TheAlgorithms/Python · error · ValueError

surface_area_cylinder() only accepts non-negative values

Error message

surface_area_cylinder() only accepts non-negative values

What it means

surface_area_cylinder() raises this ValueError when radius or height is negative. Both are physical dimensions enforced >= 0 before returning 2 * pi * r * (h + r). The guard exists because the formula would otherwise happily produce nonsense for negative inputs (or negative areas).

Source

Thrown at maths/area.py:201

    >>> surface_area_cylinder(0, 0)
    0.0
    >>> surface_area_cylinder(6, 8)
    527.7875658030853
    >>> surface_area_cylinder(-1, -2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cylinder() only accepts non-negative values
    >>> surface_area_cylinder(1, -2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cylinder() only accepts non-negative values
    >>> surface_area_cylinder(-1, 2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cylinder() only accepts non-negative values
    """
    if radius < 0 or height < 0:
        raise ValueError("surface_area_cylinder() only accepts non-negative values")
    return 2 * pi * radius * (height + radius)


def surface_area_torus(torus_radius: float, tube_radius: float) -> float:
    """Calculate the Area of a Torus.
    Wikipedia reference: https://en.wikipedia.org/wiki/Torus
    :return 4pi^2 * torus_radius * tube_radius
    >>> surface_area_torus(1, 1)
    39.47841760435743
    >>> surface_area_torus(4, 3)
    473.7410112522892
    >>> surface_area_torus(3, 4)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_torus() does not support spindle or self intersecting tori
    >>> surface_area_torus(1.6, 1.6)
    101.06474906715503
    >>> surface_area_torus(0, 0)

View on GitHub (pinned to f5988cc097)

Solutions

1. Assert or check radius >= 0 and height >= 0 before calling; fix the negative source.
2. For level-derived heights, clamp or reorder: height = abs(top - bottom).
3. Add min=0 constraints in UI forms or schema validators (pydantic Field(ge=0)).
4. Catch ValueError and re-raise with your application's error context.

Example fix

// before
area = surface_area_cylinder(r, h)  # h = level_a - level_b may be negative

# after
h = abs(level_a - level_b)
area = surface_area_cylinder(r, h)

if radius < 0 or height < 0:
    raise ValueError(f'cylinder dimensions must be >= 0: radius={radius}, height={height}')
area = surface_area_cylinder(radius, height)

def is_valid_cylinder(r: float, h: float) -> bool:
    return r >= 0 and h >= 0

try:
    area = surface_area_cylinder(radius, height)
except ValueError as e:
    raise ValueError(f'cylinder input rejected: {e}') from e

When it happens

Trigger: Calling surface_area_cylinder(radius, height) with radius < 0 or height < 0, e.g. surface_area_cylinder(-1, 2) or surface_area_cylinder(1, -2).

Common situations: Tank/pipe sizing code where height is computed as outlet_level - inlet_level and can go negative when sensors report out of order; user form input not restricted to positive numbers; importing from spreadsheets with negative placeholders.

Related errors

• surface_area_cube() only accepts non-negative values
• 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

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/8f3491f15033ad49. Report an issue: GitHub.