TheAlgorithms/Python · error · ValueError

surface_area_cone() only accepts non-negative values

Error message

surface_area_cone() only accepts non-negative values

What it means

surface_area_cone() raises this ValueError when radius or height is negative. Both are physical dimensions of the cone; the library checks each before computing pi * r * (r + sqrt(h^2 + r^2)). Without the guard, a negative radius would silently return a negative area.

Source

Thrown at maths/area.py:134

    >>> surface_area_cone(1.6, 2.6)
    23.387862992395807
    >>> surface_area_cone(0, 0)
    0.0
    >>> surface_area_cone(-1, -2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cone() only accepts non-negative values
    >>> surface_area_cone(1, -2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cone() only accepts non-negative values
    >>> surface_area_cone(-1, 2)
    Traceback (most recent call last):
        ...
    ValueError: surface_area_cone() only accepts non-negative values
    """
    if radius < 0 or height < 0:
        raise ValueError("surface_area_cone() only accepts non-negative values")
    return pi * radius * (radius + (height**2 + radius**2) ** 0.5)


def surface_area_conical_frustum(
    radius_1: float, radius_2: float, height: float
) -> float:
    """
    Calculate the Surface Area of a Conical Frustum.

    >>> surface_area_conical_frustum(1, 2, 3)
    45.511728065337266
    >>> surface_area_conical_frustum(4, 5, 6)
    300.7913575056268
    >>> surface_area_conical_frustum(0, 0, 0)
    0.0
    >>> surface_area_conical_frustum(1.6, 2.6, 3.6)
    78.57907060751548
    >>> surface_area_conical_frustum(-1, 2, 3)

View on GitHub (pinned to f5988cc097)

Solutions

1. Verify both radius and height are >= 0 immediately before the call and fix whichever is negative.
2. If the values come from coordinates, normalize with abs(delta) before passing.
3. Use keyword arguments surface_area_cone(radius=..., height=...) to avoid order mistakes.
4. Catch ValueError to produce a domain-specific error message.

Example fix

// before
area = surface_area_cone(r, h)  # r or h may be negative deltas

# after
r, h = abs(r), abs(h)
area = surface_area_cone(radius=r, height=h)

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

def is_valid_cone_dims(radius: float, height: float) -> bool:
    return radius >= 0 and height >= 0

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

When it happens

Trigger: Calling surface_area_cone(radius, height) with radius < 0 or height < 0, e.g. surface_area_cone(-1, 2) or surface_area_cone(1, -2). Argument order confusion (passing height where radius belongs) with signed values also triggers it.

Common situations: Mixing up positional arguments when refactoring to keyword style; heights computed as top - bottom with reversed coordinates; measurement imports containing negative sentinels.

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_conical_frustum() only accepts non-negative val

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/2d5124d582f9732d. Report an issue: GitHub.