def findMinAndMax(L):
    #返回值中格式为(Min , Max)    
    if L == []:
        return (None, None)
    else:
        min = L[0]
        max = L[0]
        for i in L:
            if min > i:
                min=i
            if max < i:
                max=i
    return (min,max)

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