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?
--
http://mail.python.org/mailman/listinfo/python-list
