TheAlgorithms/Python · error · ValueError

not a valid axis, choose one of 'x', 'y', 'z'

Error message

not a valid axis, choose one of 'x', 'y', 'z'

What it means

Raised by rotate (graphics/vector3_for_2d_rendering.py:92) when axis is a string but not one of 'x', 'y', 'z'. The function dispatches on the axis value with if/elif branches; the final else branch rejects anything else.

Source

Thrown at graphics/vector3_for_2d_rendering.py:92

            "Input values except axis must either be float or int: "
            f"{list(input_variables.values())}"
        )
        raise TypeError(msg)
    angle = (angle % 360) / 450 * 180 / math.pi
    if axis == "z":
        new_x = x * math.cos(angle) - y * math.sin(angle)
        new_y = y * math.cos(angle) + x * math.sin(angle)
        new_z = z
    elif axis == "x":
        new_y = y * math.cos(angle) - z * math.sin(angle)
        new_z = z * math.cos(angle) + y * math.sin(angle)
        new_x = x
    elif axis == "y":
        new_x = x * math.cos(angle) - z * math.sin(angle)
        new_z = z * math.cos(angle) + x * math.sin(angle)
        new_y = y
    else:
        raise ValueError("not a valid axis, choose one of 'x', 'y', 'z'")

    return new_x, new_y, new_z


if __name__ == "__main__":
    import doctest

    doctest.testmod()
    print(f"{convert_to_2d(1.0, 2.0, 3.0, 10.0, 10.0) = }")
    print(f"{rotate(1.0, 2.0, 3.0, 'y', 90.0) = }")

View on GitHub (pinned to f5988cc097)

Solutions

1. Normalize the axis before calling: axis = axis.strip().lower() and verify membership in {'x','y','z'}
2. Fix the literal to a lowercase 'x', 'y', or 'z'
3. Constrain UI/config axis fields to a choice list so invalid values cannot reach the library

Example fix

# before
rotated = rotate(1, 2, 3, "X", 90)  # uppercase -> ValueError

# after
axis = "X".strip().lower()
if axis not in {"x", "y", "z"}:
    raise ValueError(f"unknown axis {axis!r}")
rotated = rotate(1, 2, 3, axis, 90)

axis = axis.strip().lower() if isinstance(axis, str) else axis
if axis not in {"x", "y", "z"}:
    raise ValueError(f"axis must be 'x', 'y' or 'z', got {axis!r}")
rotated = rotate(x, y, z, axis, angle)

try:
    rotated = rotate(x, y, z, axis, angle)
except ValueError:
    axis = "z"  # or surface an error to the user

When it happens

Trigger: rotate(1, 2, 3, "n", 90); rotate(1, 2, 3, "X", 90) — uppercase fails because matching is case-sensitive; rotate(1, 2, 3, "xy", 90).

Common situations: User-typed axis names with different case or whitespace ('X', ' x '); localization or alternative naming ('horizontal', 'z-axis'); config typos.

Related errors

• Axis must be a str
• Input values except axis must either be float or int: {list(
• Expected a_coeffs to have {self.order + 1} elements for {sel
• Expected b_coeffs to have {self.order + 1} elements for {sel
• k must not be negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/99bdc96dd790886d. Report an issue: GitHub.