pandas.api.extensions.register_index_accessor#

pandas.api.extensions.register_index_accessor(name)[source]#

Register a custom accessor on Index objects.

Parameters:

namestr: Name under which the accessor should be registered. A warning is issued if this name conflicts with a preexisting attribute.

Returns:

callable: A class decorator.

See also

register_dataframe_accessor: Register a custom accessor on DataFrame objects.
register_series_accessor: Register a custom accessor on Series objects.
register_index_accessor: Register a custom accessor on Index objects.

Notes

This function allows you to register a custom-defined accessor class for Index. The requirements for the accessor class are as follows:

Must contain an init method that:
- accepts a single Index object
- raises an AttributeError if the Index object does not have correctly matching inputs for the accessor
Must contain a method for each access pattern.
- The methods should be able to take any argument signature.
- Accessible using the @property decorator if no additional arguments are needed.

Examples

An accessor that only accepts integers could have a class defined like this:

>>> @pd.api.extensions.register_index_accessor("int_accessor")
... class IntAccessor:
...     def __init__(self, pandas_obj):
...         if not all(isinstance(x, int) for x in pandas_obj):
...             raise AttributeError("The index must only be an integer value")
...         self._obj = pandas_obj
...
...     def even(self):
...         return [x for x in self._obj if x % 2 == 0]
>>> df = pd.DataFrame.from_dict(
...     {"row1": {"1": 1, "2": "a"}, "row2": {"1": 2, "2": "b"}}, orient="index"
... )
>>> df.index.int_accessor
Traceback (most recent call last):
...
AttributeError: The index must only be an integer value.
>>> df = pd.DataFrame(
...     {"col1": [1, 2, 3, 4], "col2": ["a", "b", "c", "d"]}, index=[1, 2, 5, 8]
... )
>>> df.index.int_accessor.even()
[2, 8]