SF patch #421922: Implement rich comparison for dicts.

tim-one · tim-one · commit e63415ead8ae · 2001-05-08T04:38:29.000Z
d1 == d2 and d1 != d2 now work even if the keys and values in d1 and d2
don't support comparisons other than ==, and testing dicts for equality
is faster now (especially when inequality obtains).
diff --git a/Lib/test/test_richcmp.py b/Lib/test/test_richcmp.py
@@ -221,6 +221,33 @@ def check(s, a=a, b=b):
     check('not a==b')
     if verbose: print "recursion tests ok"
 
+def dicts():
+    # Verify that __eq__ and __ne__ work for dicts even if the keys and
+    # values don't support anything other than __eq__ and __ne__.  Complex
+    # numbers are a fine example of that.
+    import random
+    imag1a = {}
+    for i in range(50):
+        imag1a[random.randrange(100)*1j] = random.randrange(100)*1j
+    items = imag1a.items()
+    random.shuffle(items)
+    imag1b = {}
+    for k, v in items:
+        imag1b[k] = v
+    imag2 = imag1b.copy()
+    imag2[k] = v + 1.0
+    verify(imag1a == imag1a, "imag1a == imag1a should have worked")
+    verify(imag1a == imag1b, "imag1a == imag1b should have worked")
+    verify(imag2 == imag2, "imag2 == imag2 should have worked")
+    verify(imag1a != imag2, "imag1a != imag2 should have worked")
+    for op in "<", "<=", ">", ">=":
+        try:
+            eval("imag1a %s imag2" % op)
+        except TypeError:
+            pass
+        else:
+            raise TestFailed("expected TypeError from imag1a %s imag2" % op)
+
 def main():
     basic()
     tabulate()
@@ -229,5 +256,6 @@ def main():
     testvector()
     misbehavin()
     recursion()
+    dicts()
 
 main()
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -17,14 +17,16 @@ Core
 
 - The following functions were generalized to work nicely with iterator
   arguments:
-    map(), filter(), reduce()
+    map(), filter(), reduce(), zip()
     list(), tuple() (PySequence_Tuple() and PySequence_Fast() in C API)
     max(), min()
-    zip()
     .join() method of strings
     'x in y' and 'x not in y' (PySequence_Contains() in C API)
     operator.countOf() (PySequence_Count() in C API)
 
+- Comparing dictionary objects via == and != is faster, and now works even
+  if the keys and values don't support comparisons other than ==.
+
 
 What's New in Python 2.1 (final)?
 =================================
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
@@ -1047,6 +1047,76 @@ dict_compare(dictobject *a, dictobject *b)
 	return res;
 }
 
+/* Return 1 if dicts equal, 0 if not, -1 if error.
+ * Gets out as soon as any difference is detected.
+ * Uses only Py_EQ comparison.
+ */
+static int
+dict_equal(dictobject *a, dictobject *b)
+{
+	int i;
+
+	if (a->ma_used != b->ma_used)
+		/* can't be equal if # of entries differ */
+		return 0;
+  
+	/* Same # of entries -- check all of 'em.  Exit early on any diff. */
+	for (i = 0; i < a->ma_size; i++) {
+		PyObject *aval = a->ma_table[i].me_value;
+		if (aval != NULL) {
+			int cmp;
+			PyObject *bval;
+			PyObject *key = a->ma_table[i].me_key;
+			/* temporarily bump aval's refcount to ensure it stays
+			   alive until we're done with it */
+			Py_INCREF(aval);
+			bval = PyDict_GetItem((PyObject *)b, key);
+			if (bval == NULL) {
+				Py_DECREF(aval);
+				return 0;
+			}
+			cmp = PyObject_RichCompareBool(aval, bval, Py_EQ);
+			Py_DECREF(aval);
+			if (cmp <= 0)  /* error or not equal */
+				return cmp;
+ 		}
+	}
+	return 1;
+ }
+
+static PyObject *
+dict_richcompare(PyObject *v, PyObject *w, int op)
+{
+	int cmp;
+	PyObject *res;
+
+	if (!PyDict_Check(v) || !PyDict_Check(w)) {
+		res = Py_NotImplemented;
+	}
+	else if (op == Py_EQ || op == Py_NE) {
+		cmp = dict_equal((dictobject *)v, (dictobject *)w);
+		if (cmp < 0)
+			return NULL;
+		res = (cmp == (op == Py_EQ)) ? Py_True : Py_False;
+	}
+	else {
+		cmp = dict_compare((dictobject *)v, (dictobject *)w);
+		if (cmp < 0 && PyErr_Occurred())
+			return NULL;
+		switch (op) {
+			case Py_LT: cmp = cmp <  0; break;
+			case Py_LE: cmp = cmp <= 0; break;
+			case Py_GT: cmp = cmp >  0; break;
+			case Py_GE: cmp = cmp >= 0; break;
+			default:
+				assert(!"op unexpected");
+		}
+		res = cmp ? Py_True : Py_False;
+	}
+	Py_INCREF(res);
+	return res;
+ }
+
 static PyObject *
 dict_has_key(register dictobject *mp, PyObject *args)
 {
@@ -1410,7 +1480,7 @@ PyTypeObject PyDict_Type = {
 	(printfunc)dict_print,			/* tp_print */
 	(getattrfunc)dict_getattr,		/* tp_getattr */
 	0,					/* tp_setattr */
-	(cmpfunc)dict_compare,			/* tp_compare */
+	0,					/* tp_compare */
 	(reprfunc)dict_repr,			/* tp_repr */
 	0,					/* tp_as_number */
 	&dict_as_sequence,			/* tp_as_sequence */
@@ -1425,7 +1495,7 @@ PyTypeObject PyDict_Type = {
 	0,					/* tp_doc */
 	(traverseproc)dict_traverse,		/* tp_traverse */
 	(inquiry)dict_tp_clear,			/* tp_clear */
-	0,					/* tp_richcompare */
+	dict_richcompare,			/* tp_richcompare */
 	0,					/* tp_weaklistoffset */
 	(getiterfunc)dict_iter,			/* tp_iter */
 	0,					/* tp_iternext */
