display_email.py

#!/usr/bin/env python3
# Foundations of Python Network Programming, Third Edition
# https://github.com/brandon-rhodes/fopnp/blob/m/py3/chapter12/display_email.py
#
# Someday this script will use message.iter_attachments() instead of
# walking through them itself, but http://bugs.python.org/issue21079

import argparse, email.policy, sys

def main(binary_file):
    policy = email.policy.SMTP
    message = email.message_from_binary_file(binary_file, policy=policy)
    for header in ['From', 'To', 'Date', 'Subject']:
        print(header + ':', message.get(header, '(none)'))
    print()

    try:
        body = message.get_body(preferencelist=('plain', 'html'))
    except KeyError:
        print('<This message lacks a printable text or HTML body>')
    else:
        print(body.get_content())

    for part in message.walk():
        cd = part['Content-Disposition']
        is_attachment = cd and cd.split(';')[0].lower() == 'attachment'
        if not is_attachment:
            continue
        content = part.get_content()
        print('* {} attachment named {!r}: {} object of length {}'.format(
            part.get_content_type(), part.get_filename(),
            type(content).__name__, len(content)))

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Parse and print an email')
    parser.add_argument('filename', nargs='?', help='File containing an email')
    args = parser.parse_args()
    if args.filename is None:
        main(sys.stdin.buffer)
    else:
        with open(args.filename, 'rb') as f:
            main(f)