python对txt文本的截取和写入

txt文本截取

1. 有个test.txt文件的内容是这样的，总共三行：

123b456'789?A
123b456'789?A
123b456'789?A

• 怎么截取固定标识前的一段字符呢？

——例如我只要b左边的123

• 用readlines和find

#!/usr/bin python3
# -*- coding: utf-8 -*-

def txt_clip(file_path: str, tag: str):
    with open(file_path, 'r', encoding="utf8") as f:
        all_data = f.readlines()
        for i in all_data:
            print(i[:i.find(tag)])


if __name__ == '__main__':
    txt_clip(file_path="./test.txt", tag="b")

2. 怎么保存处理的结果呢？

• 逐行写入到一个新的txt文件new_test.txt

#!/usr/bin python3
# -*- coding: utf-8 -*-

def txt_clip_and_save_as_a_file(file_path: str, new_file_path: str, tag: str):
    with open(file_path, 'r', encoding="utf8") as f:
        all_data = f.readlines()
        with open(new_file_path, 'w') as new_f:
            for i in all_data:
                new_f.write(i[:i.find(tag)] + '\n')


if __name__ == '__main__':
    txt_clip_and_save_as_a_file(file_path="./test.txt", new_file_path="./new_test.txt", tag="b")

• 新文件的内容就是这样：

123
123
123