BUG: correct wrong error message in df.pivot when columns=None (#30925)

Author: charlesdong1991

doc/source/whatsnew/v1.1.0.rst

@@ -142,6 +142,7 @@ Reshaping
 
 -
 - Bug in :meth:`DataFrame.pivot_table` when only MultiIndexed columns is set (:issue:`17038`)
+- Fix incorrect error message in :meth:`DataFrame.pivot` when ``columns`` is set to ``None``. (:issue:`30924`)
 - Bug in :func:`crosstab` when inputs are two Series and have tuple names, the output will keep dummy MultiIndex as columns. (:issue:`18321`)
 
 

pandas/core/reshape/pivot.py

@@ -429,6 +429,9 @@ def _convert_by(by):
 @Substitution("\ndata : DataFrame")
 @Appender(_shared_docs["pivot"], indents=1)
 def pivot(data: "DataFrame", index=None, columns=None, values=None) -> "DataFrame":
+    if columns is None:
+        raise TypeError("pivot() missing 1 required argument: 'columns'")
+
     if values is None:
         cols = [columns] if index is None else [index, columns]
         append = index is None

pandas/tests/reshape/test_pivot.py

@@ -781,6 +781,15 @@ def test_pivot_with_list_like_values_nans(self, values, method):
         expected = DataFrame(data=data, index=index, columns=columns, dtype="object")
         tm.assert_frame_equal(result, expected)
 
+    def test_pivot_columns_none_raise_error(self):
+        # GH 30924
+        df = pd.DataFrame(
+            {"col1": ["a", "b", "c"], "col2": [1, 2, 3], "col3": [1, 2, 3]}
+        )
+        msg = r"pivot\(\) missing 1 required argument: 'columns'"
+        with pytest.raises(TypeError, match=msg):
+            df.pivot(index="col1", values="col3")
+
     @pytest.mark.xfail(
         reason="MultiIndexed unstack with tuple names fails with KeyError GH#19966"
     )