How to create Google API OAuth Credentials object from alternate source

Question

I am working with this simple Google API example:

import httplib2

from apiclient.discovery import build
from oauth2client.client import flow_from_clientsecrets
from oauth2client.file import Storage
from oauth2client.tools import run

# Path to the client_secret.json file downloaded from the Developer Console
CLIENT_SECRET_FILE = 'client_secret.json'

# Check https://developers.google.com/gmail/api/auth/scopes for all available scopes
OAUTH_SCOPE = 'https://www.googleapis.com/auth/gmail.readonly'

# Location of the credentials storage file
STORAGE = Storage('gmail.storage')

# Start the OAuth flow to retrieve credentials
flow = flow_from_clientsecrets(CLIENT_SECRET_FILE, scope=OAUTH_SCOPE)
http = httplib2.Http()

# Try to retrieve credentials from storage or run the flow to generate them
credentials = STORAGE.get()
if credentials is None or credentials.invalid:
  credentials = run(flow, STORAGE, http=http)

# Authorize the httplib2.Http object with our credentials
http = credentials.authorize(http)

# Build the Gmail service from discovery
gmail_service = build('gmail', 'v1', http=http)

And seeing as I have already gone through the OAuth flow previously (in a different non-Python app) and have my refresh tokens, etc. I would like to skip the first portion of this example and either manually create the expected storage file gmail.storage or create the credentials object some other way.

The problem is I can't find any documentation about the expected format of this storage file, or what should be in it, or how to instantiate the credentials object in any other way. Sorry that I cannot show any work here, but I'm at a loss. Any point in the right direction would be greatly appreciated.

Solution 1

Very simple, apparently this works:

from oauth2client.client import GoogleCredentials
from oauth2client import GOOGLE_TOKEN_URI

access_token = None
token_expiry = None
token_uri = GOOGLE_TOKEN_URI
user_agent = 'Python client library'
revoke_uri = None

gCreds = GoogleCredentials( 
    access_token, 
    client_id,
    client_secret, 
    refresh_token, 
    token_expiry,
    token_uri, 
    user_agent,
    revoke_uri=revoke_uri
    )

Solution 2

As explained here: in Google Cloud Platform's github

you can also use a string to setup this. Specially a json string

import json
import os
from google.oauth2 import service_account
from google.cloud import translate


info = json.loads(os.environ['GOOGLE_APPLICATION_CREDENTIALS_JSON_STRING'])
creds = service_account.Credentials.from_service_account_info(info)
# Instantiates a client
translate_client = translate.Client(credentials=creds)

Please note that I used Google Translate's API for this example but it's the same logic.

There is a bit more explanation in this git issue too: https://github.com/GoogleCloudPlatform/google-cloud-python/issues/4477