用python写函数，用户传入修改的文件名，与要修改的内容，执行函数，完成整个文件的批量修改操作

import os
def alter_file(filename,old_value,new_value):
    with open(filename,encoding="utf-8") as f, open("%s.bak"%filename,"w",encoding="utf-8") as f2:
        # f.write("尹石榴，男\n")
        # f.write("尹艺霏,女\t")
        # new_value = "小"
        # old_value = "尹"
        for line in f:
            if old_value in line:
                line = line.replace(old_value,new_value)
                f2.write(line)#写入
                print("把%s替换成%s"%(old_value,new_value))
            else:
                print("这个%s不在文件中"%old_value)