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Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440) #1456

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Merged
merged 4 commits into from
Oct 30, 2025
Merged

Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440) #1456

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fac9e80
Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440)
yusufcank34 Oct 29, 2025
dbfe078
Add isolated test for Index(DatetimeIndex) typing (GH#1440)
yusufcank34 Oct 29, 2025
773fdfc
Fix: Index(DatetimeIndex) now returns DatetimeIndex; consolidated tes…
yusufcank34 Oct 29, 2025
c5b0d15
Remove redundant test_datetime_index_1440.py and run pre-commit
yusufcank34 Oct 30, 2025
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14 changes: 13 additions & 1 deletion pandas-stubs/core/indexes/base.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -187,7 +187,9 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
@overload
def __new__(
cls,
data: Sequence[np.datetime64 | datetime] | IndexOpsMixin[datetime],
data: (
Sequence[np.datetime64 | datetime] | IndexOpsMixin[datetime] | DatetimeIndex
),
*,
dtype: TimestampDtypeArg = ...,
copy: bool = ...,
Expand Down Expand Up @@ -274,6 +276,16 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
name: Hashable = ...,
tupleize_cols: bool = ...,
) -> IntervalIndex[Interval[Any]]: ...
@overload
def __new__(
cls,
data: DatetimeIndex,
*,
dtype: TimestampDtypeArg | None = ...,
copy: bool = ...,
name: Hashable = ...,
tupleize_cols: bool = ...,
) -> DatetimeIndex: ...
# generic overloads
@overload
def __new__(
Expand Down
2 changes: 1 addition & 1 deletion tests/indexes/test_datetime_index.py
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Expand Up @@ -24,7 +24,7 @@ def test_index_relops() -> None:
)
x = pd.Timestamp("2022-01-17")
idx = check(
assert_type(pd.Index(data, name="date"), "pd.Index[pd.Timestamp]"), pd.Index
assert_type(pd.Index(data, name="date"), pd.DatetimeIndex), pd.DatetimeIndex
)
check(assert_type(data[x <= idx], pd.DatetimeIndex), pd.DatetimeIndex)
check(assert_type(data[x < idx], pd.DatetimeIndex), pd.DatetimeIndex)
Expand Down
8 changes: 8 additions & 0 deletions tests/indexes/test_datetime_index_1440.py
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@@ -0,0 +1,8 @@
from typing import assert_type
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Since there is already a test file for datetime index it is probably cleaner to consolidate your tests there (if we made one test file by issue it would quickly become overwhelming).
Another point is that you’d need to add check(assert_type(…), pd.DatetimeIndex) in top of the assertion you have already added here.

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@yusufcank34 Can you remove that file since it is already covered by the other test you modified? And run pre-commit before you push again, I will merge after it.

import pandas as pd

# GH#1440 – constructing Index from DatetimeIndex should return DatetimeIndex
data = pd.date_range("2022-01-01", "2022-01-03", freq="D")
idx = pd.Index(data, name="date")

assert_type(idx, pd.DatetimeIndex)
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