Format subject email

I want to recover the value "SUBJECT" of an email

import imaplib
import os
import email

email_user = 'xxxxxxx@xxxxxxx'
email_pass = 'xxxxxxxx'

M = imaplib.IMAP4_SSL('imap.gmail.com', 993)
M.login(email_user, email_pass)
M.select('INBOX')

typ, message_numbers = M.search(None, 'ALL')

num = b'2420'
typ, data = M.fetch(num, '(RFC822)')

raw_email = data[0][1].decode('utf-8')
email_message = email.message_from_string(raw_email)

print(email_message['Subject'])

the value is

=?UTF-8?Q?=5BNAS=5FLEBARS=5D_Active_Backup_for_Business_=2D_La_t=C3=A2che_?=
=?UTF-8?Q?de_sauvegarde_DBS_=2D_SIDEXIS_sur_NAS=5FLEBARS_est_termin=C3=A9e?=

but i want this encode

[NAS_LEBARS] Active Backup for Business - La tâche de sauvegarde DBS - SIDEXIS sur NAS_LEBARS est terminée

Thanks

Solution

This pretty much does what you need, it:

takes each encoded line
extracts the part that needs to be decoded
converts that,
- replacing each '_' with a space
- replacing each '=XX' with the byte with that hex code
- leaving all other characters as is
decodes the entire result as a UTF-8 bytes array

import re

subject = [
    '=?UTF-8?Q?=5BNAS=5FLEBARS=5D_Active_Backup_for_Business_=2D_La_t=C3=A2che_?=',
    '=?UTF-8?Q?de_sauvegarde_DBS_=2D_SIDEXIS_sur_NAS=5FLEBARS_est_termin=C3=A9e?='
]


def convert_content(content):
    iter_content = iter(content)
    try:
        while True:
            ch = next(iter_content)
            if ch == '_':
                yield b' '
            elif ch == '=':
                yield bytearray.fromhex(next(iter_content)+next(iter_content))
            else:
                yield ch.encode('utf-8')
    except StopIteration:
        pass


def process(data):
    for line in data:
        m = re.match(r'=\?(?:utf|UTF)-8\?(?:q|Q)\?(.*)\?=', line)
        yield b''.join(convert_content(m.group(1))).decode('utf-8')


print(''.join(process(subject)))

Output:

[NAS_LEBARS] Active Backup for Business - La tâche de sauvegarde DBS - SIDEXIS sur NAS_LEBARS est terminée