txt_匹配并拆分出需要字符串

环境：
s1_str.txt中每行一个字符串
```
未找到：zhangsan 不在ldap中
hahaha
未找到：lisi 不在ldap中
```
需求：
匹配到`未找到：zhangsan 不在ldap中`这种字符串，拆分出姓名并保存到 d1_str.txt 文件中。

```python
# -*- coding: utf-8 -*-

import re

#with open('s2_str.txt', "r", encoding='gb2312') as sf:  # 中文用gb2312编码打开
with open('s1_str.txt', "r", encoding='gb2312') as sf:
    with open('d1_str.txt', 'a', encoding='utf-8') as df:
        for line in sf.readlines():
            try:
                #print(line)
                line_str = line.strip('\n')
                ## 判断一个字符串是否包含合法IP地址
                #ip = re.search(r'((25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)', ip)

# 判断一个字符串是否包含待匹配的字符串
                #line_user = re.search(r'(?<=BJ\\).*?(?=:)', line_str)

# 判断一个字符串是否包含待匹配的字符串
                print(line_str, type(line_str))
                line_user = re.search(r'(?<=未找到：).*?(?= 不在ldap中)', line_str)

print("正则匹配结果：", line_user)
                if line_user:
                    line_user = line_user.group()  # 提取出字符串
                    mywr = line_user
                    #mywr = line_str + mywr  # 带原字符串
                    df.write(mywr)
                    df.write('\n')
                else:
                    pass
                    #line_user = ""

# except:
            except Exception as e:
                print("*错误" * 88)
                print(e)
                print(line)

print("正常结束")
        df.write("正常结束")
        df.write('\n')
```