Raise KeyError when passing str to DataFrame.drop

* Handle str passed to DataFrame.drop() when dataframe has DatetimeIndex * Add comments * Fix whatsnew

doc/source/whatsnew/v1.0.0.rst

@@ -208,7 +208,7 @@ Other
 ^^^^^
 - Trying to set the ``display.precision``, ``display.max_rows`` or ``display.max_columns`` using :meth:`set_option` to anything but a ``None`` or a positive int will raise a ``ValueError`` (:issue:`23348`)
 - :meth:`DataFrame.to_csv` and :meth:`Series.to_csv` now support dicts as ``compression`` argument with key ``'method'`` being the compression method and others as additional compression options when the compression method is ``'zip'``. (:issue:`26023`)
-- Bug in :meth:`DataFrame.drop` when passing empty :meth:`DatetimeIndex` or `list`
+- Bug in :meth:`DataFrame.drop` when passing empty :class:`DatetimeIndex` or ``list`` (:issue:`27994`)
 
 
 .. _whatsnew_1000.contributors:

pandas/core/generic.py

@@ -3915,6 +3915,7 @@ def drop(
 
  for axis, labels in axes.items():
  if labels is not None:
+ # Check for empty Index, GH 27994
  if is_list_like(labels) and not len(labels):
  continue
  obj = obj._drop_axis(labels, axis, level=level, errors=errors)

pandas/core/indexes/base.py

@@ -4720,6 +4720,10 @@ def get_indexer_non_unique(self, target):
  return pself.get_indexer_non_unique(ptarget)
 
  if self.is_all_dates:
+ # If `target` doesn't consist of dates, `target.asi8` will return
+ # None, which will raise TypeError. GH 27994
+ if not target.is_all_dates:
+ raise KeyError("{} not found in axis".format(target.to_numpy()))
  tgt_values = target.asi8
  else:
  tgt_values = target._ndarray_values

pandas/tests/frame/test_axis_select_reindex.py

@@ -127,6 +127,16 @@ def test_drop_empty_index(self):
  assert_frame_equal(df_index.drop(np.array([])), df_index)
  assert_frame_equal(df_index.drop(df_index[:0]), df_index)
 
+ @pytest.mark.parametrize("labels", ["a", ["a"]])
+ def test_drop_empty_index_str(self, labels):
+ # Passing str to DataFrame.drop() for dataframe with DatetimeIndex
+ # should raise KeyError, GH 27994
+ with pytest.raises(KeyError, match="not found in axis"):
+ pd.DataFrame(
+ {"a": [0, 1]},
+ index=[pd.Timestamp("2019-01-01"), pd.Timestamp("2019-01-01")],
+ ).drop(labels)
+
  def test_drop_multiindex_not_lexsorted(self):
  # GH 11640