def findMinAndMax(L):
    if L==[]:
        return None,None
    if len(L)==1:
        return L[0],L[0]
    min=max=L[0]
    for n in L[1:]:
        if max<n:
           max=n
        elif min>n:
           min=n
    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!')