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Classe « Categorical »

Méthode pandas.Categorical.map

Signature de la méthode map

def map(self, mapper, na_action: "Literal['ignore'] | None | lib.NoDefault" = <no_default>) 

Description

help(Categorical.map)

Map categories using an input mapping or function.

Maps the categories to new categories. If the mapping correspondence is
one-to-one the result is a :class:`~pandas.Categorical` which has the
same order property as the original, otherwise a :class:`~pandas.Index`
is returned. NaN values are unaffected.

If a `dict` or :class:`~pandas.Series` is used any unmapped category is
mapped to `NaN`. Note that if this happens an :class:`~pandas.Index`
will be returned.

Parameters
----------
mapper : function, dict, or Series
    Mapping correspondence.
na_action : {None, 'ignore'}, default 'ignore'
    If 'ignore', propagate NaN values, without passing them to the
    mapping correspondence.

    .. deprecated:: 2.1.0

       The default value of 'ignore' has been deprecated and will be changed to
       None in the future.

Returns
-------
pandas.Categorical or pandas.Index
    Mapped categorical.

See Also
--------
CategoricalIndex.map : Apply a mapping correspondence on a
    :class:`~pandas.CategoricalIndex`.
Index.map : Apply a mapping correspondence on an
    :class:`~pandas.Index`.
Series.map : Apply a mapping correspondence on a
    :class:`~pandas.Series`.
Series.apply : Apply more complex functions on a
    :class:`~pandas.Series`.

Examples
--------
>>> cat = pd.Categorical(['a', 'b', 'c'])
>>> cat
['a', 'b', 'c']
Categories (3, object): ['a', 'b', 'c']
>>> cat.map(lambda x: x.upper(), na_action=None)
['A', 'B', 'C']
Categories (3, object): ['A', 'B', 'C']
>>> cat.map({'a': 'first', 'b': 'second', 'c': 'third'}, na_action=None)
['first', 'second', 'third']
Categories (3, object): ['first', 'second', 'third']

If the mapping is one-to-one the ordering of the categories is
preserved:

>>> cat = pd.Categorical(['a', 'b', 'c'], ordered=True)
>>> cat
['a', 'b', 'c']
Categories (3, object): ['a' < 'b' < 'c']
>>> cat.map({'a': 3, 'b': 2, 'c': 1}, na_action=None)
[3, 2, 1]
Categories (3, int64): [3 < 2 < 1]

If the mapping is not one-to-one an :class:`~pandas.Index` is returned:

>>> cat.map({'a': 'first', 'b': 'second', 'c': 'first'}, na_action=None)
Index(['first', 'second', 'first'], dtype='object')

If a `dict` is used, all unmapped categories are mapped to `NaN` and
the result is an :class:`~pandas.Index`:

>>> cat.map({'a': 'first', 'b': 'second'}, na_action=None)
Index(['first', 'second', nan], dtype='object')

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