Is this a command line tool? If so, try the following which will persist the credentials after prompting you the first time:
import httplib2
from oauth2client.file import Storage
from oauth2client.client import flow_from_clientsecrets
from oauth2client.tools import run
from apiclient.discovery import build
storage = Storage("saved_user_creds.dat")
credentials = storage.get()
if credentials is None or credentials.invalid:
credentials = run(flow_from_clientsecrets("client_secrets2.json", scope=["https://www.googleapis.com/auth/drive"]), storage)
http = credentials.authorize(httplib2.Http())
service = build("drive", "v2", http)
print service.files().list().execute()