datacenters_listing.py

from __future__ import print_function

from pyVim import connect
from pyVmomi import vim

si = connect.SmartConnect(host='vcsa',  user='my_user', pwd='my_password')
content = si.RetrieveContent()

# A list comprehension of all the root folder's first tier children...
datacenters = [entity for entity in content.rootFolder.childEntity
                          if hasattr(entity, 'vmFolder')]

# Just to prove to ourselves we have that list:
for dc in datacenters:
    print(dc.name)