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Account for .loc[Scalar, list] in DataFrame #1109

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Account for .loc[Scalar, list] in DataFrame #1109

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61ea997
Account for `.loc[Scalar, list]` in DataFrame
carschandler Feb 7, 2025
0809031
Correct fix of `df.loc[int, [list, str]]`
carschandler Feb 10, 2025
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3 changes: 2 additions & 1 deletion pandas-stubs/core/frame.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -182,7 +182,8 @@ class _LocIndexerFrame(_LocIndexer, Generic[_T]):
| Callable[[DataFrame], IndexType | MaskType | Sequence[Hashable]]
| list[Hashable]
| tuple[
IndexType
int
| IndexType
Comment on lines +185 to +186
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This is the wrong place to make this change. You want it in the overload below that returns Series. You would have to add an overload in there for tuple[int | str, list[HashableT] to make it work.

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You're right. I was testing a different case and got confused. Thanks for the redirect. Will update.

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Do you think that tuple[Scalar, list[HashableT]] would be more appropriate?

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Yes, that should be fine.

Also, you should set up the pre-commit so things are properly formatted. See the output here:
https://github.com/pandas-dev/pandas-stubs/actions/runs/13202706637/job/36858930373?pr=1106

And instructions here for setting up your local testing environment:
https://github.com/pandas-dev/pandas-stubs/blob/main/docs/setup.md

then you can make sure that the changes you make don't break any existing tests

| MaskType
| list[HashableT]
| slice
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4 changes: 4 additions & 0 deletions tests/test_frame.py
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Expand Up @@ -3056,6 +3056,10 @@ def test_loclist() -> None:
check(assert_type(df.loc[:, [None]], pd.DataFrame), pd.DataFrame)
check(assert_type(df.loc[:, [1]], pd.DataFrame), pd.DataFrame)

def test_loc_int_row_strlist_col() -> None:
df = pd.DataFrame({"a": [1, 2], "b": [3, 4]})
check(assert_type(df.loc[0, ["a"]], pd.DataFrame), pd.DataFrame)
check(assert_type(df.loc[0, ["a", "b"]], pd.DataFrame), pd.DataFrame)
Comment on lines +3059 to +3062
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Should be this:

def test_loc_int_row_strlist_col() -> None:
    df = pd.DataFrame({"a": [1, 2], "b": [3, 4]})
    check(assert_type(df.loc[0, ["a"]], pd.Series), pd.Series)
    check(assert_type(df.loc[0, ["a", "b"]], pd.Series), pd.Series)

    df.index = pd.Index(["x", "y"])
    check(assert_type(df.loc["x", ["a"]], pd.Series), pd.Series)
    check(assert_type(df.loc["x", ["a", "b"]], pd.Series), pd.Series)

The results of these operations are Series not DataFrame. You also have to test a string as the first index as well.


def test_dict_items() -> None:
# GH 180
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