Use property collector to retrieve names quickly

gistfile1.txt

#!/usr/bin/env python
"""
Written by Nathan Prziborowski
Github: https://github.com/prziborowski
This code is released under the terms of the Apache 2
http://www.apache.org/licenses/LICENSE-2.0.html
The property collector can be used to fetch a subset of properties
for a large amount of objects with fewer round trips that iterating.
This sample shows how to use the TraversalSpec to get properties
of another object without multiple calls.
"""
import sys
from pyVmomi import vim, vmodl
from pyVim.connect import SmartConnectNoSSL, Disconnect
from pyVim.task import WaitForTask
from tools import cli

__author__ = 'prziborowski'


def setup_args():
    parser = cli.build_arg_parser()
    return cli.prompt_for_password(parser.parse_args())


def get_obj(si, root, vim_type):
    container = si.content.viewManager.CreateContainerView(root, vim_type,
                                                           True)
    view = container.view
    container.Destroy()
    return view


def get_filter_spec(containerView, objType, path):
    traverse_spec = vmodl.query.PropertyCollector.TraversalSpec()
    traverse_spec.name = 'traverse'
    traverse_spec.path = 'view'
    traverse_spec.skip = False
    traverse_spec.type = vim.view.ContainerView

    obj_spec = vmodl.query.PropertyCollector.ObjectSpec()
    obj_spec.obj = containerView
    obj_spec.skip = True
    obj_spec.selectSet.append(traverse_spec)

    prop_spec = vmodl.query.PropertyCollector.PropertySpec()
    prop_spec.type = objType
    prop_spec.pathSet = path

    return vmodl.query.PropertyCollector.FilterSpec(propSet=[prop_spec],
                                                    objectSet=[obj_spec])

def process_result(result, objects):
    for o in result.objects:
        if o.obj not in objects:
            objects[o.obj] = {}
        for p in o.propSet:
            objects[o.obj][p.name] = p.val

def collect_properties(si, root, vim_type, props):
    objects = {}
    # Start with all the VMs from container, which is easier to write than
    # PropertyCollector to retrieve them.
    view_mgr = si.content.viewManager
    container = view_mgr.CreateContainerView(root,
                                             [vim_type], True)
    try:
        filter_spec = get_filter_spec(container, vim_type, props)
        options = vmodl.query.PropertyCollector.RetrieveOptions()
        pc = si.content.propertyCollector
        result = pc.RetrievePropertiesEx([filter_spec], options)
        process_result(result, objects)
        while result.token is not None:
            result = pc.ContinueRetrievePropertiesEx(result.token)
            process_result(result, objects)
    finally:
        container.Destroy()
    return objects


def main():
    args = setup_args()
    si = SmartConnectNoSSL(host=args.host,
                           user=args.user,
                           pwd=args.password,
                           port=args.port)
    vms = collect_properties(si, si.content.rootFolder, vim.VirtualMachine,
                             ['config', 'name', 'guest', 'parent', 'runtime'])
    hosts = collect_properties(si, si.content.rootFolder, vim.HostSystem,
                               ['name'])
    print("VMs: %d" % len(vms))
    print("Hosts: %d" % len(hosts))

# Start program
if __name__ == "__main__":
    main()

You can use retrievePropertiesEx to fetch config.name for all vms and this is pretty fast.