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SF bug # 493951 string.{starts,ends}with vs slices 

Handle negative indices similar to slices.
This commit is contained in:
Neal Norwitz 2002-06-14 00:50:42 +00:00
parent 585775bf11
commit 1f68fc7fa5
4 changed files with 70 additions and 45 deletions
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4
Doc/whatsnew/whatsnew23.tex
View File

@ -497,6 +497,10 @@ u'\u4001abc'
>>>
\end{verbatim}
\item The \method{startswith()} and \method{endswith()}
string methods now have accept negative numbers for
start and end parameters.
\item Another new string method is \method{zfill()}, originally a
function in the \module{string} module. \method{zfill()} pads a
numeric string with zeros on the left until it's the specified width.

27
Lib/test/string_tests.py
View File

@ -223,6 +223,18 @@ def run_method_tests(test):
test('startswith', 'helloworld', 1, 'lowo', 3, 7)
test('startswith', 'helloworld', 0, 'lowo', 3, 6)
# test negative indices in startswith
test('startswith', 'hello', 1, 'he', 0, -1)
test('startswith', 'hello', 1, 'he', -53, -1)
test('startswith', 'hello', 0, 'hello', 0, -1)
test('startswith', 'hello', 0, 'hello world', -1, -10)
test('startswith', 'hello', 0, 'ello', -5)
test('startswith', 'hello', 1, 'ello', -4)
test('startswith', 'hello', 0, 'o', -2)
test('startswith', 'hello', 1, 'o', -1)
test('startswith', 'hello', 1, '', -3, -3)
test('startswith', 'hello', 0, 'lo', -9)
test('endswith', 'hello', 1, 'lo')
test('endswith', 'hello', 0, 'he')
test('endswith', 'hello', 1, '')
@ -238,6 +250,21 @@ def run_method_tests(test):
test('endswith', 'ab', 0, 'ab', 0, 1)
test('endswith', 'ab', 0, 'ab', 0, 0)
# test negative indices in endswith
test('endswith', 'hello', 1, 'lo', -2)
test('endswith', 'hello', 0, 'he', -2)
test('endswith', 'hello', 1, '', -3, -3)
test('endswith', 'hello', 0, 'hello world', -10, -2)
test('endswith', 'helloworld', 0, 'worl', -6)
test('endswith', 'helloworld', 1, 'worl', -5, -1)
test('endswith', 'helloworld', 1, 'worl', -5, 9)
test('endswith', 'helloworld', 1, 'world', -7, 12)
test('endswith', 'helloworld', 1, 'lowo', -99, -3)
test('endswith', 'helloworld', 1, 'lowo', -8, -3)
test('endswith', 'helloworld', 1, 'lowo', -7, -3)
test('endswith', 'helloworld', 0, 'lowo', 3, -4)
test('endswith', 'helloworld', 0, 'lowo', -8, -2)
test('zfill', '123', '123', 2)
test('zfill', '123', '123', 3)
test('zfill', '123', '0123', 4)

3
Misc/NEWS
View File

@ -6,6 +6,9 @@ Type/class unification and new-style classes
Core and builtins
- Fixed string.startswith and string.endswith builtin methods
so they accept negative indices. [SF bug 493951]
- Fixed a bug with a continue inside a try block and a yield in the
finally clause. [SF bug 567538]

79
Objects/stringobject.c
View File

@ -1310,6 +1310,21 @@ _PyString_Join(PyObject *sep, PyObject *x)
return string_join((PyStringObject *)sep, x);
}
static void
string_adjust_indices(int *start, int *end, int len)
{
if (*end > len)
*end = len;
else if (*end < 0)
*end += len;
if (*end < 0)
*end = 0;
if (*start < 0)
*start += len;
if (*start < 0)
*start = 0;
}
static long
string_find_internal(PyStringObject *self, PyObject *args, int dir)
{
@ -1332,16 +1347,7 @@ string_find_internal(PyStringObject *self, PyObject *args, int dir)
else if (PyObject_AsCharBuffer(subobj, &sub, &n))
return -2;
if (last > len)
last = len;
if (last < 0)
last += len;
if (last < 0)
last = 0;
if (i < 0)
i += len;
if (i < 0)
i = 0;
string_adjust_indices(&i, &last, len);
if (dir > 0) {
if (n == 0 && i <= last)
@ -1763,16 +1769,8 @@ string_count(PyStringObject *self, PyObject *args)
else if (PyObject_AsCharBuffer(subobj, &sub, &n))
return NULL;
if (last > len)
last = len;
if (last < 0)
last += len;
if (last < 0)
last = 0;
if (i < 0)
i += len;
if (i < 0)
i = 0;
string_adjust_indices(&i, &last, len);
m = last + 1 - n;
if (n == 0)
return PyInt_FromLong((long) (m-i));
@ -2169,7 +2167,7 @@ string_startswith(PyStringObject *self, PyObject *args)
const char* prefix;
int plen;
int start = 0;
int end = -1;
int end = INT_MAX;
PyObject *subobj;
if (!PyArg_ParseTuple(args, "O|O&O&:startswith", &subobj,
@ -2193,23 +2191,15 @@ string_startswith(PyStringObject *self, PyObject *args)
else if (PyObject_AsCharBuffer(subobj, &prefix, &plen))
return NULL;
/* adopt Java semantics for index out of range. it is legal for
* offset to be == plen, but this only returns true if prefix is
* the empty string.
*/
if (start < 0 || start+plen > len)
string_adjust_indices(&start, &end, len);
if (start+plen > len)
return PyBool_FromLong(0);
if (!memcmp(str+start, prefix, plen)) {
/* did the match end after the specified end? */
if (end < 0)
return PyBool_FromLong(1);
else if (end - start < plen)
return PyBool_FromLong(0);
if (end-start >= plen)
return PyBool_FromLong(!memcmp(str+start, prefix, plen));
else
return PyBool_FromLong(1);
}
else return PyBool_FromLong(0);
return PyBool_FromLong(0);
}
@ -2228,8 +2218,7 @@ string_endswith(PyStringObject *self, PyObject *args)
const char* suffix;
int slen;
int start = 0;
int end = -1;
int lower, upper;
int end = INT_MAX;
PyObject *subobj;
if (!PyArg_ParseTuple(args, "O|O&O&:endswith", &subobj,
@ -2253,15 +2242,17 @@ string_endswith(PyStringObject *self, PyObject *args)
else if (PyObject_AsCharBuffer(subobj, &suffix, &slen))
return NULL;
if (start < 0 || start > len || slen > len)
string_adjust_indices(&start, &end, len);
if (end-start < slen || start > len)
return PyBool_FromLong(0);
upper = (end >= 0 && end <= len) ? end : len;
lower = (upper - slen) > start ? (upper - slen) : start;
if (upper-lower >= slen && !memcmp(str+lower, suffix, slen))
return PyBool_FromLong(1);
else return PyBool_FromLong(0);
if (end-slen > start)
start = end - slen;
if (end-start >= slen)
return PyBool_FromLong(!memcmp(str+start, suffix, slen));
else
return PyBool_FromLong(0);
}