TheAlgorithms/Python · critical · TypeError

Parameter n must be int or castable to int.

Error message

Parameter n must be int or castable to int.

What it means

Documented TypeError from project_euler/problem_003/sol3.py:solution when int(n) fails (solution('asd')). CAVEAT: the file's validation uses Python 2 syntax 'except TypeError, ValueError:' and therefore raises SyntaxError under Python 3 at import time - the documented TypeError cannot fire until the clause is rewritten as 'except (TypeError, ValueError):'.

Source

Thrown at project_euler/problem_003/sol3.py:48

    ValueError: Parameter n must be greater than or equal to one.
    >>> solution(-17)
    Traceback (most recent call last):
        ...
    ValueError: Parameter n must be greater than or equal to one.
    >>> solution([])
    Traceback (most recent call last):
        ...
    TypeError: Parameter n must be int or castable to int.
    >>> solution("asd")
    Traceback (most recent call last):
        ...
    TypeError: Parameter n must be int or castable to int.
    """

    try:
        n = int(n)
    except TypeError, ValueError:
        raise TypeError("Parameter n must be int or castable to int.")
    if n <= 0:
        raise ValueError("Parameter n must be greater than or equal to one.")
    i = 2
    ans = 0
    if n == 2:
        return 2
    while n > 2:
        while n % i != 0:
            i += 1
        ans = i
        while n % i == 0:
            n = n // i
        i += 1
    return int(ans)


if __name__ == "__main__":
    print(f"{solution() = }")

View on GitHub (pinned to f5988cc097)

Solutions

1. Parenthesize the exceptions at project_euler/problem_003/sol3.py:48.
2. Pass int or int-castable values afterwards.
3. Guard calls with a small is_valid_n helper shared across the problem_003 variants.
4. Add compile checks for legacy modules to CI.

Example fix

# before
except TypeError, ValueError:
    raise TypeError('Parameter n must be int or castable to int.')

# after
except (TypeError, ValueError):
    raise TypeError('Parameter n must be int or castable to int.') from None

if not is_int_castable(n):
    raise TypeError(f'n must be int-castable, got {n!r}')
solution(n)

def is_int_castable(v) -> bool:
    try:
        int(v)
        return True
    except (TypeError, ValueError):
        return False

try:
    solution(n)
except TypeError:
    ...

When it happens

Trigger: After the syntax fix: solution('asd'), solution(None), solution(3.5) is fine (casts), solution(object()) raises. Today: running or importing the module under Python 3 produces SyntaxError('multiple exception types must be parenthesized').

Common situations: Whole-repo doctest sweeps under Python 3; migration of an old algorithms checkout; harnesses that call every problem_003 solution variant with the same inputs, where sol1/sol2/sol3 all share the same broken guard.

Related errors

• Parameter n must be int or castable to int.
• Parameter n must be int or castable to int.
• Parameter n must be int or castable to int.
• Parameter n must be greater than or equal to one.
• Parameter n must be greater than or equal to one.

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/e81f5115a71431e2. Report an issue: GitHub.