I don't see a method in a Python client which checks if the given set is empty.
As documentation says from the command line I can use:
asinfo -h <host> -v 'sets/<namespace>/<set>'
but it is for a single host only.
Another way is to look at the output of:
asadm -h <host> -e 'info set'
How would you implement such a method in Python?
Use the "info" API in the client: https://www.aerospike.com/apidocs/python/client.html#aerospike.Client.info_all
client.info_all("sets/<namespace>/<set>")
Then sum the stat you are interested.