gistfile1.pyw

def prepare(self):
    if not self.value or not self.value['end_datetime']:
        self.children.end_datetime.value = datetime.now() + timedelta(hours=1)
        
    self.children.program_owners.options = DBSession.query(ProgramOwner.program_owner_id, ProgramOwner.name).all()
    self.children.venues.options = DBSession.query(Venue.venue_id, Venue.name).all()
    self.children.users.options = [(u.user_id, u.fullname) for u in DBSession.query(User)]

    # THIS PART -v
    validatables = [self.children.program_owners, self.children.venues, self.children.users]
    for validatable in validatables:
        if isinstance(validatable.value, list) and isinstance(validatable.value[0], basestring) or \
            isinstance(validatable.value, basestring):
            validatable.value = validatable.validator._from_python(validatable.validator._to_python(validatable.value))
    
    return super(EventFields, self).prepare()