GH-99155: Fix NormalDist pickle with 0 and 1 protocols (GH99156)

Author: sobolevn

Lib/statistics.py

@@ -1446,3 +1446,9 @@ def __hash__(self):
 
     def __repr__(self):
         return f'{type(self).__name__}(mu={self._mu!r}, sigma={self._sigma!r})'
+
+    def __getstate__(self):
+        return self._mu, self._sigma
+
+    def __setstate__(self, state):
+        self._mu, self._sigma = state

Lib/test/test_statistics.py

@@ -3003,14 +3003,19 @@ def __init__(self, mu, sigma):
         nd = NormalDist(100, 15)
         self.assertNotEqual(nd, lnd)
 
-    def test_pickle_and_copy(self):
+    def test_copy(self):
         nd = self.module.NormalDist(37.5, 5.625)
         nd1 = copy.copy(nd)
         self.assertEqual(nd, nd1)
         nd2 = copy.deepcopy(nd)
         self.assertEqual(nd, nd2)
-        nd3 = pickle.loads(pickle.dumps(nd))
-        self.assertEqual(nd, nd3)
+
+    def test_pickle(self):
+        nd = self.module.NormalDist(37.5, 5.625)
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(proto=proto):
+                pickled = pickle.loads(pickle.dumps(nd, protocol=proto))
+                self.assertEqual(nd, pickled)
 
     def test_hashability(self):
         ND = self.module.NormalDist

Misc/NEWS.d/next/Library/2022-11-06-12-44-51.gh-issue-99155.vLZOzi.rst

@@ -0,0 +1 @@
+Fix :class:`statistics.NormalDist` pickle with ``0`` and ``1`` protocols.