DOC/TST: Updated docstring to show method correctly and updated test

Author: aschade

doc/source/whatsnew/v0.23.0.txt

@@ -272,7 +272,7 @@ Other API Changes
 - :class:`IntervalIndex` and ``IntervalDtype`` no longer support categorical, object, and string subtypes (:issue:`19016`)
 - The default ``Timedelta`` constructor now accepts an ``ISO 8601 Duration`` string as an argument (:issue:`19040`)
 - ``IntervalDtype`` now returns ``True`` when compared against ``'interval'`` regardless of subtype, and ``IntervalDtype.name`` now returns ``'interval'`` regardless of subtype (:issue:`18980`)
-- ``KeyError`` now raises instead of ``ValueError`` when using :meth:`drop()` to remove a non-existent element in an axis of ``Series``, ``Index``, ``DataFrame`` and ``Panel`` (:issue:`19186`)
+- ``KeyError`` now raises instead of ``ValueError`` in :meth:`~DataFrame.drop`, :meth:`~Panel.drop`, :meth:`~Series.drop`, :meth:`~Index.drop` when dropping a non-existent element in an axis with duplicates (:issue:`19186`)
 - :func:`Series.to_csv` now accepts a ``compression`` argument that works in the same way as the ``compression`` argument in :func:`DataFrame.to_csv` (:issue:`18958`)
 
 .. _whatsnew_0230.deprecations:
@@ -416,7 +416,7 @@ Indexing
 - Bug in :func:`MultiIndex.set_labels` which would cause casting (and potentially clipping) of the new labels if the ``level`` argument is not 0 or a list like [0, 1, ... ]  (:issue:`19057`)
 - Bug in ``str.extractall`` when there were no matches empty :class:`Index` was returned instead of appropriate :class:`MultiIndex` (:issue:`19034`)
 - Bug in :class:`IntervalIndex` where set operations that returned an empty ``IntervalIndex`` had the wrong dtype (:issue:`19101`)
-- Bug in :func:`Index.drop()`, where no ``Exception`` is raised when dropping a non-existent element from an axis in ``Index`` (:issue:`19186`)
+- Bug in :meth:`~DataFrame.drop`, :meth:`~Panel.drop`, :meth:`~Series.drop`, :meth:`~Index.drop` where no ``KeyError`` is raised when dropping a non-existent element from an axis that contains duplicates (:issue:`19186`)
 -
 
 I/O

pandas/core/generic.py

@@ -2809,7 +2809,7 @@ def drop(self, labels=None, axis=0, index=None, columns=None, level=None,
         Raises
         ------
         KeyError
-            * If labels are not found in the selected axis
+            If none of the labels are found in the selected axis
 
         Examples
         --------

pandas/core/indexes/base.py

@@ -3764,7 +3764,7 @@ def drop(self, labels, errors='raise'):
         Raises
         ------
         KeyError
-            * If labels are not found in the selected axis
+            If none of the labels are found in the selected axis
         """
         arr_dtype = 'object' if self.dtype == 'object' else None
         labels = _index_labels_to_array(labels, dtype=arr_dtype)

pandas/tests/frame/test_axis_select_reindex.py

@@ -1143,6 +1143,7 @@ def test_raise_on_drop_duplicate_index(self, actual):
         level = 0 if isinstance(actual.index, MultiIndex) else None
         with pytest.raises(KeyError):
             actual.drop('c', level=level, axis=0)
+        with pytest.raises(KeyError):
             actual.T.drop('c', level=level, axis=1)
         expected_no_err = actual.drop('c', axis=0, level=level,
                                       errors='ignore')