BUG: wrap __idiv__ to avoid making a copy (#12962)

Author: dkamm

pandas/core/ops.py

@@ -236,7 +236,7 @@ def f(self, other):
              __itruediv__=_wrap_inplace_method(new_methods["__truediv__"]),
              __ipow__=_wrap_inplace_method(new_methods["__pow__"]), ))
     if not compat.PY3:
-        new_methods["__idiv__"] = new_methods["__div__"]
+        new_methods["__idiv__"] = _wrap_inplace_method(new_methods["__div__"])
 
     add_methods(cls, new_methods=new_methods, force=force, select=select,
                 exclude=exclude)

pandas/tests/frame/test_operators.py

@@ -1161,6 +1161,21 @@ def test_inplace_ops_identity(self):
         assert_frame_equal(df2, expected)
         assert df._data is df2._data
 
+        # no id change
+        arr = np.array([1., 2., 3.])
+        df = DataFrame({'a': arr.copy()})
+        expected = id(df)
+        df += 2.
+        assert id(df) == expected
+        df -= 2.
+        assert id(df) == expected
+        df *= 2.
+        assert id(df) == expected
+        df /= 2.
+        assert id(df) == expected
+        df **= 2.
+        assert id(df) == expected
+
     def test_alignment_non_pandas(self):
         index = ['A', 'B', 'C']
         columns = ['X', 'Y', 'Z']