Read gmail through API with python. See https://github.com/abhishekchhibber/Gmail-Api-through-Python/blob/master/gmail_read.py

gmail.py

#!/usr/bin/env python

#from __future__ import print_function
import pickle
import os.path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request

import json
import base64

import dateutil.parser as parser
from bs4 import BeautifulSoup

# If modifying these scopes, delete the file token.pickle.
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.pickle 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.pickle'):
        with open('token.pickle', 'rb') as token:
            creds = pickle.load(token)
    # 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.pickle', 'wb') as token:
            pickle.dump(creds, token)

    service = build('gmail', 'v1', credentials=creds)

    # Call the Gmail API
    results = service.users().labels().list(userId='me').execute()
    labels = results.get('labels', [])
    mails = service.users().messages().list(userId='me').execute()

    for m in mails["messages"]:
        message = service.users().messages().get(userId="me", id=m["id"]).execute() # fetch the message using API
        payld = message['payload'] # get payload of the message 
        headr = payld['headers'] # get header of the payload

        temp_dict = {}
        for one in headr: # getting the Subject
            if one['name'] == 'Subject':
                msg_subject = one['value']
                temp_dict['Subject'] = msg_subject
            else:
                pass


        for two in headr: # getting the date
            if two['name'] == 'Date':
                msg_date = two['value']
                date_parse = (parser.parse(msg_date))
                m_date = (date_parse.date())
                temp_dict['Date'] = str(m_date)
            else:
                pass

        for three in headr: # getting the Sender
            if three['name'] == 'From':
                msg_from = three['value']
                temp_dict['Sender'] = msg_from
            else:
                pass


        # Fetching message body
        if "data" in payld["body"]:
            data = payld['body']['data'] # fetching the message parts
            data = data.replace("-","+")
            data = data.replace("_","/")
            clean = base64.b64decode(data) # decoding from Base64 to UTF-8
            soup = BeautifulSoup(clean, "lxml" )
            #mssg_body = soup.body()
            # mssg_body is a readible form of message body
            # depending on the end user's requirements, it can be further cleaned 
            # using regex, beautiful soup, or any other method
            #temp_dict['Message_body'] = mssg_body

            print(soup.body())

if __name__ == '__main__':
    main()