Add __reduce__ method to ExtensionType class

Author: AlenkaF

python/pyarrow/tests/test_extension_type.py

@@ -867,6 +867,13 @@ def test_generic_ext_type_equality():
     assert not period_type == period_type3
 
 
+def test_generic_ext_type_pickling():
+    # GH-36038
+    period_type = PeriodType('D')
+    period_type_pickled = pickle.loads(pickle.dumps(period_type))
+    assert period_type == period_type_pickled
+
+
 def test_generic_ext_type_register(registered_period_type):
     # test that trying to register other type does not segfault
     with pytest.raises(TypeError):

python/pyarrow/types.pxi

@@ -1487,6 +1487,9 @@ cdef class ExtensionType(BaseExtensionType):
         """
         return NotImplementedError
 
+    def __reduce__(self):
+        return self.__arrow_ext_deserialize__, (self.storage_type, self.__arrow_ext_serialize__())
+
     def __arrow_ext_class__(self):
         """Return an extension array class to be used for building or
         deserializing arrays with this extension type.