pl.Expr.list.get raises error on null values.

[dalejung]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

    import polars as pl

    df = pl.DataFrame({
        'name': ['BOB-3', 'BOB', None],
    })

    split = df.with_columns(
        pl.col('name').str.split('-')
    )
    res = split.with_columns(pl.col('name').list.get(0))

Log output

No response

Issue description

Previously pl.Expr.list.get would propagate null values. Now it errors with ComputeError: get index is out of bounds.

Expected behavior

I would expect pl.Expr.list.get to not error on null list values.

Installed versions

--------Version info---------
Polars:               1.0.0-rc.2
Index type:           UInt32
Platform:             Linux-6.9.6-arch1-1-x86_64-with-glibc2.39
Python:               3.12.3 | packaged by conda-forge | (main, Apr 15 2024, 18:38:13) [GCC 12.3.0]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          3.0.0
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               2024.5.0
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               0.9.2.post8+g4cb29ba
matplotlib:           3.8.4
nest_asyncio:         1.6.0
numpy:                1.26.4
openpyxl:             3.1.2
pandas:               3.0.0.dev0+756.ge8e6be071c
pyarrow:              17.0.0.dev225+g72e7e4c6c
pydantic:             2.7.2
pyiceberg:            <not installed>
sqlalchemy:           <not installed>
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[lscheilling]

Wouldn't this error be related to the new null_on_oob parameter in pl.Expr.list.get?

Source Code

[mcrumiller]

I don't think that null values should raise on oob even when the parameter is True. If it did, the parameter would only be useful when dealing with series without nulls, otherwise it must be set to False. If not, all calls will fail as long as a single null value is present.

[mcrumiller]

Also, note that this is not the case for arrays:

s = pl.Series([None, [1]], dtype=pl.Array(pl.Int32, 1))
s.arr.get(0, null_on_oob=False)  # returns [null, 1]
s.arr.get(0, null_on_oob=True)   # returns [null, 1]

[stinodego]

Thanks for the report. This is most probably a side-effect of #16841

[stinodego]

Re-opening as this wasn't fixed completely - see #17276