def findMinAndMax(L):

    if L==[]:

        return(None,None)

    else:

        mi,ma =L[0],L[0]

        for i in L:

            if i>=ma:

                ma = i

            if i<=mi:

                mi = i

    return(mi,ma)

# 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!')