编写Yaml文件：属性错误

我正在尝试读取yaml文件，替换其中的一部分并将结果写入相同的文件，但是出现属性错误。

码

import yaml
import glob
import re
from yaml import load, dump
from yaml import CLoader as Loader, CDumper as Dumper
import io

list_paths = glob.glob("my_path/*.yaml")

for path in list_paths:    
    with open(path, 'r') as stream:
        try:
            text = load(stream, Loader=Loader)
            text = str(text)
            print text
            if "my_string" in text:
                start = "'my_string': '"
                end = "'"
                m = re.compile(r'%s.*?%s' % (start,end),re.S)
                m = m.search(text).group(0)
                text[m] = "'my_string': 'this is my string'"  
        except yaml.YAMLError as exc:
            print(exc)
    with io.open(path, 'w', encoding = 'utf8') as outfile:
        yaml.dump(text, path, default_flow_style=False, allow_unicode=True)

错误我得到该yaml_dump行的错误

AttributeError: 'str' object has no attribute 'write' 

到目前为止我尝试过的

• 没有将文本转换为字符串，但随后m.search在行上出现错误：

  TypeError：预期的字符串或缓冲区

• 首先转换为字符串，然后dict再次转换为，但是我从代码中得到此错误text: dict(text)：ValueError: dictionary update sequence element #0 has length 1; 2 is required

Yaml文件

my string: something
string2: something else

预期结果：yaml文件

my string: this is my string
string2: something else