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BUG: Don't cast categorical nan to int #28438

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Merged
merged 18 commits into from
Sep 18, 2019
Merged

BUG: Don't cast categorical nan to int #28438

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9dd2dbe
Don't cast categorical nan to int
Sep 12, 2019
952114f
Parametrize test
Sep 13, 2019
ffed8a0
Add CategoricalIndex test
Sep 14, 2019
504be90
Use isfinite
Sep 14, 2019
1290cb2
Fix
Sep 14, 2019
ab21763
Check TypeError as well for now
Sep 14, 2019
858ff06
Check error message
Sep 15, 2019
88874dc
Fix doc typo
Sep 15, 2019
eb76e1f
Revert "Use isfinite"
Sep 15, 2019
2a8186a
Extract array directly
Sep 15, 2019
afacbe3
Keep _maybe_promote
Sep 15, 2019
dbff36f
Add note
Sep 15, 2019
075ba33
Fix typo
Sep 15, 2019
5aeb8b6
Update doc/source/whatsnew/v1.0.0.rst
dsaxton Sep 16, 2019
af3ff15
Use np.asarray
Sep 16, 2019
e9cc1fa
Only check NaN
Sep 16, 2019
ab7b3ce
Change error message
Sep 17, 2019
754a3ed
Add to test cases
Sep 17, 2019
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.0.0.rst
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Expand Up @@ -110,6 +110,7 @@ Categorical
^^^^^^^^^^^

- Added test to assert the :func:`fillna` raises the correct ValueError message when the value isn't a value from categories (:issue:`13628`)
- Bug in :meth:`Categorical.astype` where ``NaN`` values were handled incorrectly when casting to int (:issue:`28406`)
-
-

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3 changes: 3 additions & 0 deletions pandas/core/arrays/categorical.py
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Expand Up @@ -520,6 +520,9 @@ def astype(self, dtype: Dtype, copy: bool = True) -> ArrayLike:
if dtype == self.dtype:
return self
return self._set_dtype(dtype)
if is_integer_dtype(dtype) and self.isna().any():
msg = "Cannot convert float NaN to integer"
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Kinda pedantic, but we can have other NA values here.

In [18]: cat = pd.Categorical([pd.Timestamp('2000'), pd.NaT])

In this case, it's not a float that we're refusing to cast. So perhaps Cannot convert NA to integer.

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Agree this seems more correct; do we want to think about consistency with Series as @jreback pointed out above? Incidentally I just noticed that Series seems to be misbehaving as well in this special case, so probably worth a separate issue or PR:

[ins] In [5]: pd.Series([pd.Timestamp("2000"), pd.NaT]).astype(int)             
Out[5]: 
0     946684800000000000
1   -9223372036854775808
dtype: int64

raise ValueError(msg)
return np.array(self, dtype=dtype, copy=copy)

@cache_readonly
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8 changes: 4 additions & 4 deletions pandas/core/indexes/base.py
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Expand Up @@ -4713,13 +4713,13 @@ def set_value(self, arr, key, value):
@Appender(_index_shared_docs["get_indexer_non_unique"] % _index_doc_kwargs)
def get_indexer_non_unique(self, target):
target = ensure_index(target)
if is_categorical(target):
target = target.astype(target.dtype.categories.dtype)
pself, ptarget = self._maybe_promote(target)
if pself is not self or ptarget is not target:
return pself.get_indexer_non_unique(ptarget)

if self.is_all_dates:
if is_categorical(target):
tgt_values = np.asarray(target)
elif self.is_all_dates:
tgt_values = target.asi8
else:
tgt_values = target._ndarray_values
Expand All @@ -4731,7 +4731,7 @@ def get_indexer_for(self, target, **kwargs):
"""
Guaranteed return of an indexer even when non-unique.

This dispatches to get_indexer or get_indexer_nonunique
This dispatches to get_indexer or get_indexer_non_unique
as appropriate.

Returns
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12 changes: 10 additions & 2 deletions pandas/tests/extension/test_categorical.py
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Expand Up @@ -19,7 +19,7 @@
import pytest

import pandas as pd
from pandas import Categorical
from pandas import Categorical, CategoricalIndex, Timestamp
from pandas.api.types import CategoricalDtype
from pandas.tests.extension import base
import pandas.util.testing as tm
Expand Down Expand Up @@ -197,7 +197,15 @@ def test_searchsorted(self, data_for_sorting):


class TestCasting(base.BaseCastingTests):
pass
@pytest.mark.parametrize("cls", [Categorical, CategoricalIndex])
@pytest.mark.parametrize("values", [[1, np.nan], [Timestamp("2000"), pd.NaT]])
def test_cast_nan_to_int(self, cls, values):
# GH 28406
s = cls(values)

msg = "Cannot (cast|convert)"
with pytest.raises((ValueError, TypeError), match=msg):
s.astype(int)


class TestArithmeticOps(base.BaseArithmeticOpsTests):
Expand Down