Using Google Calendar API v 3 with Python

Question

Can someone please give me a clear explanation of how to get the Google Calendar API v3 working with the Python Client? Specifically, the initial OAuth stage is greatly confusing me. All I need to do is access my own calendar, read it, and make changes to it. Google provides this code for configuring my app:

import gflags
import httplib2

from apiclient.discovery import build
from oauth2client.file import Storage
from oauth2client.client import OAuth2WebServerFlow
from oauth2client.tools import run

FLAGS = gflags.FLAGS

# Set up a Flow object to be used if we need to authenticate. This
# sample uses OAuth 2.0, and we set up the OAuth2WebServerFlow with
# the information it needs to authenticate. Note that it is called
# the Web Server Flow, but it can also handle the flow for native
# applications
# The client_id and client_secret are copied from the API Access tab on
# the Google APIs Console
FLOW = OAuth2WebServerFlow(
    client_id='YOUR_CLIENT_ID',
    client_secret='YOUR_CLIENT_SECRET',
    scope='https://www.googleapis.com/auth/calendar',
    user_agent='YOUR_APPLICATION_NAME/YOUR_APPLICATION_VERSION')

# To disable the local server feature, uncomment the following line:
# FLAGS.auth_local_webserver = False

# If the Credentials don't exist or are invalid, run through the native client
# flow. The Storage object will ensure that if successful the good
# Credentials will get written back to a file.
storage = Storage('calendar.dat')
credentials = storage.get()
if credentials is None or credentials.invalid == True:
  credentials = run(FLOW, storage)

# Create an httplib2.Http object to handle our HTTP requests and authorize it
# with our good Credentials.
http = httplib2.Http()
http = credentials.authorize(http)

# Build a service object for interacting with the API. Visit
# the Google APIs Console
# to get a developerKey for your own application.
service = build(serviceName='calendar', version='v3', http=http,
       developerKey='YOUR_DEVELOPER_KEY')

But (a) it makes absolutely no sense to me; the comment explanations are terrible, and (b) I don't know what to put in the variables. I've registered my program with Google and signed up for a Service Account key. But all that gave me was an encrypted key file to download, and a client ID. I have no idea what a "developerKey" is, or what a "client_secret" is? Is that the key? If it is, how do I get it, since it is actually contained in an encrypted file? Finally, given the relatively simple goals of my API use (i.e., it's not a multi-user, multi-access operation), is there a simpler way to be doing this? Thanks.

Answer 1

A simple (read: way I've done it) way to do this is to create a web application instead of a service account. This may sound weird since you don't need any sort of web application, but I use this in the same way you do - make some queries to my own calendar/add events/etc. - all from the command line and without any sort of web-app interaction. There are ways to do it with a service account (I'll tinker around if you do in fact want to go on that route), but this has worked for me thus far.

After you create a web application, you will then have all of the information indicated above (side note: the sample code above is based on a web application - to use a service account your FLOW needs to call flow_from_clientsecrets and further adjustments need to be made - see here). Therefore you will be able to fill out this section:

FLOW = OAuth2WebServerFlow(
    client_id='YOUR_CLIENT_ID',
    client_secret='YOUR_CLIENT_SECRET',
    scope='https://www.googleapis.com/auth/calendar',
    user_agent='YOUR_APPLICATION_NAME/YOUR_APPLICATION_VERSION')

You can now fill out with the values you see in the API console (client_id = the entire Client ID string, client_secret = the client secret, scope is the same and the user_agent can be whatever you want). As for the service line, developerKey is the API key you can find under the Simple API Access section in the API console (label is API key):

service = build(serviceName='calendar', version='v3', http=http, 
    developerKey='<your_API_key>')

You can then add in a simple check like the following to see if it worked:

events = service.events().list(calendarId='<your_email_here>').execute()
print events

Now when you run this, a browser window will pop up that will allow you to complete the authentication flow. What this means is that all authentication will be handled by Google, and the authentication response info will be stored in calendar.dat. That file (which will be stored in the same directory as your script) will contain the authentication info that the service will now use. That is what is going here:

storage = Storage('calendar.dat')
credentials = storage.get()
if credentials is None or credentials.invalid == True:
  credentials = run(FLOW, storage)

It checks for the existence of valid credentials by looking for that file and verifying the contents (this is all abstracted away from you to make it easier to implement). After you authenticate, the if statement will evaluate False and you will be able to access your data without needing to authenticate again.

Hopefully that shines a bit more light on the process - long story short, make a web application and use the parameters from that, authenticate once and then forget about it. I'm sure there are various points I'm overlooking, but hopefully it will work for your situation.