Issue 3301: Bisect functions behaved badly when lo was negative.

Lib/bisect.py

@@ -9,6 +9,8 @@ def insort_right(a, x, lo=0, hi=None):
     slice of a to be searched.
     """
 
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
     if hi is None:
         hi = len(a)
     while lo < hi:
@@ -30,6 +32,8 @@ def bisect_right(a, x, lo=0, hi=None):
     slice of a to be searched.
     """
 
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
     if hi is None:
         hi = len(a)
     while lo < hi:
@@ -49,6 +53,8 @@ def insort_left(a, x, lo=0, hi=None):
     slice of a to be searched.
     """
 
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
     if hi is None:
         hi = len(a)
     while lo < hi:
@@ -69,6 +75,8 @@ def bisect_left(a, x, lo=0, hi=None):
     slice of a to be searched.
     """
 
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
     if hi is None:
         hi = len(a)
     while lo < hi:

Lib/test/test_bisect.py

@@ -114,6 +114,14 @@ class TestBisect(unittest.TestCase):
             self.assertEqual(func(data, elem), expected)
             self.assertEqual(func(UserList(data), elem), expected)
 
+    def test_negative_lo(self):
+        # Issue 3301
+        mod = self.module
+        self.assertRaises(ValueError, mod.bisect_left, [1, 2, 3], 5, -1, 3),
+        self.assertRaises(ValueError, mod.bisect_right, [1, 2, 3], 5, -1, 3),
+        self.assertRaises(ValueError, mod.insort_left, [1, 2, 3], 5, -1, 3),
+        self.assertRaises(ValueError, mod.insort_right, [1, 2, 3], 5, -1, 3),
+
     def test_random(self, n=25):
         from random import randrange
         for i in xrange(n):

Misc/NEWS

@@ -10,6 +10,7 @@ What's New in Python 2.6 beta 2?
 Core and Builtins
 -----------------
 
+
 - Issue #2517: Allow unicode messages in Exceptions again by correctly
   bypassing the instance dictionary when looking up __unicode__ on
   new-style classes.
@@ -40,6 +41,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #3301: Bisect module modules behaved badly when lo was negative.
+
 - Issue #839496: SimpleHTTPServer used to open text files in text mode. This is
   both unnecessary (HTTP allows text content to be sent in several forms) and
   wrong because the actual transmitted size could differ with the

Modules/_bisectmodule.c

@@ -11,6 +11,10 @@ internal_bisect_right(PyObject *list, PyObject *item, Py_ssize_t lo, Py_ssize_t
 	PyObject *litem;
 	Py_ssize_t mid, res;
 
+	if (lo < 0) {
+		PyErr_SetString(PyExc_ValueError, "lo must be non-negative");
+		return -1;
+	}
 	if (hi == -1) {
 		hi = PySequence_Size(list);
 		if (hi < 0)
@@ -108,6 +112,10 @@ internal_bisect_left(PyObject *list, PyObject *item, int lo, int hi)
 	PyObject *litem;
 	int mid, res;
 
+	if (lo < 0) {
+		PyErr_SetString(PyExc_ValueError, "lo must be non-negative");
+		return -1;
+	}
 	if (hi == -1) {
 		hi = PySequence_Size(list);
 		if (hi < 0)