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Merged
merged 15 commits into from
May 23, 2021
Merged

DOC/TYP: index.take return val #40521

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DOC/TYP: index.take
mzeitlin11 Mar 19, 2021
67b6299
Fix default
mzeitlin11 Mar 19, 2021
b609767
Update pandas/core/indexes/base.py
mzeitlin11 Mar 22, 2021
8b917de
Use AnyArrayLike instead of ArrayLike
mzeitlin11 Mar 22, 2021
eb6016a
Merge remote-tracking branch 'origin/master' into doc/index_take_meth
mzeitlin11 Mar 22, 2021
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Merge branch 'doc/index_take_meth' of github.com:/mzeitlin11/pandas i…
mzeitlin11 Mar 22, 2021
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Merge remote-tracking branch 'origin/master' into doc/index_take_meth
mzeitlin11 Mar 31, 2021
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Merge remote-tracking branch 'origin/master' into doc/index_take_meth
mzeitlin11 Apr 2, 2021
c37be8c
Remove complicated typing, doc fixes
mzeitlin11 Apr 2, 2021
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mzeitlin11 Apr 6, 2021
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Merge remote-tracking branch 'origin/master' into doc/index_take_meth
mzeitlin11 Apr 8, 2021
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mzeitlin11 Apr 23, 2021
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mzeitlin11 Apr 30, 2021
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mzeitlin11 May 11, 2021
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24 changes: 17 additions & 7 deletions pandas/core/indexes/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -886,7 +886,7 @@ def astype(self, dtype, copy=True):

Parameters
----------
indices : list
indices : array_like
Indices to be taken.
axis : int, optional
The axis over which to select values, always 0.
Expand All @@ -897,8 +897,8 @@ def astype(self, dtype, copy=True):

Returns
-------
numpy.ndarray
Elements of given indices.
Index
An index formed of elements at the given indices.

See Also
--------
Expand All @@ -907,16 +907,26 @@ 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: Union[ArrayLike, Sequence[int]],
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is ArrayLike really needed here? it should also be a Sequence[int]

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see #28770 for issue about EA, but applicable to Series, Index and np.ndarray also

from typing import Sequence, cast
import numpy as np
import pandas as pd
from pandas.core.arrays import ExtensionArray

df = pd.DataFrame({"a": [1, 2, 3]})
idx = df.index
arr: np.ndarray = cast(np.ndarray, idx._values)
ea: ExtensionArray = pd.array(arr, dtype="Int64")
ser = pd.Series(arr)
reveal_type(idx)
reveal_type(arr)
reveal_type(ea)
reveal_type(ser)


def func(arr: Sequence):
    pass


func(idx)
func(arr)
func(ea)
func(ser)

/home/simon/t.py:11: note: Revealed type is 'pandas.core.indexes.base.Index'
/home/simon/t.py:12: note: Revealed type is 'numpy.ndarray'
/home/simon/t.py:13: note: Revealed type is 'pandas.core.arrays.base.ExtensionArray'
/home/simon/t.py:14: note: Revealed type is 'pandas.core.series.Series'
/home/simon/t.py:21: error: Argument 1 to "func" has incompatible type "Index"; expected "Sequence[Any]"  [arg-type]
/home/simon/t.py:22: error: Argument 1 to "func" has incompatible type "ndarray"; expected "Sequence[Any]"  [arg-type]
/home/simon/t.py:23: error: Argument 1 to "func" has incompatible type "ExtensionArray"; expected "Sequence[Any]"  [arg-type]
/home/simon/t.py:24: error: Argument 1 to "func" has incompatible type "Series"; expected "Sequence[Any]"  [arg-type]

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)
allow_fill = self._maybe_disallow_fill(allow_fill, fill_value, indices)
indices_as_array = ensure_platform_int(indices)
allow_fill = self._maybe_disallow_fill(allow_fill, fill_value, indices_as_array)

# Note: we discard fill_value and use self._na_value, only relevant
# in the case where allow_fill is True and fill_value is not None
taken = algos.take(
self._values, indices, allow_fill=allow_fill, fill_value=self._na_value
self._values,
indices_as_array,
allow_fill=allow_fill,
fill_value=self._na_value,
)
return type(self)._simple_new(taken, name=self.name)

Expand Down