SF bug # 493951 string.{starts,ends}with vs slices
Handle negative indices similar to slices.
diff --git a/Doc/whatsnew/whatsnew23.tex b/Doc/whatsnew/whatsnew23.tex
index 0759c9d..6d3651a 100644
--- a/Doc/whatsnew/whatsnew23.tex
+++ b/Doc/whatsnew/whatsnew23.tex
@@ -497,6 +497,10 @@
>>>
\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.
diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index 075e1c9..b645354 100644
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -223,6 +223,18 @@
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 @@
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)
diff --git a/Misc/NEWS b/Misc/NEWS
index 383614f..4a949f4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -6,6 +6,9 @@
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]
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 243fcc6..5d6478b 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -1310,6 +1310,21 @@
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 @@
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 @@
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 @@
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 @@
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);
- else
- return PyBool_FromLong(1);
- }
- else return PyBool_FromLong(0);
+ if (end-start >= plen)
+ return PyBool_FromLong(!memcmp(str+start, prefix, plen));
+ else
+ return PyBool_FromLong(0);
}
@@ -2228,8 +2218,7 @@
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 @@
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);
}