TheAlgorithms/Python · critical · TypeError

Parameter nth must be int or castable to int.

Error message

Parameter nth must be int or castable to int.

What it means

Documented TypeError from project_euler/problem_007/sol2.py:solution when int(nth) fails (solution('asd')). The raise even uses 'from None' (correct py3 style) but the except clause itself is py2 syntax ('except TypeError, ValueError:'), so under Python 3 the module fails to import and this TypeError is unreachable until the clause is fixed.

Source

Thrown at project_euler/problem_007/sol2.py:91

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

    try:
        nth = int(nth)
    except TypeError, ValueError:
        raise TypeError("Parameter nth must be int or castable to int.") from None
    if nth <= 0:
        raise ValueError("Parameter nth must be greater than or equal to one.")
    primes: list[int] = []
    num = 2
    while len(primes) < nth:
        if is_prime(num):
            primes.append(num)
            num += 1
        else:
            num += 1
    return primes[len(primes) - 1]


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

View on GitHub (pinned to f5988cc097)

Solutions

1. Change 'except TypeError, ValueError:' to 'except (TypeError, ValueError):' at project_euler/problem_007/sol2.py:91.
2. Then pass int or int-castable nth (e.g. 10001).
3. Validate nth with isinstance or isdigit checks in callers.
4. Run ruff/flake8 or py_compile over the module to catch the syntax class of error automatically.

Example fix

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

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

nth = int(nth)
if nth <= 0:
    raise ValueError('nth must be >= 1')
solution(nth)

def is_valid_prime_index(nth) -> bool:
    return isinstance(nth, int) and not isinstance(nth, bool) and nth >= 1

try:
    solution(nth)
except TypeError as e:
    if 'castable' in str(e):
        ...

When it happens

Trigger: After the fix: solution('asd'), solution(None). Today: importing or executing project_euler/problem_007/sol2.py under Python 3 raises SyntaxError('multiple exception types must be parenthesized') at line 91 instead.

Common situations: py3 test sweeps over the repo's euler solutions; unconverted CLI or query-string parameters reaching solution(); mixed py2/py3 idioms in one file (this file also uses modern 'list[int]' annotations, which makes the py2 except clause easy to miss).

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 int or castable to int.
• Parameter n must be int or castable to int.

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/2534c1752de2c40c. Report an issue: GitHub.