A quick and dirty script to get all the hosts in a vCenter.

hosts_listing.py

#!/usr/bin/env python

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()

host_list = []
stack = [content.rootFolder]
while stack:
    entity = stack.pop()
    if entity.__class__.__name__ == 'vim.HostSystem':
        host_list.append(entity)
    if hasattr(entity, 'host'):
        if isinstance(entity.host, list):
            for host in entity.host:
                host_list.append(host)
        else:
            host_list.append(entity.host)
    if hasattr(entity, 'hostFolder'):
        stack.append(entity.hostFolder)
    if hasattr(entity, 'childEntity'):
        for child in entity.childEntity:
            stack.append(child)


print('Host systems found: ')
for host in host_list:
    print(host.name)