At the beginning of my contact with Openstack development, I always thought that some functions of Openstack could only be called using Restful API. This is easy to do. I used to write Python and often deal with Rest, but after reading this article from IBM, I found that there are still more suitable ones. Method calls are like calling Python third-party modules to develop Openstack automation scripts.
Please refer to this article for details:
https://www.ibm.com/developerworks/cn/cloud/library/cl-openstack-pythonapis/#resources
Python API: OpenStack's Hidden Secrets
But whether it is more effective than Rest or whether Rest is comprehensive depends on future practice.