Merge pull request #23259 from oscarbenjamin/pr_unpickling_unyt_110

fix: add __setstate__ to support old pickles

sympy/core/basic.py

@@ -135,6 +135,10 @@ def __getnewargs__(self):
     def __getstate__(self):
         return None
 
+    def __setstate__(self, state):
+        for name, value in state.items():
+            setattr(self, name, value)
+
     def __reduce_ex__(self, protocol):
         if protocol < 2:
             msg = "Only pickle protocol 2 or higher is supported by SymPy"

sympy/utilities/tests/test_pickling.py

@@ -701,3 +701,14 @@ def test_deprecation_warning():
 
 def test_issue_18438():
     assert pickle.loads(pickle.dumps(S.Half)) == 1/2
+
+
+#================= old pickles =================
+def test_unpickle_from_older_versions():
+    data = (
+        b'\x80\x04\x95^\x00\x00\x00\x00\x00\x00\x00\x8c\x10sympy.core.power'
+        b'\x94\x8c\x03Pow\x94\x93\x94\x8c\x12sympy.core.numbers\x94\x8c'
+        b'\x07Integer\x94\x93\x94K\x02\x85\x94R\x94}\x94bh\x03\x8c\x04Half'
+        b'\x94\x93\x94)R\x94}\x94b\x86\x94R\x94}\x94b.'
+    )
+    assert pickle.loads(data) == sqrt(2)