shade is a simple client library for operating OpenStack clouds. The key word here is simple. Clouds can do many many many things - but there are probably only about 10 of them that most people care about with any regularity. If you want to do complicated things, you should probably use the lower level client libraries - or even the REST API directly. However, if what you want is to be able to write an application that talks to clouds no matter what crazy choices the deployer has made in an attempt to be more hipster than their self-entitled narcissist peers, then shade is for you.
shade started its life as some code inside of ansible. ansible has a bunch of different OpenStack related modules, and there was a ton of duplicated code. Eventually, between refactoring that duplication into an internal library, and adding logic and features that the OpenStack Infra team had developed to run client applications at scale, it turned out that we'd written nine-tenths of what we'd need to have a standalone library.
Sometimes an example is nice.
from shade import * import time # Initialize cloud # Cloud configs are read with os-client-config cloud = openstack_cloud('mordred') # OpenStackCloud object has an interface exposing OpenStack services methods print cloud.list_servers() s = cloud.list_servers() # But you can also access the underlying python-*client objects cinder = cloud.cinder_client volumes = cinder.volumes.list() volume_id = [v for v in volumes if v.status == 'available'].id nova = cloud.nova_client print nova.volumes.create_server_volume(s.id, volume_id, None) attachments =  print volume_id while not attachments: print "Waiting for attach to finish" time.sleep(1) attachments = cinder.volumes.get(volume_id).attachments print attachments