def findMinAndMax(L):    if L == []: #判断L是否为空集        return (None,None)    Max = L[0]    Min = L[0]    for i in L:        if i > Max: #找到最大值            Max = i    for i in L:        if i < Min:  #找到最小值            Min = i    return (Min,Max)# 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!')