pola-rs/polars · error · TypeError

invalid input for `exclude` Expected one or more `str` or…

Error message

invalid input for `exclude`

Expected one or more `str` or `DataType`; found {item!r} instead.

What it means

The legacy cs.exclude() accepts only column-name strings, Polars DataTypes (including selectors internally), and iterables thereof. Any other item raises this TypeError with a message stating exactly what was found. Note this older exclude differs from the newer Selector.exclude/_combine_as_selector path.

Solutions

1. Pass only strings and/or Polars dtypes: cs.exclude('a', pl.UInt32).
2. Exclude by expression by switching to the newer API: cs.all().exclude(pl.col('a')) or df.select(cs.all() - cs.by_name('a')).
3. Convert indices to names: cs.exclude(*[df.columns[i] for i in idx]).
4. Pre-validate items: all(isinstance(x, (str, ...)) for x in items).

Example fix

// before
cs.exclude([pl.col("temp")])
// after
cs.exclude("temp")

import polars as pl
bad = [x for x in items if not isinstance(x, (str, pl.DataType))]
if bad:
    raise ValueError(f"exclude accepts only str/DataType, got: {bad!r}")

def is_exclude_item(x) -> bool:
    import polars as pl
    if isinstance(x, (str, pl.DataType)):
        return True
    return isinstance(x, (list, tuple, set)) and all(isinstance(i, (str, pl.DataType)) for i in x)

try:
    sel = cs.exclude(*items)
except TypeError as e:
    if "invalid input for `exclude`" in str(e):
        sel = cs.exclude(*(x for x in items if isinstance(x, str)))
    else:
        raise

When it happens

Trigger: cs.exclude(123), cs.exclude([pl.col('a')]) — expressions inside the collection, or None / arbitrary objects passed as items to exclude().

Common situations: Passing column indices instead of names; passing Exprs (allowed in newer code paths via _combine_as_selector but not here); None leaking from optional config.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• cannot parse input into Polars selector
• cannot turn into selector
• cannot turn into selector
• expected a selector; found
• expected one or more `str`, `DataType` or selector; found

AI-assisted analysis of pola-rs/polars@fe841f959e (2026-09-18). Data as JSON: /api/errors/b01d1921aebc54b7. Report an issue: GitHub.

Appendix: source

Thrown at py-polars/src/polars/selectors.py:578

        exclude_dtypes: builtins.list[PolarsDataType] = []
        for item in (
            *(
                columns
                if isinstance(columns, Collection) and not isinstance(columns, str)
                else [columns]
            ),
            *more_columns,
        ):
            if isinstance(item, str):
                exclude_cols.append(item)
            elif is_polars_dtype(item):
                exclude_dtypes.append(item)
            else:
                msg = (
                    "invalid input for `exclude`"
                    f"\n\nExpected one or more `str` or `DataType`; found {item!r} instead."
                )
                raise TypeError(msg)

        if exclude_cols and exclude_dtypes:
            msg = "cannot exclude by both column name and dtype"
            raise TypeError(msg)

        excluded = (
            by_dtype(exclude_dtypes)
            if exclude_dtypes
            else Selector._by_name(
                exclude_cols,
                strict=False,
                expand_patterns=True,
            )
        )
        return self - excluded

    def as_expr(self) -> Expr:
        """

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