练习，替换txt文档中的信息

import os
with open('b','a+',encoding= 'utf-8') as f,open('b2.bak','w',encoding= 'utf-8') as f2:
    f.seek(0)
    for i in f:
        new_i = i.replace('一','二')
        f2.write(new_i)
os.remove('b')
os.rename('b2.bak','b')