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Type hint warning for Polars List/Array in Column dtype #2172

@chapmacl

Description

@chapmacl

Describe the bug
My goal is to create a DataFrameSchema which has a Column of type List/Array with a defined inner type. This works fine if I simply use dtype=pl.List but then I am unsure how to define the inner type.

I could write dtype=pl.List(pl.Int64), which works when I call .validate() and it behaves normally but dtype expects PolarsDtypeInputTypes, ie str | type | pl.datatypes.classes.DataTypeClass | None and this trips up my linter.

Maybe I am doing this incorrectly but I couldn't find any additional information on how to accomplish this and I want to be able to use this feature without needed # type: ignore[arg-type] all over my code.

  • I have checked that this issue has not already been reported.
  • I have confirmed this bug exists on the latest version of pandera.
  • (optional) I have confirmed this bug exists on the main branch of pandera.

Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.

Code Sample, a copy-pastable example

import polars as pl
import pandera.polars as pa

column1 = pa.Column(
    name="column1",
    dtype=pl.Int64
)

column2 = pa.Column(
    name="column2",
    dtype=pl.List(pl.Int64), # Type Warning
)

schema = pa.DataFrameSchema(
    columns={
        column1.name: column1,
        column2.name: column2
    }
)

df = pl.DataFrame(
    {
        column1.name: [1,2],
        column2.name: [[1], [2]]
    }
)

schema.validate(df)

Expected behavior

The possibility to create a List/Array Column and define the inner Datatype without a Type Hint Warning

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