TheAlgorithms/Python · error · ValueError

area_circle() only accepts non-negative values

Error message

area_circle() only accepts non-negative values

What it means

area_circle() raises this ValueError when radius is negative. The library requires radius >= 0 before returning pi * radius**2. Because squaring would silently hide a negative input, the guard exists specifically to surface that mistake.

Source

Thrown at maths/area.py:451

def area_circle(radius: float) -> float:
    """
    Calculate the area of a circle.

    >>> area_circle(20)
    1256.6370614359173
    >>> area_circle(1.6)
    8.042477193189871
    >>> area_circle(0)
    0.0
    >>> area_circle(-1)
    Traceback (most recent call last):
        ...
    ValueError: area_circle() only accepts non-negative values
    """
    if radius < 0:
        raise ValueError("area_circle() only accepts non-negative values")
    return pi * radius**2


def area_ellipse(radius_x: float, radius_y: float) -> float:
    """
    Calculate the area of a ellipse.

    >>> area_ellipse(10, 10)
    314.1592653589793
    >>> area_ellipse(10, 20)
    628.3185307179587
    >>> area_ellipse(0, 0)
    0.0
    >>> area_ellipse(1.6, 2.6)
    13.06902543893354
    >>> area_ellipse(-10, 20)
    Traceback (most recent call last):
        ...

View on GitHub (pinned to f5988cc097)

Solutions

1. Validate radius >= 0 before the call and correct the upstream sign error.
2. Pass abs(radius) when the value is a magnitude with a sign artifact.
3. Restrict input types in forms/CLI (reject negatives at parse time).
4. Catch ValueError to emit a clear message.

Example fix

// before
area = area_circle(r)  # r = point_x - center_x, may be negative

# after
area = area_circle(abs(point_x - center_x))

if radius < 0:
    raise ValueError(f'circle radius must be >= 0, got {radius}')
area = area_circle(radius)

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

try:
    area = area_circle(radius)
except ValueError as e:
    raise ValueError(f'invalid circle radius {radius!r}: {e}') from e

When it happens

Trigger: Calling area_circle(radius) with radius < 0, e.g. area_circle(-1).

Common situations: Radius computed as a coordinate delta; user/CLI input not restricted to non-negative; data files where '-' marks missing entries.

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/24161d7027adffaa. Report an issue: GitHub.