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DOC/TYP: index.take return val #40521

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May 23, 2021
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15 changes: 9 additions & 6 deletions pandas/core/indexes/base.py
Original file line number Diff line number Diff line change
Expand Up @@ -929,19 +929,20 @@ def astype(self, dtype, copy=True):

Parameters
----------
indices : list
indices : array-like
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i think Sequence[int] would be more helpful

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Happy to change, my only question would be if we want to be using type hints for user facing API. The numpy documentation for take just uses array_like

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i think Sequence[int] would be more helpful

we shouldn't use typing notation for docstrings. https://pandas.pydata.org/pandas-docs/dev/development/contributing_docstring.html#parameter-types

and from that guide...

If the exact type is not relevant, but must be compatible with a NumPy array, array-like can be specified. If Any type that can be iterated is accepted, iterable can be used:

but the guide doesn't mention sequence.

maybe sequence of int is allowed, but I think matching numpy is fine.

Indices to be taken.
axis : int, optional
The axis over which to select values, always 0.
allow_fill : bool, default True
fill_value : bool, default None
fill_value : scalar, default None
If allow_fill=True and fill_value is not None, indices specified by
-1 is regarded as NA. If Index doesn't hold NA, raise ValueError.
-1 are regarded as NA. If Index doesn't hold NA, raise ValueError.

Returns
-------
numpy.ndarray
Elements of given indices.
Index
An index formed of elements at the given indices. Will be the same
type as self, except for RangeIndex.

See Also
--------
Expand All @@ -950,7 +951,9 @@ def astype(self, dtype, copy=True):
"""

@Appender(_index_shared_docs["take"] % _index_doc_kwargs)
def take(self, indices, axis=0, allow_fill=True, fill_value=None, **kwargs):
def take(
self, indices, axis: int = 0, allow_fill: bool = True, fill_value=None, **kwargs
):
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Any advice on typing this return value? Can almost use the TypeVar _IndexT, but the problem is that RangeIndex.take returns a superclass (Int64Index).

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I think in the base class use Index, and can then use a typevar in the subclasses that do return the same type.

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I tried something along those lines originally - the problem I was running into is how to handle subclasses which rely on parent implementations. For example, for ExtensionIndex would like to be able to write a stub like

def take(
        self: _ExtensionIndexT,
        indices,
        axis: int = 0,
        allow_fill: bool = True,
        fill_value=None,
        **kwargs,
    ) -> _ExtensionIndexT: ...

to essentially type the child while still relying on the inherited implementation. But couldn't figure out a way to achieve this.

if kwargs:
nv.validate_take((), kwargs)
indices = ensure_platform_int(indices)
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