python 代码片断,查找列表中某个数字的前后数字

#coding=utf-8
list=[282435671,2000,9000035401,1,9000035701,2,252444730,3000,9000035601,2,9000035401,1,9000035701,2]
mid=input("shu ru mu biao shu zi:")

try:
	index=list.index(mid)
	if index==0:
		print None
		print list[index+1]
	elif index==len(list)-1:
		print list[index-1]
		print None
	else:
		print list[index-1]
		print list[index+1]

except ValueError:
	print None
	print None

import os
os.system("pause")