pip freeze > requirements.txt
pip download -r requirements.txt -d packages
https://blog.csdn.net/qq_45152711/article/details/139071022?utm_medium=distribute.pc_relevant.none-task-blog-2~default~baidujs_baidulandingword~default-0-139071022-blog-132881635.235^v43^control&spm=1001.2101.3001.4242.1&utm_relevant_index=3
