diff --git a/pandas/tests/copy_view/test_methods.py b/pandas/tests/copy_view/test_methods.py index 0a668ca4bf90e..c20176f57f482 100644 --- a/pandas/tests/copy_view/test_methods.py +++ b/pandas/tests/copy_view/test_methods.py @@ -1529,6 +1529,42 @@ def test_xs_multiindex(using_copy_on_write, using_array_manager, key, level, axi tm.assert_frame_equal(df, df_orig) +def test_update_frame(using_copy_on_write): + df1 = DataFrame({"a": [1.0, 2.0, 3.0], "b": [4.0, 5.0, 6.0]}) + df2 = DataFrame({"b": [100.0]}, index=[1]) + df1_orig = df1.copy() + view = df1[:] + + df1.update(df2) + + expected = DataFrame({"a": [1.0, 2.0, 3.0], "b": [4.0, 100.0, 6.0]}) + tm.assert_frame_equal(df1, expected) + if using_copy_on_write: + # df1 is updated, but its view not + tm.assert_frame_equal(view, df1_orig) + assert np.shares_memory(get_array(df1, "a"), get_array(view, "a")) + assert not np.shares_memory(get_array(df1, "b"), get_array(view, "b")) + else: + tm.assert_frame_equal(view, expected) + + +def test_update_series(using_copy_on_write): + ser1 = Series([1.0, 2.0, 3.0]) + ser2 = Series([100.0], index=[1]) + ser1_orig = ser1.copy() + view = ser1[:] + + ser1.update(ser2) + + expected = Series([1.0, 100.0, 3.0]) + tm.assert_series_equal(ser1, expected) + if using_copy_on_write: + # ser1 is updated, but its view not + tm.assert_series_equal(view, ser1_orig) + else: + tm.assert_series_equal(view, expected) + + def test_inplace_arithmetic_series(): ser = Series([1, 2, 3]) data = get_array(ser)