Accessing backend APIs from Python clients

If you want to access an Cloud Endpoints API from a Python client, you need to use the Google APIs Python Client Library. If the API doesn't require any authentication, your client can access the API as shown in the following example code:

import pprint

from googleapiclient.discovery import build


def main():
  # Build a service object for interacting with the API.
  api_root = 'https://guestbook.appspot.com/_ah/api'
  api = 'guestbook'
  version = 'v0.2'
  discovery_url = '%s/discovery/v1/apis/%s/%s/rest' % (api_root, api, version)
  service = build(api, version, discoveryServiceUrl=discovery_url)

  # Fetch all greetings and print them out.
  response = service.greetings().list().execute()
  pprint.pprint(response)

  # Fetch a single greeting and print it out.
  response = service.greetings().get(id='9001').execute()
  pprint.pprint(response)


if __name__ == '__main__':
  main()

In the example code:

  • api_root is the frontend root URL under which your API methods are exposed. Usually, the URL is https://YOUR_PROJECT_ID.appspot.com/_ah/apicode> where YOUR_PROJECT_ID represents your Google Cloud Platform (GCP)
  • api is the name of the API.
  • version is the version of the backend API.

Accessing an API requiring Authentication

If the backend API requires authentication, you need use both the Google APIs Python Client Library and the OAuth2.0 Client Library.

Your client can get the required authorization and access the API by using code similar to the following:

import argparse
import pprint
import sys

from googleapiclient import discovery
import httplib2
import oauth2client
from oauth2client import tools


CLIENT_ID = 'YOUR_CLIENT_ID'
CLIENT_SECRET = 'YOUR_CLIENT_SECRET'
SCOPE = 'https://www.googleapis.com/auth/userinfo.email'
USER_AGENT = 'my-cmdline-tool/1.0'
OAUTH_DISPLAY_NAME = 'My Commandline Tool'


def main(argv):
  # Parse command line flags used by the oauth2client library.
  parser = argparse.ArgumentParser(
      description='Auth sample',
      formatter_class=argparse.RawDescriptionHelpFormatter,
      parents=[tools.argparser])
  flags = parser.parse_args(argv[1:])

  # Acquire and store oauth token.
  storage = oauth2client.file.Storage('guestbook.dat')
  credentials = storage.get()

  if credentials is None or credentials.invalid:
    flow = oauth2client.client.OAuth2WebServerFlow(
        client_id=YOUR_CLIENT_ID,
        client_secret=YOUR_CLIENT_SECRET,
        scope=SCOPE,
        user_agent=USER_AGENT,
        oauth_displayname=OAUTH_DISPLAY_NAME)
    credentials = tools.run_flow(flow, storage, flags)
  http = httplib2.Http()
  http = credentials.authorize(http)

  # Build a service object for interacting with the API.
  api_root = 'https://guestbook.appspot.com/_ah/api'
  api = 'guestbook'
  version = 'v0.2'
  discovery_url = '%s/discovery/v1/apis/%s/%s/rest' % (api_root, api, version)
  service = discovery.build(
      api, version, discoveryServiceUrl=discovery_url, http=http)

  # Fetch all greetings and print them out.
  response = service.greetings().list().execute()
  pprint.pprint(response)

  # Fetch a single greeting and print it out.
  response = service.greetings().get(id='9001').execute()
  pprint.pprint(response)


if __name__ == '__main__':
  main(sys.argv)

Notice that SCOPE must be set as shown. For information about YOUR_CLIENT_ID and YOUR_CLIENT_SECRET, see Creating client IDs.

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