pip install -i https://pypi.doubanio.com/simple/ flask
pip install -i https://pypi.doubanio.com/simple/ -r requirements.txt
豆瓣 https://pypi.doubanio.com/simple/ 网易 https://mirrors.163.com/pypi/simple/ 阿里云 https://mirrors.aliyun.com/pypi/simple/ 腾讯云 https://mirrors.cloud.tencent.com/pypi/simple 清华大学 https://pypi.tuna.tsinghua.edu.cn/simple/