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BUG: DataFrame.drop raising TypeError when passing empty DatetimeIndex/list #28114

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BUG: DataFrame.drop raising TypeError when passing empty DatetimeIndex/list #28114

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3bf7b26
DataFrame.drop raising TypeError when passing empty DatetimeIndex/list
Aug 23, 2019
53566f6
Merge branch 'master' of https://github.com/pandas-dev/pandas into fi…
Aug 23, 2019
36d19f7
DOC: Update whatsnew
Aug 23, 2019
f32ed62
Small changes for PR #28114
Aug 24, 2019
3d7045c
Merge branch 'master' of https://github.com/pandas-dev/pandas into fi…
Aug 26, 2019
02bb501
Raise KeyError when passing str to DataFrame.drop
Aug 31, 2019
7009e2f
Merge branch 'master' of https://github.com/pandas-dev/pandas into fi…
Sep 3, 2019
25bf949
Made trivial changes for PR28114
Sep 3, 2019
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v1.0.0.rst
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Expand Up @@ -184,7 +184,7 @@ Groupby/resample/rolling
Reshaping
^^^^^^^^^

-
- Bug in :meth:`DataFrame.drop` when passing empty :class:`DatetimeIndex` or ``list`` (:issue:`27994`)
-

Sparse
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3 changes: 3 additions & 0 deletions pandas/core/generic.py
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Expand Up @@ -3916,6 +3916,9 @@ 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):
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rather than do this, you can just handle the empty case in _drop_axis

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Are you sure @jreback? I tried a little, but I couldn't get it work while making sure to raise KeyError when passing str/List[str] to DataFrame.drop() that has DatetimeIndex.

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I think the suggestion is to include the not len(labels) check in NDFrame._drop_axis. And when labels is empty we just return self from _drop_axis.

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can you try this

continue
obj = obj._drop_axis(labels, axis, level=level, errors=errors)

if inplace:
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4 changes: 4 additions & 0 deletions pandas/core/indexes/base.py
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Expand Up @@ -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:
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this likely is not necessary if you implemented as per my comment above

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When passing str, for example, to dataframe with DatetimeIndex, type(self) == type(target) would return False, in which case I believe KeyError should be raised. But underlying arrays aren't empty.
If not here, I feel like Cython code needs changing though I'm not confident.

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What exception do you get without this? Index.is_all_dates can be surprisingly expensive.

raise KeyError("{} not found in axis".format(target.to_numpy()))
tgt_values = target.asi8
else:
tgt_values = target._ndarray_values
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26 changes: 26 additions & 0 deletions pandas/tests/frame/test_axis_select_reindex.py
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Expand Up @@ -117,6 +117,32 @@ def test_drop(self):
df.drop(labels=df[df.b > 0].index, inplace=True)
assert_frame_equal(df, expected)

def test_drop_empty_index(self):
# GH 27994
df = pd.DataFrame(
{"a": [0, 1]},
index=[pd.Timestamp("2019-01-01"), pd.Timestamp("2019-01-01")],
)
result_empty_list = df.drop([])
assert_frame_equal(result_empty_list, df)

result_empty_array = df.drop(np.array([]))
assert_frame_equal(result_empty_array, df)

result_empty_index = df.drop(df[:0])
assert_frame_equal(result_empty_index, df)

@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
df = pd.DataFrame(
{"a": [0, 1]},
index=[pd.Timestamp("2019-01-01"), pd.Timestamp("2019-01-01")],
)
with pytest.raises(KeyError, match="not found in axis"):
df.drop(labels)

def test_drop_multiindex_not_lexsorted(self):
# GH 11640

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