"""统计工具 —— dim4 Q4.2 自检产物。"""

from __future__ import annotations


def mean(values: list[float]) -> float:
    if not values:
        return 0.0
    return sum(values) / len(values)


def median(values: list[float]) -> float:
    if not values:
        return 0.0
    s = sorted(values)
    n = len(s)
    mid = n // 2
    if n % 2:
        return s[mid]
    return (s[mid - 1] + s[mid]) / 2


if __name__ == "__main__":
    assert mean([]) == 0.0
    assert mean([1, 2, 3]) == 2.0
    print("M-OK")
    assert median([]) == 0.0
    assert median([1, 3]) == 2.0
    assert median([1, 2, 3, 4]) == 2.5
    print("MD-OK")
    print("all stats self-tests passed")