On Wed, 21 Nov 2012 04:43:57 -0800, Giacomo Alzetta wrote:
> I just came across this:
>
>>>> 'spam'.find('', 5)
> -1
>
>
> Now, reading find's documentation:
>
>>>> print(str.find.__doc__)
> S.find(sub [,start [,end]]) -> int
>
> Return the lowest index in S where substring sub is found,
> such that sub is contained within S[start:end]. Optional arguments
> start and end are interpreted as in slice notation.
>
> Return -1 on failure.
>
> Now, the empty string is a substring of every string so how can find
> fail?
> find, from the doc, should be generally be equivalent to
> S[start:end].find(substring) + start, except if the substring is not
> found but since the empty string is a substring of the empty string it
> should never fail.
>
> Looking at the source code for find(in stringlib/find.h):
>
> Py_LOCAL_INLINE(Py_ssize_t)
> stringlib_find(const STRINGLIB_CHAR* str, Py_ssize_t str_len,
> const STRINGLIB_CHAR* sub, Py_ssize_t sub_len,
> Py_ssize_t offset)
> {
> Py_ssize_t pos;
>
> if (str_len < 0)
> return -1;
>
> I believe it should be:
>
> if (str_len < 0)
> return (sub_len == 0 ? 0 : -1);
>
> Is there any reason of having this unexpected behaviour or was this
> simply overlooked?
why would you be searching for an empty string?
what result would you expect to get from such a search?
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