Question

I have this class:

class Contract(db.Model):
    book_number = db.IntegerProperty(required = True)
    initial_page = db.IntegerProperty(required = True)
    final_page = db.IntegerProperty(required = True)
    contract_type = db.StringProperty(required = True)
    parties = db.ListProperty(str)
    date = db.DateTimeProperty (required = True, auto_now = True, auto_now_add = True)

And at this line of my code:

 contract.parties = old_parties.append([str(person_id), person_condition])

From this block:

        (...)
        party = []
        contract_record = Contract(book_number = int(numBook),
                                   initial_page = int(numInitialPage),
                                   final_page = int(numFinalPage),
                                   contract_type = choosed_contract_type,
                                   parties = party)
        contract_record.put()
        contract_key = contract_record.key()
        contract_id = contract_record.key().id()

        submit_button = self.request.get('submit_button')

        if submit_button:
            if (person_name and valid_name(person_name)) and (user_SSN and valid_SSN(user_SSN)):
                person_record = Person(person_name = person_name,
                nacionality = user_nacionality,
                profession = user_profession,
                marital_status = user_marital_status,
                driver_license = int(user_driver_license),
                SSN = int(user_SSN),
                address = address)
                person_record.put()
                person_key = person_record.key()
                person_id = person_record.key().id()

                contract = Contract.get_by_id(contract_id)
                old_parties = contract.parties
                contract.parties = old_parties.append([str(person_id), person_condition])
                contract.put()

I got this error:

 File "C:\Users\Py\Desktop\contract\main.py", line 351, in post
    contract.parties = old_parties.append([str(person_id), person_condition])
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\db\__init__.py", line 614, in __set__
    value = self.validate(value)
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\db\__init__.py", line 3435, in validate
    value = super(ListProperty, self).validate(value)
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\db\__init__.py", line 641, in validate
    raise BadValueError('Property %s is required' % self.name)
BadValueError: Property parties is required

My goal is: create an object contract with a empty list in its parties property. After that, I’d like to append new lists [person_id, person_condition] to that empty list, this way: [ [person_id, person_condition], [person_id2, person_condition2],...]

I’d like to know what is producing this error and how to fix it to achieve my goal.

Thanks for any help!

Answer 1

I’m not sure if this is what’s causing the GAE engine you see, but append appends to the list in place and returns None. So you want to do contract.parties.append([str(person_id), person_condition]). The way you are doing it, you wind up setting contract.parties to None.