RFC822 regular expression

import re

# Taken from http://tfletcher.com/lib/rfc822.py
qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]'
dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]'
atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+'
quoted_pair = '\\x5c[\\x00-\\x7f]'
domain_literal = "[\\x5b](?:%s|%s)*[\\x5d]" % (dtext, quoted_pair)
quoted_string = "\\x22(?:%s|%s)*\\x22" % (qtext, quoted_pair)
domain_ref = atom
sub_domain = "(?:%s|%s)" % (domain_ref, domain_literal)
word = "(?:%s|%s)" % (atom, quoted_string)
domain = "%s(?:\\x2e%s)*" % (sub_domain, sub_domain)
local_part = "%s(?:\\x2e%s)*" % (word, word)

# Adding maximum length restrictions
addr_spec = "(?=^.{1,256}$)(?=.{1,64}@)%s\\x40%s" % (local_part, domain)

email_address = re.compile('^%s$' % addr_spec)

if __name__ == '__main__':
    list_of_good = ['somewhere@over.the.rainbow',
                    'SOMEWHERE@over.the.rainbow',
                    'SOMEWHERE@OVER.THE.RAINBOW',
                    'foo@example.com',
                    'paul@io',
                    'foo@bar.example.com',
                    'foo+bar@example.com',
                    'foo.bar@example.com',
                    'foo.bar@[127.0.0.1]',
                    'foo_bar@example.com',
                    'foo-bar@example.com',
                    'cal+henderson@iamcalx.com',
                    '"cal henderson"@iamcalx.com',
                    'cal@[hello world].com',
                    '"foo.bar.@.foo.com"@example.com',
                    ('foo.bar'*9) + '@example.com']

    list_of_bad = ['somewhere.over.the.rainbow',
                   'foo..bar@example.com',
                   '.foo@example.com',
                   'bar.@example.com',
                   'foo bar@example.com',
                   'bar@example com',
                   'bar@another example.com',
                   'foo@bar@test@example.com',
                   # Local part can't exceed 64 chars
                   ('foo.bar'*10) + '@example.com',
                   # Total can't exceed 256
                   'foo.bar.foo.bar.foo.bar.bar@' + ('example'*40)]

    for t in list_of_good:
        assert email_address.match(t)

    for t in list_of_bad:
        assert email_address.match(t) is None