I made a Line Bot that uses Python to retrieve unread Gmail emails!

Purpose

Get mail from Gmail with Line Bot and send unread messages to the sender and subject to Line.

Development environment

• Flask==1.1.1
• line-bot-sdk==1.14.0
• oauth2client==4.1.3
• httplib2==0.14.0
• google-api-python-client==1.7.11
• google-auth==1.6.3
• google-auth-httplib2==0.0.3
• google-auth-oauthlib==0.4.1

reference

Check Gmail emails with Python --I used it as a reference to enable Google's API. Get mail from Gmail API using Python --I referred to how to use the Gmail API.

Source code

main.py

from flask import Flask, request, abort
 
from linebot import (
    LineBotApi, WebhookHandler
)
from linebot.exceptions import (
    InvalidSignatureError
)
from linebot.models import (
    MessageEvent, TextMessage, TextSendMessage, LocationMessage, VideoMessage,
    FollowEvent, UnfollowEvent, PostbackEvent, TemplateSendMessage,
    ButtonsTemplate, CarouselTemplate, CarouselColumn, PostbackTemplateAction
)
from linebot.exceptions import LineBotApiError

import os
import json
import sys
import re

import Gmail 
 
app = Flask(__name__)

YOUR_CHANNEL_ACCESS_TOKEN = os.environ["YOUR_CHANNEL_ACCESS_TOKEN"]
YOUR_CHANNEL_SECRET = os.environ["YOUR_CHANNEL_SECRET"]

line_bot_api = LineBotApi(YOUR_CHANNEL_ACCESS_TOKEN)
handler = WebhookHandler(YOUR_CHANNEL_SECRET)

@app.route("/callback", methods=['POST'])
def callback():
    signature = request.headers['X-Line-Signature']
 
    body = request.get_data(as_text=True)
    app.logger.info("Request body: " + body)
 
    try:
        handler.handle(body, signature)
    except InvalidSignatureError:
        abort(400)

    return 'OK'

@handler.add(MessageEvent, message=TextMessage)
def handle_message(event):
    text = event.message.text
    user_id = event.source.user_id
    if 'Email' in text:
      mail = Gmail.GmailAPI()
      # get the reply message
      messages = mail.process_message()
      # reply
      line_bot_api.reply_message(
            event.reply_token,
            TextSendMessage(text=str(messages))
        )

if __name__ == "__main__":
    port = int(os.getenv("PORT", 5000))
    app.run(host="0.0.0.0", port=port)

When the bot receives a message containing the string "mail", it gets an unread message from Gmail and replies.

Gmail.py

from googleapiclient.discovery import build
from httplib2 import Http
from oauth2client import file, client, tools

class GmailAPI:
    def __init__(self):
        # If modifying these scopes, delete the file token.json.
        self._SCOPES = 'https://www.googleapis.com/auth/gmail.readonly'

    def ConnectGmail(self):
        store = file.Storage('token.json')
        creds = store.get()
        if not creds or creds.invalid:
            flow = client.flow_from_clientsecrets('credentials.json', self._SCOPES)
            creds = tools.run_flow(flow, store)
        service = build('gmail', 'v1', http=creds.authorize(Http()))

        return service

    def GetMessageList(self):

        # connect to API
        service = self.ConnectGmail()

        MessageList = []

        query = 'is:unread'

        # get all the messages (maximum=20)
        messageIDlist = service.users().messages().list(userId='me',maxResults=20,q=query).execute()

        # if no messages, stop return error
        if messageIDlist['resultSizeEstimate'] == 0: 
            return 'error'
        # Get information about the mails
        for message in messageIDlist['messages']:
            row = {}
            MessageDetail = service.users().messages().get(userId='me',id=message['id']).execute()
            for header in MessageDetail['payload']['headers']:
                # get the senders of the messages
                if header['name'] == 'From':
                    row['from'] = header['value']
                # get the subject of the messages
                elif header['name'] == 'Subject':
                    row['subject'] = header['value']
            MessageList.append(row)
        return MessageList

    def process_message(self):
        messagelist = self.GetMessageList()
        # If there is no messages new, reply 'No message'
        if messagelist == 'error':
            reply = 'No message'
            return reply 

        # make reply message
        reply = ''
        for mlist in messagelist:
            from_name = mlist['from'].split('<')[0] + ':'
            sub = '「' + mlist['subject'] + '」'
            message = '{}\n{}'.format(from_name, sub)
            reply += message 
            reply += '\n\n'
        return reply

Using Gmail API, GetMessageList gets the sender and subject of unread mail, and process_message converts them to the character string when replying and returns it.

result

I have erased the sender's name, but I got the name and title and was able to reply!

About the future

I would like to implement the following two in the future.

• Use the push function to automatically retrieve and send unread emails.
• Instead of typing "mail", set up a button so that you can get unread mail with that button.