get unsubscribe method from raw email

get-unsubscribe.py

import sys
import re
import urllib.parse


def get_unsubscribe_methods(eml_path):
	unsubscribe = None
	with open(eml_path, encoding='ascii', errors='ignore') as f:
		for line in f:
			if not line.strip():
				break
			if unsubscribe:
				if line.startswith(' ') or line.startswith('\t'):
					unsubscribe += line.strip()
				else:
					break
			if line.lower().startswith('list-unsubscribe: '):
				unsubscribe = line[18:].strip()
	if not unsubscribe:
		return {}
	methods = {'http': [], 'mail': []}
	for method in re.findall(r"<([^>]+)>", unsubscribe):
		url = urllib.parse.urlparse(method)
		if url.scheme in ['http', 'https']:
			methods['http'].append(method)
		elif url.scheme in ['mailto']:
			methods['mail'].append(method)
	for key in list(methods.keys()):
		if not methods[key]:
			del methods[key]
	return methods


for filename in sys.argv[1:]:
	print(f'----- {filename} -----')
	methods = get_unsubscribe_methods(filename)
	if 'http' in methods:
		print(methods['http'][0])
	elif 'mail' in methods:
		print(methods['mail'][0])
	else:
		print('no available unsubscribe method')