from collections import Iterable

def findMinAndMax(l):

if l == []:
    return (None,None)
max = l[0]
min = l[0]        
for v in l:
    if max < v:
        max = v
print('max is:',max)
for v in l:
    if v < min:
        min = v
print('min is :',min)
return (min,max)

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!')