new tree

   soup_login = BeautifulSoup(login.get(url).content, 'html5lib')

   logging.info('Start to get login information')

   action = soup_login.find('form', id='fm1')['action']  # get login url

   logging.debug('action= ' + action)

   info = {}

   for element in soup_login.find('form').find_all('input'):

   for element in soup_login.find('form', id='fm1').find_all('input'):

      if element.has_attr('value'):

         info[element['name']] = element['value']

   logging.debug(info)

   logging.info('Login information acquired.')

   info['username'] = username

   info['password'] = password

   url = 'https://cas.sustc.edu.cn{}'.format(action)

   url = 'https://cas.sustc.edu.cn/cas/login?service={}'.format(url)

   logging.info('Login as ' + username)

   r = login.post(url, data=info, timeout=30)

   logging.info('Login information posted to the CAS server.')

   soup_response = BeautifulSoup(r.content, 'html5lib')

   success = soup_response.find('div', {'class': 'success'})

   err = soup_response.find('div', {'class': 'errors', 'id': 'msg'})

   return success, err

def test_network(url):

   try:

      test = login.get(url, timeout=30)

      content = test.content

      if test.status_code == 204:

      with login.get(url, timeout=10, allow_redirects=False) as test:

          if test.status_code == 200:

             status = CONNECTED

          elif test.status_code == 302:

             content = login.get(test.headers['Location'], timeout=10).content

             soup_login = BeautifulSoup(content, 'html5lib')

             if 'CAS' not in soup_login.title.string:

                logging.warning('Not connected to a SUSTC network')

                status = CONNECTED

             else:

                status = NEED_LOGIN

   except requests.Timeout:

          else:

             logging.warning('Recieved status code {code}, consider updating \'captive_portal_server\''.format(code=test.status_code))

             status = CONNECTION_TIMEOUT

   except requests.RequestException:

       status = CONNECTION_TIMEOUT

      content = None

   return status, content

   return status

def main():

   logging.info('Program started.')

   try:

      os.chdir(os.path.dirname(sys.argv[0]))  # To read config in the same directory

   except OSError:

      pass

   config = load_config()

   times_retry_login = config['max_times_retry_login']

   test_url = config['captive_portal_server']

   logging.info('Configurations successfully imported.')

   while True:

      logging.info('Checking network status...')

      status, content = test_network(test_url)

      status = test_network(test_url)

      if status == CONNECTION_TIMEOUT:

         logging.info('Connection FAILED. Try again in ' + str(config['interval_retry_connection']) + ' sec.')

         sleep(config['interval_retry_connection'])

         continue

      while status == NEED_LOGIN:

         soup_login = BeautifulSoup(content, 'html5lib')

         if 'CAS' not in soup_login.title.string:

            logging.warning('Not connected to a SUSTC network')

            sleep(config['interval_retry_connection'])

            continue

         times_retry_login -= 1

      elif status == CONNECTED:

         logging.info('You are already logged in.')

         break

      elif status == NEED_LOGIN:

         logging.info('You are offline. Starting login...')

         hostname = 'http://enet.10000.gd.cn:10001/sz/sz112/'

         if err:

            times_retry_login -= 1

            logging.error('Error occurred: ' + err.text)

            if times_retry_login > 0:

               # If keep trying to login too many times, it may trigger security alarm on the CAS server

               logging.info(

                  'Login FAILED. Try again in {time} sec. {attempt} attempt(s) remaining.'

                     .format(time=config['interval_retry_login'], attempt=times_retry_login))

            else:

               logging.info('Login FAILED. Attempts used up. The program will quit.')

               sys.exit(1)

            sleep(config['interval_retry_login'])

         elif success:

            logging.info('Login successful')

            times_retry_login = config['max_times_retry_login']

            logging.info('Login attempts reset to {attempt}.'.format(attempt=times_retry_login))

            break

      logging.info('Online. Re-check status in {time} sec.'.format(time=config['interval_check_status']))

      if times_retry_login > 0:

         # If keep trying to login too many times, it may trigger security alarm on the CAS server

         logging.info('Try again in {time} sec. {attempt} attempt(s) remaining.'.format(time=config['interval_retry_connection'], attempt=times_retry_login))

      else:

         logging.info('Attempts used up. The program will quit.')

         sys.exit(-1)

      sleep(config['interval_retry_connection'])

      sleep(config['interval_check_status'])

   logging.info('Online.')

   sys.exit(0)

if __name__ == '__main__':