TypeError: iterable argument required

[Νικόλαος Κούρας]

Hello, after inserting this line if "@" in mail and comment not in
("Σχολιάστε ή ρωτήστε με σχετικά....", ""):

iam getting the following error which i dont understand

**************************************************************
163         # insert guest comments into database if form was
submitted
  164         if "@" in mail and comment not in ("Σχολιάστε ή ρωτήστε
με σχετικά....", ""):
  165                 try:
  166                         cursor.execute( '''INSERT INTO
users(mail, comment) VALUES(%s, %s)''', (mail, comment) )
mail = None, comment = None

TypeError: iterable argument required
      args = ('iterable argument required',)
**************************************************************

can you help please?