pip installation specifies the source, version, file installation

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple robotframework-appiumlibrary==1.4.1.1
pip install -i https://pypi.doubanio.com/simple/ -r requirements.txt
pip install flask_restful -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com