python创建virtualenv虚拟环境
pip install virtualenv
virtualenv env_py36_crawl
env_py36_crawl\Scripts\activate
deactivate
pip freeze > req.txt
pip install -r req.txt
pip install virtualenv
virtualenv env_py36_crawl
env_py36_crawl\Scripts\activate
deactivate
pip freeze > req.txt
pip install -r req.txt