def findMinAndMax(L):
    if len(L) == 0:
        return (None, None)
    else:
        min = max = L[0]
        for l in L[1:]:
            if l > max:
                max = l
            if l < min:
                min = l
    return (min, max)


# 测试if findMinAndMax([]) != (None, None):
    print('测试失败1!')
elif findMinAndMax([7]) != (7, 7):
    print(findMinAndMax([7])
    print('测试失败2!')
elif findMinAndMax([7, 1]) != (1, 7):
    print('测试失败3!')
elif findMinAndMax([7, 1, 3, 9, 5]) != (1, 9):
    print('测试失败4!')
else:
    print('测试成功!')