Issue #3004: Minor fix to slice.indices(). slice(-10).indices(9) now
returns (0, 0, 1) instead of (0, -1, 1), and slice(None, 10, -1).indices(10)
returns (9, 9, -1) instead of (9, 10, -1).
diff --git a/Lib/test/test_slice.py b/Lib/test/test_slice.py
index 83f051f..8c90c10 100644
--- a/Lib/test/test_slice.py
+++ b/Lib/test/test_slice.py
@@ -79,6 +79,20 @@
self.assertEqual(slice(None, None, -1).indices(10), (9, -1, -1))
self.assertEqual(slice(None, None, -2).indices(10), (9, -1, -2))
self.assertEqual(slice(3, None, -2).indices(10), (3, -1, -2))
+ # issue 3004 tests
+ self.assertEqual(slice(None, -9).indices(10), (0, 1, 1))
+ self.assertEqual(slice(None, -10).indices(10), (0, 0, 1))
+ self.assertEqual(slice(None, -11).indices(10), (0, 0, 1))
+ self.assertEqual(slice(None, -10, -1).indices(10), (9, 0, -1))
+ self.assertEqual(slice(None, -11, -1).indices(10), (9, -1, -1))
+ self.assertEqual(slice(None, -12, -1).indices(10), (9, -1, -1))
+ self.assertEqual(slice(None, 9).indices(10), (0, 9, 1))
+ self.assertEqual(slice(None, 10).indices(10), (0, 10, 1))
+ self.assertEqual(slice(None, 11).indices(10), (0, 10, 1))
+ self.assertEqual(slice(None, 8, -1).indices(10), (9, 8, -1))
+ self.assertEqual(slice(None, 9, -1).indices(10), (9, 9, -1))
+ self.assertEqual(slice(None, 10, -1).indices(10), (9, 9, -1))
+
self.assertEqual(
slice(-100, 100 ).indices(10),
slice(None).indices(10)
diff --git a/Misc/NEWS b/Misc/NEWS
index 9e02d76..96d45af 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,13 @@
Core and Builtins
-----------------
+- Issue #3004: Minor change to slice.indices(): the start and stop
+ arguments are now treated identically, making the behaviour easier
+ to describe and understand. For example, slice(None, -10,
+ 1).indices(9) now returns (0, 0, 1) instead of (0, -1, 1), and
+ slice(None, 10, -1).indices(10) returns (9, 9, -1) instead of (9,
+ 10, -1).
+
- Make bin() implementation parallel oct() and hex().
diff --git a/Objects/sliceobject.c b/Objects/sliceobject.c
index 075418e..8748fed 100644
--- a/Objects/sliceobject.c
+++ b/Objects/sliceobject.c
@@ -169,8 +169,9 @@
else {
if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
if (*stop < 0) *stop += length;
- if (*stop < 0) *stop = -1;
- if (*stop > length) *stop = length;
+ if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
+ if (*stop >= length)
+ *stop = (*step < 0) ? length - 1 : length;
}
if ((*step < 0 && *stop >= *start)