List users with Google Directory API

gistfile1.txt

#!/usr/bin/python

from apiclient.discovery import build
import httplib2
from oauth2client.service_account import ServiceAccountCredentials
from oauth2client.client import GoogleCredentials
import logging
import json
import sys

from apiclient import discovery
from apiclient import errors
import oauth2client
from oauth2client import client
from oauth2client import tools
from oauth2client.client import flow_from_clientsecrets

scope = 'https://www.googleapis.com/auth/admin.directory.user'

# A. with service accounts
#credentials = ServiceAccountCredentials.from_p12_keyfile('adminapi@fabled-ray-104117.iam.gserviceaccount.com',
#                                                           'project1-5fc7d442817b.p12',
#                                                           scopes=scope)  
#credentials = credentials.create_delegated('admin@demoapp2.com')


# B. with client_secrets and login as domain admin
flow  = flow_from_clientsecrets('client_secret.json',
                               scope=scope,
                               redirect_uri='urn:ietf:wg:oauth:2.0:oob')
auth_uri = flow.step1_get_authorize_url()
print 'goto the following url ' +  auth_uri
code = raw_input('Enter token:')
credentials = flow.step2_exchange(code)

http = httplib2.Http()
http = credentials.authorize(http)

data = ''
service = discovery.build('admin', 'directory_v1', http=http)
page_token = None
while True:
    try:
      results = service.users().list(customer='C023zw3ee', domain='demoapp2.com', pageToken=page_token).execute()
      users = results.get('users', [])
      print json.dumps(users, sort_keys=True, indent=4)
      for u in users:
         print json.dumps(u['primaryEmail'], sort_keys=True, indent=4)
      page_token = results.get('nextPageToken')
      if not page_token:
        break    
    except errors.HttpError, error:
      print 'An error occurred: %s' % error
      break    

Is a domain and customer field are required parameters in all the scenarios of directory API??

you can use either https://developers.google.com/admin-sdk/directory/reference/rest/v1/users/list

Either the customer or the domain parameter must be provided.