[Python-checkins] r58895 - in python/trunk: Lib/test/test_dict.py Objects/dictobject.c

[raymond.hettinger]

Author: raymond.hettinger
Date: Wed Nov  7 03:26:17 2007
New Revision: 58895

Modified:
   python/trunk/Lib/test/test_dict.py
   python/trunk/Objects/dictobject.c
Log:
Optimize dict.fromkeys() with dict inputs.  Useful for resetting bag/muliset counts for example.

Modified: python/trunk/Lib/test/test_dict.py
==============================================================================
--- python/trunk/Lib/test/test_dict.py	(original)
+++ python/trunk/Lib/test/test_dict.py	Wed Nov  7 03:26:17 2007
@@ -243,6 +243,10 @@
 
         self.assertRaises(Exc, baddict2.fromkeys, [1])
 
+        # test fast path for dictionary inputs
+        d = dict(zip(range(6), range(6)))
+        self.assertEqual(dict.fromkeys(d, 0), dict(zip(range(6), [0]*6)))
+
     def test_copy(self):
         d = {1:1, 2:2, 3:3}
         self.assertEqual(d.copy(), {1:1, 2:2, 3:3})

Modified: python/trunk/Objects/dictobject.c
==============================================================================
--- python/trunk/Objects/dictobject.c	(original)
+++ python/trunk/Objects/dictobject.c	Wed Nov  7 03:26:17 2007
@@ -1184,6 +1184,25 @@
 	if (d == NULL)
 		return NULL;
 
+	if (PyDict_CheckExact(d) && PyDict_CheckExact(seq)) {
+		PyDictObject *mp = (PyDictObject *)d;
+		PyObject *oldvalue;
+		Py_ssize_t pos = 0;
+		PyObject *key;
+		long hash;
+
+		if (dictresize(mp, ((PyDictObject *)seq)->ma_used))
+			return NULL;
+
+		while (_PyDict_Next(seq, &pos, &key, &oldvalue, &hash)) {
+			Py_INCREF(key);
+			Py_INCREF(value);
+			if (insertdict(mp, key, hash, value))
+				return NULL;
+		}
+		return d;
+	}
+
 	if (PyDict_CheckExact(d) && PyAnySet_CheckExact(seq)) {
 		PyDictObject *mp = (PyDictObject *)d;
 		Py_ssize_t pos = 0;