Google API: getting Credentials from refresh token with oauth2client.client

Question

I am using googles official oauth2client.client to access the google plus api. I have a refresh token (that does not expire) stored in a database, and need to recreate the temporary "Credentials" (access token) from that.

But I could not find a way to do this with to official library supplied by google.

So I hacked around it: used urllib to access the API that gives me a new access_token from the refresh_token. Using the access_token I can then use the library.

I must be missing somthing!

from apiclient import discovery
from oauth2client.client import AccessTokenCredentials
from urllib import urlencode
from urllib2 import Request , urlopen, HTTPError
import json

# ==========================================

def access_token_from_refresh_token(client_id, client_secret, refresh_token):
  request = Request('https://accounts.google.com/o/oauth2/token',
    data=urlencode({
      'grant_type':    'refresh_token',
      'client_id':     client_id,
      'client_secret': client_secret,
      'refresh_token': refresh_token
    }),
    headers={
      'Content-Type': 'application/x-www-form-urlencoded',
      'Accept': 'application/json'
    }
  )
  response = json.load(urlopen(request))
  return response['access_token']

# ==========================================

access_token = access_token_from_refresh_token(CLIENT_ID, CLIENT_SECRET, REFRESH_TOKEN)

# now I can use the library properly
credentials = AccessTokenCredentials(access_token, "MyAgent/1.0", None)
http = credentials.authorize(httplib2.Http())
service = discovery.build('plus', 'v1', http=http)
google_request = service.people().get(userId='me')
result = google_request.execute(http=http)

Answer 1

I use: oauth2client.client.GoogleCredentials

    cred = oauth2client.client.GoogleCredentials(access_token,client_id,client_secret,
                                          refresh_token,expires_at,"https://accounts.google.com/o/oauth2/token",some_user_agent)
    http = cred.authorize(httplib2.Http())
    cred.refresh(http)
    self.gmail_service = discovery.build('gmail', 'v1', credentials=cred)