TheAlgorithms/Python · warning · ValueError

Scores cannot be empty

Error message

Scores cannot be empty

What it means

A defensive tail raise at the end of casimir_force() in physics/casimir_effect.py (line 113). After the (force, area, distance).count(0) != 1 guard at the top, the if force==0 / elif area==0 / elif distance==0 chain is exhaustive for exactly-one-zero inputs, so this line is effectively unreachable: it exists so the function never implicitly returns None if the invariant is ever broken by future edits.

Source

Thrown at backtracking/minimax.py:58

    65
    >>> minimax(-1, 0, True, scores, height)
    Traceback (most recent call last):
        ...
    ValueError: Depth cannot be less than 0
    >>> minimax(0, 0, True, [], 2)
    Traceback (most recent call last):
        ...
    ValueError: Scores cannot be empty
    >>> scores = [3, 5, 2, 9, 12, 5, 23, 23]
    >>> height = math.log(len(scores), 2)
    >>> minimax(0, 0, True, scores, height)
    12
    """

    if depth < 0:
        raise ValueError("Depth cannot be less than 0")
    if len(scores) == 0:
        raise ValueError("Scores cannot be empty")

    # Base case: If the current depth equals the height of the tree,
    # return the score of the current node.
    if depth == height:
        return scores[node_index]

    # If it's the maximizer's turn, choose the maximum score
    # between the two possible moves.
    if is_max:
        return max(
            minimax(depth + 1, node_index * 2, False, scores, height),
            minimax(depth + 1, node_index * 2 + 1, False, scores, height),
        )

    # If it's the minimizer's turn, choose the minimum score
    # between the two possible moves.
    return min(
        minimax(depth + 1, node_index * 2, True, scores, height),

View on GitHub (pinned to f5988cc097)

Solutions

1. If you hit this, verify you are calling casimir_force with exactly one 0 — if that still fails, you are running modified library code.
2. Diff your local casimir_effect.py against upstream to find the edit that broke the invariant.
3. Restore the original file or fix the modified guard so count(0)==1 aligns with the branch chain.

try:
    result = casimir_force(force=f, area=a, distance=d)
except ValueError as e:
    # defensive tail raise: indicates modified library code
    raise RuntimeError("casimir_effect.py invariant broken; diff against upstream") from e

When it happens

Trigger: Not reachable through the public API as written. Would only fire if the top guard or the branch chain were modified (e.g. a refactor changes the count check but not the branches), or if a value compares != 0 but also != 0 in float terms (not possible for reals).

Common situations: You will essentially never see this at runtime; if you do, you are likely running a patched/forked version of casimir_effect.py where the validation chain was edited and became inconsistent.

Related errors

• Expected a_coeffs to have {self.order + 1} elements for {sel
• Expected b_coeffs to have {self.order + 1} elements for {sel
• k must not be negative
• n must not be negative
• Candidates list should not be empty

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/04f526c893cbbcd2. Report an issue: GitHub.