用python在文件中指定位置插入内容

with open("d:/bbb/test.txt","rt") as f:
    content=str(f.readlines())
    tab=re.search('\"',content)
    pos=tab.start()
    print(pos)

    insert=input("输入要插入的内容：")
    with open("d:/bbb/test.txt","wt") as f:
        content=content[:pos+1]+insert+content[pos+1:]
        f.writelines(content)
with open("d:/bbb/test.txt","rt") as f:
    print(f.read())