TheAlgorithms/Python · error · ValueError

iterations must be defined as integers

Error message

iterations must be defined as integers

What it means

Raised by fizz_buzz(iterations, number) when the first parameter is not an int (isinstance(iterations, int) fails). Note bool is a subclass of int, so True/False pass; floats, strings, and None raise. It is the first of three sequential validation checks in the function.

Source

Thrown at dynamic_programming/fizz_buzz.py:38

        ...
    ValueError: starting number must be
                             and integer and be more than 0
    >>> fizz_buzz(10,-5)
    Traceback (most recent call last):
        ...
    ValueError: Iterations must be done more than 0 times to play FizzBuzz
    >>> fizz_buzz(1.5,5)
    Traceback (most recent call last):
        ...
    ValueError: starting number must be
                             and integer and be more than 0
    >>> fizz_buzz(1,5.5)
    Traceback (most recent call last):
        ...
    ValueError: iterations must be defined as integers
    """
    if not isinstance(iterations, int):
        raise ValueError("iterations must be defined as integers")
    if not isinstance(number, int) or not number >= 1:
        raise ValueError(
            """starting number must be
                         and integer and be more than 0"""
        )
    if not iterations >= 1:
        raise ValueError("Iterations must be done more than 0 times to play FizzBuzz")

    out = ""
    while number <= iterations:
        if number % 3 == 0:
            out += "Fizz"
        if number % 5 == 0:
            out += "Buzz"
        if 0 not in (number % 3, number % 5):
            out += str(number)

        # print(out)

View on GitHub (pinned to f5988cc097)

Solutions

1. Convert the argument to int at the boundary: fizz_buzz(int(iterations), number).
2. Use argparse type=int or explicit schema validation for config/CLI input.
3. Check types before calling when data comes from untrusted sources.

Example fix

# before
fizz_buzz(request.args.get('n'), 1)  # str like '15' -> ValueError

# after
fizz_buzz(int(request.args.get('n')), 1)

if not isinstance(iterations, int) or isinstance(iterations, bool):
    iterations = int(iterations)
fizz_buzz(iterations, number)

def is_plain_int(value: object) -> bool:
    return isinstance(value, int) and not isinstance(value, bool)

try:
    out = fizz_buzz(iterations, number)
except ValueError as exc:
    if 'iterations must be defined as integers' in str(exc):
        out = fizz_buzz(int(iterations), number)
    else:
        raise

When it happens

Trigger: fizz_buzz(1, 5.5) as shown in the doctest (iterations=1 is fine, but symmetrically fizz_buzz('10', 1) raises here); passing a float iteration count like fizz_buzz(10.0, 1); passing None or a string parsed from CLI args without conversion.

Common situations: CLI or HTTP query parameters arriving as strings; argparse without type=int; JSON config values that deserialize as floats (10.0 vs 10).

Related errors

• All weights must be integers but got weight of type {type(wt
• numbers must be an iterable of integers
• numbers must be an iterable of integers
• The parameter days should be a list of integers
• 'float' object cannot be interpreted as an integer

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/6566e99ca199c27d. Report an issue: GitHub.