Backups all GMail emails+attachments from a given label AND from a given sender.

backup_gmail.py

import argparse
import imaplib
import email
import os

parser = argparse.ArgumentParser(description = 'Backup GMail mailbox. Turn on less secure apps before running https://www.google.com/settings/security/lesssecureapps')
parser.add_argument('--username', required = True)
parser.add_argument('--password', required = True)
parser.add_argument('-o', default = '.')
parser.add_argument('--label', default = 'INBOX')
parser.add_argument('--to')
parser.add_argument('--content', action = 'store_true')
parser.add_argument('--addresses', action = 'store_true')
args = parser.parse_args()

gmail = imaplib.IMAP4_SSL('imap.gmail.com', 993)
gmail.login(args.username, args.password)
gmail.select(args.label)
search = gmail.search(None, '(TO "{}")'.format(args.to) if args.to else '')

for email_id in search[1][0].split():
    resp, data = gmail.fetch(email_id, '(RFC822)')
    mail = email.message_from_string(data[0][1])
    email_dir = os.path.join(args.o, email_id)

    if args.addresses:
        print(mail['From'], mail['To'], mail.keys())

    if args.content:
        if not os.path.exists(email_dir):
            os.makedirs(email_dir)
        with open(os.path.join(email_dir, 'email.txt'), 'w') as f:
            f.write(str(mail).decode("quoted-printable"))
        if mail.get_content_maintype() != 'multipart':
            continue
        for part in mail.walk():
            if part.get_content_maintype() == 'multipart':
                continue
            if part.get('Content-Disposition') is None:
                continue
                continue

            filename = part.get_filename()
            counter = 1
            if not filename:
                filename = 'part-{:03d}{}'.format(counter, 'bin')
                counter += 1

            attachment_path = os.path.join(email_dir, filename)
            if not os.path.isfile(attachment_path):
                with open(attachment_path, 'wb') as f:
                    f.write(part.get_payload(decode = True))