TheAlgorithms/Python · error · ValueError

Input value of [{number=}] must be > 0

Error message

Input value of [{number=}] must be > 0

What it means

Raised by is_proth_number(number) when the argument is a builtin int but <= 0. The algorithm subtracts 1 and repeatedly divides by 2, which is undefined for inputs < 1 (and 1 is special-cased to return False just below this guard), so non-positive integers are rejected.

Source

Thrown at maths/special_numbers/proth_number.py:93

    True
    >>> is_proth_number(34)
    False
    >>> is_proth_number(-1)
    Traceback (most recent call last):
        ...
    ValueError: Input value of [number=-1] must be > 0
    >>> is_proth_number(6.0)
    Traceback (most recent call last):
        ...
    TypeError: Input value of [number=6.0] must be an integer
    """
    if not isinstance(number, int):
        message = f"Input value of [{number=}] must be an integer"
        raise TypeError(message)

    if number <= 0:
        message = f"Input value of [{number=}] must be > 0"
        raise ValueError(message)

    if number == 1:
        return False

    number -= 1
    n = 0
    while number % 2 == 0:
        n += 1
        number //= 2
    return number < 2**n


if __name__ == "__main__":
    import doctest

    doctest.testmod()

    for number in range(11):

View on GitHub (pinned to f5988cc097)

Solutions

1. Filter candidates to >= 1 before calling (or >= 2, since 1 returns False anyway)
2. Validate user-supplied candidates at your boundary
3. Treat non-positive inputs as 'not a Proth number' in your own wrapper before delegating

Example fix

// before
ok = is_proth_number(-1)  # ValueError

// after
ok = is_proth_number(25)

if n < 1:
    ok = False  # non-positives are simply not Proth numbers
else:
    ok = is_proth_number(n)

When it happens

Trigger: Calling is_proth_number(0) or is_proth_number(-1). This fires only after the isinstance check passes; non-integers raise the TypeError above.

Common situations: Screening raw user input or sensor values that can be 0/negative without pre-filtering; iterating a range that includes 0.

Related errors

• Input value of [number={number}] must be > 0
• 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

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/a1d0c757883938b4. Report an issue: GitHub.