def findMinAndMax(L):
    minNum = None
    maxNum = None
    if len(L) > 0:
        minNum = L[0]
        maxNum = L[0]

    for n in L:
        if minNum > n:
            minNum = n
        if maxNum < n:
            maxNum = n
    return minNum, maxNum


# 测试
if findMinAndMax([]) != (None, None):
    print('测试失败!')
elif findMinAndMax([7]) != (7, 7):
    print('测试失败!')
elif findMinAndMax([7, 1]) != (1, 7):
    print('测试失败!')
elif findMinAndMax([7, 1, 3, 9, 5]) != (1, 9):
    print('测试失败!')
else:
    print('测试成功!')

`