BUG: Improve error message when transfrom() with incorrect axis (#58494)

Author: Zhengbo Wang

pandas/core/apply.py

@@ -628,7 +628,8 @@ def normalize_dictlike_arg(
 
             cols = Index(list(func.keys())).difference(obj.columns, sort=True)
             if len(cols) > 0:
-                raise KeyError(f"Column(s) {list(cols)} do not exist")
+                # GH 58474
+                raise KeyError(f"Label(s) {list(cols)} do not exist")
 
         aggregator_types = (list, tuple, dict)
 

pandas/tests/apply/test_invalid_arg.py

@@ -118,15 +118,15 @@ def test_dict_nested_renaming_depr(method):
 def test_missing_column(method, func):
     # GH 40004
     obj = DataFrame({"A": [1]})
-    match = re.escape("Column(s) ['B'] do not exist")
-    with pytest.raises(KeyError, match=match):
+    msg = r"Label\(s\) \['B'\] do not exist"
+    with pytest.raises(KeyError, match=msg):
         getattr(obj, method)(func)
 
 
 def test_transform_mixed_column_name_dtypes():
     # GH39025
     df = DataFrame({"a": ["1"]})
-    msg = r"Column\(s\) \[1, 'b'\] do not exist"
+    msg = r"Label\(s\) \[1, 'b'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         df.transform({"a": int, 1: str, "b": int})
 
@@ -359,3 +359,15 @@ def test_transform_reducer_raises(all_reductions, frame_or_series, op_wrapper):
     msg = "Function did not transform"
     with pytest.raises(ValueError, match=msg):
         obj.transform(op)
+
+
+def test_transform_missing_labels_raises():
+    # GH 58474
+    df = DataFrame({"foo": [2, 4, 6], "bar": [1, 2, 3]}, index=["A", "B", "C"])
+    msg = r"Label\(s\) \['A', 'B'\] do not exist"
+    with pytest.raises(KeyError, match=msg):
+        df.transform({"A": lambda x: x + 2, "B": lambda x: x * 2}, axis=0)
+
+    msg = r"Label\(s\) \['bar', 'foo'\] do not exist"
+    with pytest.raises(KeyError, match=msg):
+        df.transform({"foo": lambda x: x + 2, "bar": lambda x: x * 2}, axis=1)

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -5,7 +5,6 @@
 import datetime
 import functools
 from functools import partial
-import re
 
 import numpy as np
 import pytest
@@ -816,8 +815,8 @@ def test_agg_relabel_other_raises(self):
 
     def test_missing_raises(self):
         df = DataFrame({"A": [0, 1], "B": [1, 2]})
-        match = re.escape("Column(s) ['C'] do not exist")
-        with pytest.raises(KeyError, match=match):
+        msg = r"Label\(s\) \['C'\] do not exist"
+        with pytest.raises(KeyError, match=msg):
             df.groupby("A").agg(c=("C", "sum"))
 
     def test_agg_namedtuple(self):

pandas/tests/groupby/aggregate/test_other.py

@@ -209,7 +209,7 @@ def test_aggregate_api_consistency():
     expected = pd.concat([c_mean, c_sum, d_mean, d_sum], axis=1)
     expected.columns = MultiIndex.from_product([["C", "D"], ["mean", "sum"]])
 
-    msg = r"Column\(s\) \['r', 'r2'\] do not exist"
+    msg = r"Label\(s\) \['r', 'r2'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         grouped[["D", "C"]].agg({"r": "sum", "r2": "mean"})
 
@@ -224,7 +224,7 @@ def test_agg_dict_renaming_deprecation():
             {"B": {"foo": ["sum", "max"]}, "C": {"bar": ["count", "min"]}}
         )
 
-    msg = r"Column\(s\) \['ma'\] do not exist"
+    msg = r"Label\(s\) \['ma'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         df.groupby("A")[["B", "C"]].agg({"ma": "max"})
 

pandas/tests/resample/test_resample_api.py

@@ -328,7 +328,7 @@ def test_agg_consistency():
 
     r = df.resample("3min")
 
-    msg = r"Column\(s\) \['r1', 'r2'\] do not exist"
+    msg = r"Label\(s\) \['r1', 'r2'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         r.agg({"r1": "mean", "r2": "sum"})
 
@@ -343,7 +343,7 @@ def test_agg_consistency_int_str_column_mix():
 
     r = df.resample("3min")
 
-    msg = r"Column\(s\) \[2, 'b'\] do not exist"
+    msg = r"Label\(s\) \[2, 'b'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         r.agg({2: "mean", "b": "sum"})
 
@@ -534,7 +534,7 @@ def test_agg_with_lambda(cases, agg):
     ],
 )
 def test_agg_no_column(cases, agg):
-    msg = r"Column\(s\) \['result1', 'result2'\] do not exist"
+    msg = r"Label\(s\) \['result1', 'result2'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         cases[["A", "B"]].agg(**agg)
 
@@ -582,7 +582,7 @@ def test_agg_specificationerror_series(cases, agg):
 def test_agg_specificationerror_invalid_names(cases):
     # errors
     # invalid names in the agg specification
-    msg = r"Column\(s\) \['B'\] do not exist"
+    msg = r"Label\(s\) \['B'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         cases[["A"]].agg({"A": ["sum", "std"], "B": ["mean", "std"]})
 
@@ -631,7 +631,7 @@ def test_try_aggregate_non_existing_column():
     df = DataFrame(data).set_index("dt")
 
     # Error as we don't have 'z' column
-    msg = r"Column\(s\) \['z'\] do not exist"
+    msg = r"Label\(s\) \['z'\] do not exist"
     with pytest.raises(KeyError, match=msg):
         df.resample("30min").agg({"x": ["mean"], "y": ["median"], "z": ["sum"]})