TheAlgorithms/Python · error · ValueError

abs_max_sort() arg is an empty sequence

Error message

abs_max_sort() arg is an empty sequence

What it means

Raised by abs_max_sort in maths/abs.py when called with an empty list. This variant sorts by absolute value and indexes [-1]; an empty sort has no last element, so the function raises ValueError up front rather than letting the [-1] index raise IndexError.

Source

Thrown at maths/abs.py:70

    for i in x:
        if abs(i) > abs(j):
            j = i
    return j


def abs_max_sort(x: list[int]) -> int:
    """
    >>> abs_max_sort([0,5,1,11])
    11
    >>> abs_max_sort([3,-10,-2])
    -10
    >>> abs_max_sort([])
    Traceback (most recent call last):
        ...
    ValueError: abs_max_sort() arg is an empty sequence
    """
    if len(x) == 0:
        raise ValueError("abs_max_sort() arg is an empty sequence")
    return sorted(x, key=abs)[-1]


def test_abs_val():
    """
    >>> test_abs_val()
    """
    assert abs_val(0) == 0
    assert abs_val(34) == 34
    assert abs_val(-100000000000) == 100000000000

    a = [-3, -1, 2, -11]
    assert abs_max(a) == -11
    assert abs_max_sort(a) == -11
    assert abs_min(a) == -1


if __name__ == "__main__":

View on GitHub (pinned to f5988cc097)

Solutions

1. Check emptiness before the call and handle the no-data case explicitly.
2. Repair upstream filtering/batching so empty inputs cannot reach this helper.
3. Prefer the O(n) abs_max unless you need the sort; both share the same empty-input contract.

Example fix

# before
m = abs_max_sort(items)  # items == []

# after
m = abs_max_sort(items) if items else None

if not items:
    return None
m = abs_max_sort(items)

def is_non_empty(seq) -> bool:
    return len(seq) > 0

When it happens

Trigger: Calling abs_max_sort([]) - the explicit len(x) == 0 guard fires before sorted(x, key=abs)[-1] is evaluated.

Common situations: Same shape as the other abs functions: empty filtered lists, empty batches, or aggregates over groups that turned out empty.

Related errors

• abs_min() arg is an empty sequence
• abs_max() arg is an empty sequence
• Limit for the Catalan sequence must be ≥ 0
• Number should not be negative.
• Negative arguments are not supported

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/8716d2ab15c05a5a. Report an issue: GitHub.