pandas-dev/pandas · error · TypeError

Only list-like objects or None are allowed to be passed to s

Error message

Only list-like objects or None are allowed to be passed to safe_sort as codes

What it means

Raised by safe_sort when the codes argument is neither None nor list-like. codes must be an integer index array (or None) so that safe_sort can remap it to the sorted order; a scalar or dict is invalid.

Source

Thrown at pandas/core/algorithms.py:1730

        except (TypeError, decimal.InvalidOperation):
            # Previous sorters failed or were not applicable, try `_sort_mixed`
            # which would work, but which fails for special case of 1d arrays
            # with tuples.
            if values.size and isinstance(values[0], tuple):
                # error: Argument 1 to "_sort_tuples" has incompatible type
                # "Union[Index, ExtensionArray, ndarray[Any, Any]]"; expected
                # "ndarray[Any, Any]"
                ordered = _sort_tuples(values)  # type: ignore[arg-type]
            else:
                ordered = _sort_mixed(values)

    # codes:

    if codes is None:
        return ordered

    if not is_list_like(codes):
        raise TypeError(
            "Only list-like objects or None are allowed to "
            "be passed to safe_sort as codes"
        )
    codes = ensure_platform_int(np.asarray(codes))

    # ranks[i] gives the position of values[i] in `ordered`
    if use_counting:
        arr = cast("np.ndarray", values)
        if arr.dtype.kind == "i":
            # go through int64 so differences don't overflow narrower signed
            #  dtypes; int64 wraparound is exact since the true differences
            #  are within rng_size
            shifted = arr.astype(np.int64, copy=False) - vmin
        else:
            # unsigned: differences always fit the unsigned dtype
            shifted = arr - vmin
        present = np.zeros(rng_size, dtype=bool)
        present[shifted] = True

View on GitHub (pinned to 71959b8cb9)

Solutions

1. Pass an integer list/np.ndarray for codes, or None to skip remapping.
2. Wrap a single index in a list/array.
3. Validate codes with is_list_like before calling safe_sort.

Example fix

# before
pd.core.algorithms.safe_sort(np.array([1, 2, 3]), codes=2)
# after
pd.core.algorithms.safe_sort(np.array([1, 2, 3]), codes=np.array([2]))

import numpy as np
from pandas.api.types import is_list_like

def safe_sort_codes(codes):
    if codes is not None and not is_list_like(codes):
        raise TypeError('codes must be list-like or None')
    return None if codes is None else np.asarray(codes)

from pandas.api.types import is_list_like

def valid_codes(c) -> bool:
    return c is None or is_list_like(c)

When it happens

Trigger: safe_sort(values, codes=5) with a scalar; safe_sort(values, codes={0: 1}) with a dict; passing None incorrectly typed.

Common situations: Building the codes argument from a computation that accidentally yields a scalar; forwarding unvalidated user input as codes.

Related errors

• Only np.ndarray, ExtensionArray, and Index objects are allow
• values should be unique if codes is not None
• {func_name} requires a Series, Index, ExtensionArray, np.nda
• only list-like objects are allowed to be passed to isin(), y
• only list-like objects are allowed to be passed to isin(), y

AI-assisted analysis of pandas-dev/pandas@71959b8cb9 (2026-08-07). Data as JSON: /api/errors/8b08747ad0bab142. Report an issue: GitHub.