TheAlgorithms/Python · error · ValueError

area_ellipse() only accepts non-negative values

Error message

area_ellipse() only accepts non-negative values

What it means

area_ellipse() raises this ValueError when radius_x or radius_y is negative. Semi-axes are physical lengths; the library enforces >= 0 before returning pi * radius_x * radius_y. This also prevents the classic bug where two negatives multiply into a plausible-looking but wrong area.

Source

Thrown at maths/area.py:481

    >>> area_ellipse(0, 0)
    0.0
    >>> area_ellipse(1.6, 2.6)
    13.06902543893354
    >>> area_ellipse(-10, 20)
    Traceback (most recent call last):
        ...
    ValueError: area_ellipse() only accepts non-negative values
    >>> area_ellipse(10, -20)
    Traceback (most recent call last):
        ...
    ValueError: area_ellipse() only accepts non-negative values
    >>> area_ellipse(-10, -20)
    Traceback (most recent call last):
        ...
    ValueError: area_ellipse() only accepts non-negative values
    """
    if radius_x < 0 or radius_y < 0:
        raise ValueError("area_ellipse() only accepts non-negative values")
    return pi * radius_x * radius_y


def area_rhombus(diagonal_1: float, diagonal_2: float) -> float:
    """
    Calculate the area of a rhombus.

    >>> area_rhombus(10, 20)
    100.0
    >>> area_rhombus(1.6, 2.6)
    2.08
    >>> area_rhombus(0, 0)
    0.0
    >>> area_rhombus(-1, -2)
    Traceback (most recent call last):
        ...
    ValueError: area_rhombus() only accepts non-negative values
    >>> area_rhombus(1, -2)

View on GitHub (pinned to f5988cc097)

Solutions

1. Validate both radii >= 0 before calling; fix the negative source.
2. Normalize signed extents to magnitudes with abs().
3. Clean imported datasets before computation.
4. Catch ValueError and report both values.

Example fix

// before
area = area_ellipse(rx, ry)  # rx = x_max - x_min style delta may be < 0

# after
area = area_ellipse(abs(rx), abs(ry))

if radius_x < 0 or radius_y < 0:
    raise ValueError(f'ellipse semi-axes must be >= 0: {radius_x}, {radius_y}')
area = area_ellipse(radius_x, radius_y)

def is_valid_semi_axes(rx: float, ry: float) -> bool:
    return rx >= 0 and ry >= 0

try:
    area = area_ellipse(radius_x, radius_y)
except ValueError as e:
    raise ValueError(f'invalid ellipse input: {e}') from e

When it happens

Trigger: Calling area_ellipse(radius_x, radius_y) with either argument < 0, e.g. area_ellipse(10, -20) or area_ellipse(-10, -20).

Common situations: Semi-axes taken from orbital/elliptical data with signed conventions; coordinate-derived extents where a direction flips sign; imported data with 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_cone() only accepts non-negative values

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/d2bbe614b1dde844. Report an issue: GitHub.