fileinput模块对文本进行全局替换

#!/usr/bin/env python
# -*- coding:UTF-8 -*-
import fileinput
File = 'user.txt'
for line in fileinput.input(File, inplace=1):   # inplace=1，表示做完替换后立刻回到文件初始行
    line = line.replace('003', '002')
    print line,