Extract eml Files from mails

import re
import email
import hashlib
from os import walk

# dir to save extracted files
outdir = '/path/to/folder'

# path to folder containing mailmessages
sourcedir = '/home/myuser/.Maildir/.INBOX.Ham/cur'

f = []
r = re.compile("^[0-9]+.*$")

for (dirpath, dirnames, filenames) in walk(sourcedir):
        f.extend(filter(r.match, filenames))
for file in f:
    file = sourcedir + '/' + file
        hash = hashlib.sha256(file).hexdigest()
        with open(file) as fl:
                msg = email.message_from_file(fl)
        for part in msg.walk():
                if part.get_content_type() == "application/octet-stream":
                        with open(outdir + '/' + hash + '.eml', 'w') as fl:
                                fl.write(part.get_payload(decode=True).replace('\r', "\r\n"))