Sending e-mails using gmail API

A simple python 3 program that is using gmail API for sending e-mails.
By Kostas Koutsogiannopoulos

Introduction

This article is a part of a future post regarding asyncronous tasks runing inside a django web application.

We decided to publish it separately because our research for sending e-mail using google's API, led us only to python 2 snippets that doesn't work with python 3.

You can find google's guide for gmail API call with python here: https://developers.google.com/gmail/api/quickstart/python

...and for sending mail sample python code here:

In this article we will accomplish the same result using python 3.

Starting with the basics

Create a new python 3 virtual environment:

username@hostname:~$ virtualenv gmailApp -p python3
Running virtualenv with interpreter /usr/bin/python3 Using base prefix '/usr' New python executable in /home/username/gmailApp/bin/python3 Also creating executable in /home/username/gmailApp/bin/python Installing setuptools, pip, wheel...done.

Activate the environment and check python version:

username@hostname:~$ source gmailApp/bin/activate
(gmailApp) username@hostname:~$ python --version
Python 3.4.3

Install the Google Client Library with all the dependencies:

(gmailApp) username@hostname:~$ pip install --upgrade google-api-python-client

As the message announces, the packages are installed:

Successfully installed google-api-python-client-1.5.1 httplib2-0.9.2 oauth2client-2.2.0 pyasn1-0.1.9 pyasn1-modules-0.0.8 rsa-3.4.2 simplejson-3.8.2 six-1.10.0 uritemplate-0.6

Create a project on Google

Follow this link with a browser:

Click "Continue" to enable API and create project:

Click "Go to credentials":

Select options like the screen above and click "What credentials do I need?":

Give a Product name.

Optionaly click "More customization options" and give more information about your application.

Click Continue:

Click "Download" and save the json file as "gmail_test_secret.json".

Python 3 snippet

In the same directory with the secret json file, create the python program gmailTest.py:

gmailTest.py

import httplib2
import os

from apiclient import discovery, errors
import oauth2client
from oauth2client import client
from oauth2client import tools

import base64
from email.mime.text import MIMEText

SCOPES = 'https://www.googleapis.com/auth/gmail.compose'
CLIENT_SECRET_FILE = 'gmail_test_secret.json'
APPLICATION_NAME = 'Gmail API Python Test'

try:
    import argparse
    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()
except ImportError:
    flags = None

def SendMessage(service, user_id, message): # Send an email message.
    try:
      message = (service.users().messages().send(userId=user_id, body=message)
               .execute())
      print ('Message Id: %s' % message['id'])
      return message
    except errors.HttpError as error:
      print ('An error occurred: %s' % error)

def get_credentials(): # Gets valid user credentials from disk.
    credential_dir = '/home/username/gmailApp'
    if not os.path.exists(credential_dir):
        os.makedirs(credential_dir)
    credential_path = os.path.join(credential_dir,
                                   'gmail-python-test.json')

    store = oauth2client.file.Storage(credential_path)
    credentials = store.get()
    if not credentials or credentials.invalid:
        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)
        flow.user_agent = APPLICATION_NAME
        if flags:
            credentials = tools.run_flow(flow, store, flags)
        else: # Needed only for compatibility with Python 2.6
            credentials = tools.run(flow, store)
        print('Storing credentials to ' + credential_path)
    return credentials

def create_message(sender, to, subject, message_text): # Create a message for an email.
    message = MIMEText(message_text)
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject
    raw = base64.urlsafe_b64encode(bytes(str(message), "utf-8"))
    return {'raw': raw.decode()}

def main( sender, recepient, subject, text_body ):
    credentials = get_credentials()
    http = credentials.authorize(httplib2.Http())
    service = discovery.build('gmail', 'v1', http=http)
    testMessage = create_message( sender, recepient, subject, text_body )
    SendMessage( service, sender, testMessage )

if __name__ == '__main__':
    main( 'username@gmail.com', 'username@mycompany.com', 'Test mail subject', 'Test mail body' )