TheAlgorithms/Python · error · ValueError

Input value must be a positive integer

Error message

Input value must be a positive integer

What it means

Raised by check_args() in physics/horizontal_projectile_motion.py when init_velocity is not an int or float. check_args is the shared validator called by horizontal_distance and related projectile functions; it enforces numeric types before any trigonometry runs. bool passes isinstance(x, (int, float)) since bool subclasses int, and strings, None, and Decimal all fail.

Source

Thrown at bit_manipulation/binary_count_setbits.py:32

    >>> binary_count_setbits(4294967295)
    32
    >>> binary_count_setbits(0)
    0
    >>> binary_count_setbits(-10)
    Traceback (most recent call last):
        ...
    ValueError: Input value must be a positive integer
    >>> binary_count_setbits(0.8)
    Traceback (most recent call last):
        ...
    TypeError: Input value must be a 'int' type
    >>> binary_count_setbits("0")
    Traceback (most recent call last):
        ...
    TypeError: '<' not supported between instances of 'str' and 'int'
    """
    if a < 0:
        raise ValueError("Input value must be a positive integer")
    elif isinstance(a, float):
        raise TypeError("Input value must be a 'int' type")
    return bin(a).count("1")


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Convert to float before calling: float(velocity_str).
2. Check for None / missing optional values and supply a default or skip.
3. Catch TypeError at input boundaries to re-prompt or reject the form field.

Example fix

# before
dist = horizontal_distance(input('v: '), 45)  # str -> TypeError

# after
dist = horizontal_distance(float(input('v: ')), 45)

if not isinstance(init_velocity, (int, float)) or isinstance(init_velocity, bool):
    init_velocity = float(init_velocity)  # or raise
dist = horizontal_distance(init_velocity, angle)

def is_numeric_velocity(v: object) -> bool:
    return isinstance(v, (int, float)) and not isinstance(v, bool)

try:
    dist = horizontal_distance(v, angle)
except TypeError as e:
    if "velocity" in str(e):
        dist = horizontal_distance(float(v), angle)
    else:
        raise

When it happens

Trigger: horizontal_distance('50', 45) with a string velocity from input() or a web form; passing None when an optional velocity was not provided; passing a numpy float64 is fine (it subclasses float), but a Decimal or Fraction is not.

Common situations: Unconverted user input from CLI prompts or HTML forms; data loaded as strings from JSON/CSV where numbers were quoted; Optional[float] fields that are None flowing into the call.

Related errors

• Input value must be a 'int' type
• Expected a list of numbers as input, found {type(item).__nam
• Expected a list of numbers as input, found {type(point).__na
• Input must be an integer
• Initial orbit radius must be greater than zero.

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/c0584909fb695d35. Report an issue: GitHub.