import email, email.feedparser, email.parser, timeit


def parsestr(self, text, headersonly = False):
    feed_parser = email.feedparser.FeedParser(self._class)
    
    if headersonly:
        feed_parser._set_headersonly()
    
    feed_parser.feed(text)
    return feed_parser.close()


size = 10 * 2**20
timer = timeit.Timer(lambda: email.message_from_string('-' * size))

print 'Original:', timer.timeit(1)

email.parser.Parser.parsestr = parsestr
print 'Modified:', timer.timeit(1)