ValueError: Client secrets must be for a web or installed app

Question

I am running the quickstart.py example code under Python Quickstart and I am getting the following error:

ValueError: Client secrets must be for a web or installed app.

I created a credentials.json file with project owner rights.

The error occurs in the following piece of code:

if os.path.exists('token.pickle'):
    with open('token.pickle', 'rb') as token:
        creds = pickle.load(token)
# If there are no (valid) credentials available, let the user log in.
if not creds or not creds.valid:
    if creds and creds.expired and creds.refresh_token:
        creds.refresh(Request())
    else:
        flow = InstalledAppFlow.from_client_secrets_file('credentials.json', SCOPES)
        creds = flow.run_local_server()
    # Save the credentials for the next run
    with open('token.pickle', 'wb') as token:
        pickle.dump(creds, token)

I notice also that the token.pickle file is not being created. This is the error output:

  File "updateSlidev01.py", line 51, in <module>
    main()
  File "updateSlidev01.py", line 31, in main
    flow = InstalledAppFlow.from_client_secrets_file('credentials.json', SCOPES)
  File "/Library/Python/2.7/site-packages/google_auth_oauthlib/flow.py", line 174, in from_client_secrets_file
    return cls.from_client_config(client_config, scopes=scopes, **kwargs)
  File "/Library/Python/2.7/site-packages/google_auth_oauthlib/flow.py", line 147, in from_client_config
    'Client secrets must be for a web or installed app.')
ValueError: Client secrets must be for a web or installed app.

Answer 1

The problem was that I was using the json generated under Service account keys Manage service accounts and not the one under OAuth 2.0 client IDs.

Follow this instructor for creating oauth client id. https://developers.google.com/workspace/guides/create-credentials#oauth-client-id

Answer 2

For anyone coming here because they would like to actually connect to the GCP calendar API via a service-account and not this Oauth2 client id, create the creds object in the original example as follows:

from google.oauth2 import service_account

SCOPES = ['https://www.googleapis.com/auth/calendar.readonly']
SERVICE_ACCOUNT_FILE = '/path/to/service.json'

credentials = service_account.Credentials.from_service_account_file(
        SERVICE_ACCOUNT_FILE, scopes=SCOPES)

Assuming the service-account is configured with the correct access, this will access the calendar without prompting user for confirmation.