fixed Incorrect Exception comes with df.compare method #50083

Author: tpackard1

pandas/core/ops/__init__.py

@@ -313,7 +313,8 @@ def to_series(right):
                 left, right = left.align(right, join="outer", level=level, copy=False)
             else:
                 raise ValueError(
-                    "Can only compare identically-labeled DataFrame objects"
+                    "Can only compare identically-labeled (both index and columns)\
+                         DataFrame objects"
                 )
     elif isinstance(right, ABCSeries):
         # axis=1 is default for DataFrame-with-Series op

pandas/tests/frame/methods/test_compare.py

@@ -170,14 +170,16 @@ def test_compare_multi_index(align_axis):
 
 def test_compare_unaligned_objects():
     # test DataFrames with different indices
-    msg = "Can only compare identically-labeled DataFrame objects"
+    msg = "Can only compare identically-labeled (both index and columns) DataFrame\
+         objects"
     with pytest.raises(ValueError, match=msg):
         df1 = pd.DataFrame([1, 2, 3], index=["a", "b", "c"])
         df2 = pd.DataFrame([1, 2, 3], index=["a", "b", "d"])
         df1.compare(df2)
 
     # test DataFrames with different shapes
-    msg = "Can only compare identically-labeled DataFrame objects"
+    msg = "Can only compare identically-labeled (both index and columns) DataFrame\
+         objects"
     with pytest.raises(ValueError, match=msg):
         df1 = pd.DataFrame(np.ones((3, 3)))
         df2 = pd.DataFrame(np.zeros((2, 1)))

pandas/tests/frame/test_arithmetic.py

@@ -1536,7 +1536,8 @@ def test_comparisons(self, simple_frame, float_frame, func):
         result3 = func(float_frame, 0)
         tm.assert_numpy_array_equal(result3.values, func(float_frame.values, 0))
 
-        msg = "Can only compare identically-labeled DataFrame"
+        msg = "Can only compare identically-labeled (both index and columns)\
+             DataFrame objects"
         with pytest.raises(ValueError, match=msg):
             func(simple_frame, simple_frame[:2])
 

pandas/tests/frame/test_nonunique_indexes.py

@@ -203,7 +203,8 @@ def test_dup_columns_comparisons(self):
         df2 = DataFrame([[0, 1], [2, 4], [2, np.nan], [4, 5]], columns=["A", "A"])
 
         # not-comparing like-labelled
-        msg = "Can only compare identically-labeled DataFrame objects"
+        msg = "Can only compare identically-labeled (both index and columns) \
+            DataFrame objects"
         with pytest.raises(ValueError, match=msg):
             df1 == df2
 

pandas/tests/series/test_arithmetic.py

@@ -624,11 +624,15 @@ def test_ne(self):
     )
     def test_comp_ops_df_compat(self, left, right, frame_or_series):
         # GH 1134
-        msg = f"Can only compare identically-labeled {frame_or_series.__name__} objects"
+        # GH 50083 to clarify that index and columns must be identically labeled
         if frame_or_series is not Series:
+            msg = f"Can only compare identically-labeled (both index and columns)\
+                {frame_or_series.__name__} objects"
             left = left.to_frame()
             right = right.to_frame()
-
+        else:
+            msg = f"Can only compare identically-labeled {frame_or_series.__name__}\
+                 objects"
         with pytest.raises(ValueError, match=msg):
             left == right
         with pytest.raises(ValueError, match=msg):