Index.map(mapper, na_action=None, dtype=None, memory_scale=None, skip_infer=False)#

Map values using an input mapping or function.

  • mapper (function, dict, or Series) – Mapping correspondence.

  • na_action ({None, 'ignore'}) – If ‘ignore’, propagate NA values, without passing them to the mapping correspondence.


The output of the mapping function applied to the index. If the function returns a tuple with more than one element a MultiIndex will be returned.

Return type

Union[Index, MultiIndex]


>>> idx = pd.Index([1, 2, 3])  
>>> idx.map({1: 'a', 2: 'b', 3: 'c'})  
Index(['a', 'b', 'c'], dtype='object')

Using map with a function:

>>> idx = pd.Index([1, 2, 3])  
>>> idx.map('I am a {}'.format)  
Index(['I am a 1', 'I am a 2', 'I am a 3'], dtype='object')
>>> idx = pd.Index(['a', 'b', 'c'])  
>>> idx.map(lambda x: x.upper())  
Index(['A', 'B', 'C'], dtype='object')
dtypenp.dtype, default None

Specify return type of the function. Must be specified when we cannot decide the return type of the function.


Specify the scale of memory uses in the function versus input size.

skip_infer: bool, default False

Whether infer dtypes when dtypes or output_type is not specified

This docstring was copied from pandas.core.indexes.base.Index.