pola-rs/polars · error · TypeError

expected type 'int | str', got {qualified_type_name(item)!r}

Error message

expected type 'int | str', got {qualified_type_name(item)!r} ({item!r})

What it means

Error "expected type 'int | str', got {qualified_type_name(item)!r} ({item!r})" thrown in pola-rs/polars.

Source

Thrown at py-polars/src/polars/datatype_expr/struct.py:24

class DataTypeExprStructNameSpace:
    """Namespace for struct datatype expressions."""

    _accessor = "struct"

    def __init__(self, expr: pl.DataTypeExpr) -> None:
        self._pydatatype_expr = expr._pydatatype_expr

    def __getitem__(self, item: str | int) -> pl.DataTypeExpr:
        if isinstance(item, str):
            return self.field_dtype(item)
        elif isinstance(item, int):
            return pl.DataTypeExpr._from_pydatatype_expr(
                self._pydatatype_expr.struct_field_dtype_by_index(item)
            )
        else:
            msg = f"expected type 'int | str', got {qualified_type_name(item)!r} ({item!r})"
            raise TypeError(msg)

    def field_dtype(self, field_name: str) -> pl.DataTypeExpr:
        """

        Get the DataType of field with a specific field name.

        Notes
        -----
        The `struct` namespace has implemented `__getitem__` so you can also access
        fields by index:

        >>> (
        ...     pl.Struct({"x": pl.Int64, "y": pl.String})
        ...     .to_dtype_expr()
        ...     .struct[1]
        ...     .collect_dtype({})
        ... )
        String

View on GitHub (pinned to df599052da)

When it happens

Trigger: Thrown at py-polars/src/polars/datatype_expr/struct.py:24 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pola-rs/polars@df599052da (2026-08-16). Data as JSON: /api/errors/384f2c4f7b71ecf0. Report an issue: GitHub.