in the same way as we cope with the
behavior of find() and startswith() in similar cases.
--Guido van Rossum (home page: http://www.python.org/~guido/)
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