TheAlgorithms/Python · error · ValueError

surface_area_cube() only accepts non-negative values

Error message

surface_area_cube() only accepts non-negative values

What it means

surface_area_cube() raises this ValueError when side_length is negative, because a cube cannot have a negative edge length. The library validates domain constraints before computing 6 * side_length**2 and refuses to silently return a mathematically meaningless result. It is a deliberate input-domain guard, not a bug. Zero and positive floats/ints are accepted.

Source

Thrown at maths/area.py:27

def surface_area_cube(side_length: float) -> float:
    """
    Calculate the Surface Area of a Cube.

    >>> surface_area_cube(1)
    6
    >>> surface_area_cube(1.6)
    15.360000000000003
    >>> surface_area_cube(0)
    0
    >>> surface_area_cube(3)
    54
    >>> surface_area_cube(-1)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cube() only accepts non-negative values
    """
    if side_length < 0:
        raise ValueError("surface_area_cube() only accepts non-negative values")
    return 6 * side_length**2


def surface_area_cuboid(length: float, breadth: float, height: float) -> float:
    """
    Calculate the Surface Area of a Cuboid.

    >>> surface_area_cuboid(1, 2, 3)
    22
    >>> surface_area_cuboid(0, 0, 0)
    0
    >>> surface_area_cuboid(1.6, 2.6, 3.6)
    38.56
    >>> surface_area_cuboid(-1, 2, 3)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cuboid() only accepts non-negative values
    >>> surface_area_cuboid(1, -2, 3)

View on GitHub (pinned to f5988cc097)

Solutions

1. Inspect the value passed as side_length right before the call and fix the upstream sign error (e.g. swap the operands of the subtraction that produced it).
2. If a magnitude is intended, pass abs(side_length) or the correct positive measurement.
3. Validate numeric input at ingestion (reject or sanitize negatives) so the guard never fires.
4. Wrap the call in try/except ValueError only to convert it into a user-facing message.

Example fix

// before
area = surface_area_cube(edge)  # edge == -3 from bad input

# after
if edge < 0:
    raise ValueError(f"edge length must be >= 0, got {edge}")
area = surface_area_cube(edge)

if side_length < 0:
    raise ValueError(f'cube side must be >= 0, got {side_length}')
area = surface_area_cube(side_length)

def is_valid_cube_side(x: object) -> bool:
    return isinstance(x, (int, float)) and not isinstance(x, bool) and x >= 0

try:
    area = surface_area_cube(side_length)
except ValueError as e:
    raise ValueError(f'invalid cube input {side_length!r}: {e}') from e

When it happens

Trigger: Calling surface_area_cube(side_length) with side_length < 0, e.g. surface_area_cube(-1). Typically happens when the value comes from a subtraction like (a - b) that can go negative, or from unvalidated user/CSV input.

Common situations: Parsing measurements that use a minus sign as a placeholder for missing data; computing edge length as a difference of coordinates that flips sign; unit-conversion mistakes that negate the value.

Related errors

• surface_area_cuboid() only accepts non-negative values
• surface_area_sphere() only accepts non-negative values
• surface_area_hemisphere() only accepts non-negative values
• surface_area_cone() only accepts non-negative values
• surface_area_conical_frustum() only accepts non-negative val

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/7f9118b3b30b363d. Report an issue: GitHub.