$$添加换行符

从博客园导出md格式，让typora去打开，遇到其中公式标识符的前后换行没有了，用vscode去渲染没事，为了能够正常渲染，用python给前后添加换行符。

import os
import re

def process_md_file(file_path):
    with open(file_path, 'r', encoding='utf-8') as file:
        md_text = file.read()
        processed_text = re.sub(r'\$\$', '\n$$\n', md_text)

    # 写入处理后的MD文本到原文件
    with open(file_path, 'w', encoding='utf-8') as file:
        file.write(processed_text)

def batch_process_md_files(directory):
    # 遍历目录下的所有文件
    for root, dirs, files in os.walk(directory):
        for file in files:
            if file.endswith('.md'):
                file_path = os.path.join(root, file)
                process_md_file(file_path)
                print(f"Processed file: {file_path}")

# 指定要处理的目录为当前工作目录
directory = os.getcwd()

# 批量处理Markdown文件
batch_process_md_files(directory)