TheAlgorithms/Python · error · ValueError

n must be >= 0

Error message

n must be >= 0

What it means

Raised by compute_nums() in project_euler/problem_046/sol1.py when n <= 0. The check 'if n <= 0' rejects both zero and negatives, but the message says 'n must be >= 0', so the message is misleading: passing 0 also raises even though 0 satisfies the stated constraint. Effectively the function requires n >= 1.

Source

Thrown at project_euler/problem_046/sol1.py:92

    [5777, 5993]
    >>> compute_nums(0)
    Traceback (most recent call last):
        ...
    ValueError: n must be >= 0
    >>> compute_nums("a")
    Traceback (most recent call last):
        ...
    ValueError: n must be an integer
    >>> compute_nums(1.1)
    Traceback (most recent call last):
        ...
    ValueError: n must be an integer

    """
    if not isinstance(n, int):
        raise ValueError("n must be an integer")
    if n <= 0:
        raise ValueError("n must be >= 0")

    list_nums = []
    for num in range(len(odd_composites)):
        i = 0
        while 2 * i * i <= odd_composites[num]:
            rem = odd_composites[num] - 2 * i * i
            if is_prime(rem):
                break
            i += 1
        else:
            list_nums.append(odd_composites[num])
            if len(list_nums) == n:
                return list_nums

    return []


def solution() -> int:

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass n >= 1, since 0 is actually rejected by the guard.
2. Short-circuit zero counts before calling: if n == 0: return [] (or equivalent) instead of calling compute_nums.
3. If you must handle 0, wrap the call: result = [] if n == 0 else compute_nums(n).
4. Upstream, treat the message as a doc bug and code against the real contract n >= 1.

Example fix

# before
n = len(matches)  # can be 0
nums = compute_nums(n)  # ValueError: n must be >= 0

# after
nums = compute_nums(n) if n > 0 else []

if n < 1:
    if n == 0:
        result = []  # zero-count short circuit
    else:
        raise ValueError(f"n must be >= 1, got {n}")
else:
    result = compute_nums(n)

def is_valid_count(n) -> bool:
    return isinstance(n, int) and n >= 1  # real contract, despite message

try:
    nums = compute_nums(n)
except ValueError as e:
    if str(e) == "n must be >= 0":
        nums = []  # treat zero/negative request as empty result
    else:
        raise

When it happens

Trigger: compute_nums(0) (raises despite the message implying 0 is allowed), compute_nums(-3). Any caller that clamps or defaults a count to 0 (e.g. max(0, len(results))) will trip this.

Common situations: Empty-input handling where a caller legitimately computes a count of 0 (empty list) and forwards it; default parameter values of 0; iterating ranges that start at 0.

Related errors

• Parameter nth must be greater than or equal to one.
• Hand should contain only 5 cards: {hand!r}
• gon_side must be in the range [3, 5]
• a gon ring should have a length that is a multiple of 3
• Please enter an integer greater than 0

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/f23503a164a27d0d. Report an issue: GitHub.