sample.py

#!/usr/bin/python

import httplib2

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

import base64
import email
from apiclient import errors

from email.mime.text import MIMEText


def GetMimeMessage(service, user_id, msg_id):
  """Get a Message and use it to create a MIME Message.

  Args:
    service: Authorized Gmail API service instance.
    user_id: User's email address. The special value "me"
    can be used to indicate the authenticated user.
    msg_id: The ID of the Message required.

  Returns:
    A MIME Message, consisting of data from Message.
  """
  try:
    message = service.users().messages().get(userId=user_id, id=msg_id,
                                             format='raw').execute()

    print 'Message snippet: %s' % message['snippet']

    msg_str = base64.urlsafe_b64decode(message['raw'].encode('ASCII'))

    mime_msg = email.message_from_string(msg_str)

    return mime_msg
  except errors.HttpError, error:
    print 'An error occurred: %s' % error

def CreateMessage(sender, to, subject, message_text):
  """Create a message for an email.

  Args:
    sender: Email address of the sender.
    to: Email address of the receiver.
    subject: The subject of the email message.
    message_text: The text of the email message.

  Returns:
    An object containing a base64url encoded email object.
  """
  message = MIMEText(message_text)
  message['to'] = to
  message['from'] = sender
  message['subject'] = subject
  return {'raw': base64.urlsafe_b64encode(message.as_string())}

def SendMessage(service, user_id, message):
  """Send an email message.

  Args:
    service: Authorized Gmail API service instance.
    user_id: User's email address. The special value "me"
    can be used to indicate the authenticated user.
    message: Message to be sent.

  Returns:
    Sent Message.
  """
  try:
    message = (service.users().messages().send(userId=user_id, body=message)
               .execute())
    print 'Message Id: %s' % message['id']
    return message
  except errors.HttpError, error:
    print 'An error occurred: %s' % error

# Path to the client_secret.json file downloaded from the Developer Console
CLIENT_SECRET_FILE = 'client_secret.json'

# Check https://developers.google.com/gmail/api/auth/scopes for all available scopes
OAUTH_SCOPE = 'https://www.googleapis.com/auth/gmail.compose'

# Location of the credentials storage file
STORAGE = Storage('gmail.storage')

# Start the OAuth flow to retrieve credentials
flow = flow_from_clientsecrets(CLIENT_SECRET_FILE, scope=OAUTH_SCOPE)
http = httplib2.Http()

# Try to retrieve credentials from storage or run the flow to generate them
credentials = STORAGE.get()
if credentials is None or credentials.invalid:
  credentials = run(flow, STORAGE, http=http)

# Authorize the httplib2.Http object with our credentials
http = credentials.authorize(http)

# Build the Gmail service from discovery
gmail_service = build('gmail', 'v1', http=http)

# Retrieve a page of threads
#messages = gmail_service.users().messages().list(userId='me').execute()
#
#for message in messages['messages']:
#    msg_id = message['id']
#    print GetMimeMessage(gmail_service, 'me', msg_id)
#    break

message = CreateMessage(sender='louiedinh+daily@gmail.com', to='louiedinh@gmail.com', subject='testing', message_text="hi!")

SendMessage(gmail_service, 'me', message)