Review (jreback)

Author: h-vetinari

pandas/core/frame.py

@@ -5215,8 +5215,10 @@ def update(self, other, join='left', overwrite=True, filter_func=None,
             If True, will raise a ValueError if the DataFrame and `other`
             both contain non-NA data in the same place.
         inplace : bool, default True
-            If True, follows the convention by ``dict`` of updating inplace. If
-            False, returns a new object.
+            If True, updates the DataFrame inplace. If False, returns a new
+            DataFrame.
+
+            .. versionadded:: 0.24.0
 
         Raises
         ------

pandas/tests/frame/test_combine_concat.py

@@ -212,14 +212,17 @@ def test_update(self, inplace):
 
         if inplace:
             df.update(other, inplace=inplace)
+            result = df
         else:
-            df = df.update(other, inplace=inplace)
+            orig = df.copy()
+            result = df.update(other, inplace=inplace)
+            assert_frame_equal(df, orig)
 
         expected = DataFrame([[1.5, nan, 3],
                               [3.6, 2, 3],
                               [1.5, nan, 3],
                               [1.5, nan, 7.]])
-        assert_frame_equal(df, expected)
+        assert_frame_equal(result, expected)
 
     def test_update_dtypes(self):