Python quickstart

Create a Python command-line application that makes requests to the Gmail API.

Quickstarts explain how to set up and run an app that calls a Google Workspace API. This quickstart uses a simplified authentication approach that is appropriate for a testing environment. For a production environment, we recommend learning about authentication and authorization before choosing the access credentials that are appropriate for your app.

This quickstart uses Google Workspace's recommended API client libraries to handle some details of the authentication and authorization flow.

Objectives

  • Set up your environment.
  • Install the client library.
  • Set up the sample.
  • Run the sample.

Prerequisites

To run this quickstart, you need the following prerequisites:

  • A Google account with Gmail enabled.

Set up your environment

To complete this quickstart, set up your environment.

Enable the API

Before using Google APIs, you need to turn them on in a Google Cloud project. You can turn on one or more APIs in a single Google Cloud project.

If you're using a new Google Cloud project to complete this quickstart, configure the OAuth consent screen. If you've already completed this step for your Cloud project, skip to the next section.

  1. In the Google Cloud console, go to Menu > Google Auth platform > Branding.

    Go to Branding

  2. If you have already configured the Google Auth platform, you can configure the following OAuth Consent Screen settings in Branding, Audience, and Data Access. If you see a message that says Google Auth platform not configured yet, click Get Started:
    1. Under App Information, in App name, enter a name for the app.
    2. In User support email, choose a support email address where users can contact you if they have questions about their consent.
    3. Click Next.
    4. Under Audience, select Internal.
    5. Click Next.
    6. Under Contact Information, enter an Email address where you can be notified about any changes to your project.
    7. Click Next.
    8. Under Finish, review the Google API Services User Data Policy and if you agree, select I agree to the Google API Services: User Data Policy.
    9. Click Continue.
    10. Click Create.
  3. For now, you can skip adding scopes. In the future, when you create an app for use outside of your Google Workspace organization, you must change the User type to External. Then add the authorization scopes that your app requires. To learn more, see the full Configure OAuth consent guide.

Authorize credentials for a desktop application

To authenticate end users and access user data in your app, you need to create one or more OAuth 2.0 Client IDs. A client ID is used to identify a single app to Google's OAuth servers. If your app runs on multiple platforms, you must create a separate client ID for each platform.
  1. In the Google Cloud console, go to Menu > Google Auth platform > Clients.

    Go to Clients

  2. Click Create Client.
  3. Click Application type > Desktop app.
  4. In the Name field, type a name for the credential. This name is only shown in the Google Cloud console.
  5. Click Create.

    The newly created credential appears under "OAuth 2.0 Client IDs."

  6. Save the downloaded JSON file as credentials.json, and move the file to your working directory.

Install the Google client library

  • Install the Google client library for Python:

    pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib

Configure the sample

  1. In your working directory, create a file named quickstart.py.

  2. Include the following code in quickstart.py:

    gmail/quickstart/quickstart.py
    import os.path

from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError

# If modifying these scopes, delete the file token.json.
SCOPES = ["https://www.googleapis.com/auth/gmail.readonly"]


def main():
  """Shows basic usage of the Gmail API.
  Lists the user's Gmail labels.
  """
  creds = None
  # The file token.json stores the user's access and refresh tokens, and is
  # created automatically when the authorization flow completes for the first
  # time.
  if os.path.exists("token.json"):
    creds = Credentials.from_authorized_user_file("token.json", SCOPES)
  # 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(port=0)
    # Save the credentials for the next run
    with open("token.json", "w") as token:
      token.write(creds.to_json())

  try:
    # Call the Gmail API
    service = build("gmail", "v1", credentials=creds)
    results = service.users().labels().list(userId="me").execute()
    labels = results.get("labels", [])

    if not labels:
      print("No labels found.")
      return
    print("Labels:")
    for label in labels:
      print(label["name"])

  except HttpError as error:
    # TODO(developer) - Handle errors from gmail API.
    print(f"An error occurred: {error}")


if __name__ == "__main__":
  main()

Run the sample

  1. In your working directory, build and run the sample:

    python3 quickstart.py
  1. The first time you run the sample, it prompts you to authorize access:
    1. If you're not already signed in to your Google Account, sign in when prompted. If you're signed in to multiple accounts, select one account to use for authorization.
    2. Click Accept.

    Your Python application runs and calls the Gmail API.

    Authorization information is stored in the file system, so the next time you run the sample code, you aren't prompted for authorization.

Next steps