TheAlgorithms/Python · error · TypeError

Input value of [number={number}] must be an integer

Error message

Input value of [number={number}] must be an integer

What it means

Raised by hexagonal(number) in maths/special_numbers/hexagonal_number.py when the argument is not an int. It computes the n-th hexagonal number with the closed formula n*(2n-1); because isinstance(number, int) is strict, floats (even integral ones like 11.0), strings, and None all fail. Note that bool passes since bool subclasses int.

Source

Thrown at maths/special_numbers/hexagonal_number.py:40

    231
    >>> hexagonal(22)
    946
    >>> hexagonal(0)
    Traceback (most recent call last):
        ...
    ValueError: Input must be a positive integer
    >>> hexagonal(-1)
    Traceback (most recent call last):
        ...
    ValueError: Input must be a positive integer
    >>> hexagonal(11.0)
    Traceback (most recent call last):
        ...
    TypeError: Input value of [number=11.0] must be an integer
    """
    if not isinstance(number, int):
        msg = f"Input value of [number={number}] must be an integer"
        raise TypeError(msg)
    if number < 1:
        raise ValueError("Input must be a positive integer")
    return number * (2 * number - 1)


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Convert integral floats before calling: hexagonal(int(x)) when float(x).is_integer()
2. Fix upstream data types (e.g. use dtype int columns or json int parsing) so the value is a builtin int
3. Add your own isinstance check at the API boundary with a clearer domain-specific message

Example fix

// before
h = hexagonal(11.0)  # TypeError

// after
n = int(11.0)
h = hexagonal(n)

if not isinstance(n, int) or isinstance(n, bool):
    n = int(n)  # only after confirming integrality
h = hexagonal(n)

def is_builtin_int(v) -> TypeGuard[int]:
    return isinstance(v, int) and not isinstance(v, bool)

try:
    h = hexagonal(n)
except TypeError:
    n = int(n)
    h = hexagonal(n)

When it happens

Trigger: Calling hexagonal(11.0), hexagonal('5'), or hexagonal(None). Floats are rejected even when they hold an exact integer value; use of numpy integer types may also fail depending on version.

Common situations: Data arriving from JSON or pandas as floats (11.0 instead of 11), or from a division result; mixing numpy int64 scalars into a codebase that expects builtin ints.

Related errors

• Input value of [number={number}] must be an integer
• Input value of [number={number}] must be an integer
• Input value of [{number=}] must be an integer
• Input value of [number={number}] must be an integer
• Useful years must be an integer

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/fbbcb74e7918d6d0. Report an issue: GitHub.