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BUG: Let CategoricalIndex take CategoricalDtype as dtype argument #18116

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Merged
merged 1 commit into from
Nov 5, 2017
Merged

BUG: Let CategoricalIndex take CategoricalDtype as dtype argument #18116

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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v0.21.1.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -119,7 +119,7 @@ Categorical
- Bug in :meth:`DataFrame.astype` where casting to 'category' on an empty ``DataFrame`` causes a segmentation fault (:issue:`18004`)
- Error messages in the testing module have been improved when items have
different ``CategoricalDtype`` (:issue:`18069`)
-
- ``CategoricalIndex`` can now correctly take a ``pd.api.types.CategoricalDtype`` as its dtype (:issue:`18116`)

Other
^^^^^
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3 changes: 2 additions & 1 deletion pandas/core/indexes/category.py
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Expand Up @@ -79,7 +79,8 @@ def __new__(cls, data=None, categories=None, ordered=None, dtype=None,
if data is not None or categories is None:
cls._scalar_data_error(data)
data = []
data = cls._create_categorical(cls, data, categories, ordered)
data = cls._create_categorical(cls, data, categories, ordered,
dtype)

if copy:
data = data.copy()
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25 changes: 25 additions & 0 deletions pandas/tests/indexes/test_category.py
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Expand Up @@ -4,6 +4,7 @@

import pandas.util.testing as tm
from pandas.core.indexes.api import Index, CategoricalIndex
from pandas.core.dtypes.dtypes import CategoricalDtype
from .common import Base

from pandas.compat import range, PY3
Expand Down Expand Up @@ -95,6 +96,11 @@ def test_construction(self):
1, -1, 0], dtype='int8'))
assert result.ordered

result = pd.CategoricalIndex(ci, categories=list('ab'), ordered=True)
expected = pd.CategoricalIndex(ci, categories=list('ab'), ordered=True,
dtype='category')
tm.assert_index_equal(result, expected, exact=True)

# turn me to an Index
result = Index(np.array(ci))
assert isinstance(result, Index)
Expand Down Expand Up @@ -125,6 +131,25 @@ def test_construction_with_dtype(self):
result = CategoricalIndex(idx, categories=idx, ordered=True)
tm.assert_index_equal(result, expected, exact=True)

def test_construction_with_categorical_dtype(self):
# construction with CategoricalDtype
# GH18109
data, cats, ordered = 'a a b b'.split(), 'c b a'.split(), True
dtype = CategoricalDtype(categories=cats, ordered=ordered)

result = pd.CategoricalIndex(data, dtype=dtype)
expected = pd.CategoricalIndex(data, categories=cats,
ordered=ordered)
tm.assert_index_equal(result, expected, exact=True)

# error to combine categories or ordered and dtype keywords args
with pytest.raises(ValueError, match="Cannot specify both `dtype` and "
"`categories` or `ordered`."):
pd.CategoricalIndex(data, categories=cats, dtype=dtype)
with pytest.raises(ValueError, match="Cannot specify both `dtype` and "
"`categories` or `ordered`."):
pd.CategoricalIndex(data, ordered=ordered, dtype=dtype)

def test_create_categorical(self):
# https://github.com/pandas-dev/pandas/pull/17513
# The public CI constructor doesn't hit this code path with
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