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/sol1.py:solution when int(n) fails (e.g. solution('asd')). CAVEAT: the guard uses Python 2 syntax 'except TypeError, ValueError:' - under Python 3 this file raises SyntaxError at import, so the TypeError never actually fires until the clause is parenthesized.

Source

Thrown at project_euler/problem_003/sol1.py:84

    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.")
    max_number = 0
    if is_prime(n):
        return n
    while n % 2 == 0:
        n //= 2
    if is_prime(n):
        return n
    for i in range(3, int(math.sqrt(n)) + 1, 2):
        if n % i == 0:
            if is_prime(n // i):
                max_number = n // i
                break
            elif is_prime(i):
                max_number = i
    return max_number

View on GitHub (pinned to f5988cc097)

Solutions

1. Fix the except clause to 'except (TypeError, ValueError):' at project_euler/problem_003/sol1.py:84.
2. Then pass int or int-castable values (e.g. 600851475143, '13195').
3. Pre-check with isinstance(n, int) in caller code.
4. Include this module in doctest CI to catch the SyntaxError class of breakage.

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 isinstance(n, (int, float)) and not str(n).isdigit():
    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([1]). As written today: any import or execution of project_euler/problem_003/sol1.py under Python 3 fails with SyntaxError('multiple exception types must be parenthesized').

Common situations: Running this repo's doctests or test suite under Python 3; CI pipelines that import every solution module; migrating an old checkout of the algorithms repository to modern Python.

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/8fe7e94277ac22f9. Report an issue: GitHub.