python3 to download certain unread email's attatchment

[python] get_unread_email_and_download_attachments

 import email
    import imaplib
    import os
    from email.header import decode_header

    detach_dir = '.'
    if 'attachments' not in os.listdir(detach_dir):
        os.mkdir('attachments')

    import os
    already_fielnames = os.listdir("attachments")

    userName = 'xxxx@??.yyy'
    passwd = 'password'

    try:
        imapSession = imaplib.IMAP4('imap.qq.com')
        typ, accountDetails = imapSession.login(userName, passwd)
        if typ != 'OK':
            print('Not able to sign in!')
            raise

        imapSession.select('inbox')
        typ, data = imapSession.search(None, '(UNSEEN)')
        if typ != 'OK':
            print('Error searching Inbox.')
            raise

        ids = data[0].split()
        ids.reverse()
        for msgId in ids:
            from email.parser import HeaderParser
            data = imapSession.fetch(msgId, '(BODY[HEADER.FIELDS (SUBJECT FROM)])')
            header_data = data[1][0][1]
            header_data = email.message_from_bytes(header_data)
            header_data = dict(header_data._headers)

            fileName, _ = decode_header(header_data.get('Subject', ''))[0]
            if isinstance(fileName, bytes):
                fileName = fileName.decode()
            header_data['Subject'] = fileName

            if 'xxxx' not in header_data['From'] or 'xxxx' not in header_data['Subject']:
                break

            typ, messageParts = imapSession.fetch(msgId, '(RFC822)')
            if typ != 'OK':
                raise

            emailBody = messageParts[0][1]
            mail = email.message_from_bytes(emailBody)
            for part in mail.walk():
                if part.get_content_maintype() == 'multipart':
                    continue
                if part.get('Content-Disposition') is None:
                    continue

                fileName = part.get_filename()

                fileName, _ = decode_header(fileName)[0]
                if isinstance(fileName, bytes):
                    fileName = fileName.decode()

                if fileName in already_fielnames:
                    break

                if bool(fileName):
                    filePath = os.path.join(detach_dir, 'attachments', fileName)
                    if not os.path.isfile(filePath):
                        fp = open(filePath, 'wb')
                        fp.write(part.get_payload(decode=True))
                        fp.close()
        imapSession.close()
        imapSession.logout()
    except Exception as e:
        raise