def isCommaSeparatedEmailList(field_data, all_data):
 for supposed_email in field_data.split(','):
  try:
   isValidEmail(supposed_email.strip(), '')
  except ValidationError:
   raise ValidationError, gettext('Enter valid e-mail addresses separated by commas.')

def isCommaSeparatedEmailList ( field_data , all_data ) : for supposed_email in field_data . split ( ',' ) : try : isValidEmail ( supposed_email . strip ( ) , '' ) except ValidationError : raise ValidationError , gettext ( 'Enter valid e-mail addresses separated by commas.' )
checks that field_data is a string of e-mail addresses separated by commas .