sending_mail.py

import base64
import pickle
from email.mime.text import MIMEText
from googleapiclient.discovery import build


def create_message(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_bytes()).decode()}


def send_message(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.
    """
    message = (service.users().messages().send(userId=user_id, body=message)
               .execute())
    print('Message Id: %s' % message['id'])
    return message


def get_service(path):
    with open(rf'{path}', 'rb') as token:
        creds = pickle.load(token)
    service = build('gmail', 'v1', credentials=creds)
    return service


path_to_pickle = r"PATH_TO_PICKLE"
subject = "Hi! from python"
sender = "YOUR_MAIL_ID"
to = "MAIL_ID_TO_WHOM_YOU_WANT_TO_SEND"
message_text = "This e-mail is sent from Gmail API via python! Isn't that Cool?"

user_id = "me"

service = get_service(path_to_pickle)
raw_text = create_message(sender, to, subject, message_text)
message_data = send_message(service, user_id, raw_text)

@ysaito8015 Thanks, for the edits.