def findMinAndMax(L):
    if L ==[]:
        return (None,None)
    max = L[0];
    min = L[0];
    for x in L:
        if x>=max:
            max = x
        if x<=min:
            min = x
    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!')