def findMinAndMax(L):

    if L == []:

        return (None, None)

    else:

        min=L[-1]

        max=L[-1]

        for n in L:

            if min-n>0:

                min = n

            elif max-n<0:

                max = n

        return (min,max)

# 测试

if findMinAndMax([]) != (None, None):

    print('测试失败1!')

elif findMinAndMax([7]) != (7, 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!')