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DOC: add missing data handling info to pd.Categorical docstring #36125

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Sep 5, 2020
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DOC: add missing data handling info to pd.Categorical docstring #36125

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13 changes: 13 additions & 0 deletions pandas/core/arrays/categorical.py
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,19 @@ class Categorical(NDArrayBackedExtensionArray, PandasObject):
['a', 'b', 'c', 'a', 'b', 'c']
Categories (3, object): ['a', 'b', 'c']

Missing values are not included as a category.

>>> c = pd.Categorical([1, 2, 3, 1, 2, 3, np.nan])
>>> c
[1, 2, 3, 1, 2, 3, NaN]
Categories (3, int64): [1, 2, 3]

However, their presence is indicated in the `codes` attribute
by code `-1`.

>>> c.codes
array([ 0, 1, 2, 0, 1, 2, -1], dtype=int8)

Ordered `Categoricals` can be sorted according to the custom order
of the categories and can have a min and max value.

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