Merged revisions 75714 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r75714 | mark.dickinson | 2009-10-26 14:18:44 +0000 (Mon, 26 Oct 2009) | 1 line
Warn against replacing PyNumber_Add with PyNumber_InPlaceAdd in sum
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diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index ab6049c..297c795 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1958,6 +1958,15 @@
}
break;
}
+ /* It's tempting to use PyNumber_InPlaceAdd instead of
+ PyNumber_Add here, to avoid quadratic running time
+ when doing 'sum(list_of_lists, [])'. However, this
+ would produce a change in behaviour: a snippet like
+
+ empty = []
+ sum([[x] for x in range(10)], empty)
+
+ would change the value of empty. */
temp = PyNumber_Add(result, item);
Py_DECREF(result);
Py_DECREF(item);