Question

我有这堂课：

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(int)
    date = db.DateTimeProperty (required = True, auto_now = True, auto_now_add = True)

class ContractingParty(db.Model):
    person = db.ReferenceProperty(Person, required=True, collection_name="party_to_contracts")
    contract = db.ReferenceProperty(Contract, required=True)
    condition = db.StringProperty()

我使用此代码创建名为Contract的实体，parties属性为空列表：

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

但我必须使用ContractingPerson授权的ID填充parties属性。因此，在代码的其他部分，我以这种方式提升parties实体的Contract属性：

contracting_party_record = ContractingParty(person = person_key,
                                                      contract = contract_key,
                                                      condition = get_condition)
contracting_party_record.put()
contracting_party_id = contracting_party_record.key().id()
contract = Contract.get_by_id(contract_id)
contract.parties.append(contracting_party_id)
#contract.parties.extend(contracting_party_id)
contract.put()

但是当我以这种方式查询数据存储区时：

parties = db.GqlQuery("SELECT * FROM ContractingParty WHERE contract =:c_key", c_key = contract_key).fetch(20)

我只获得了我创建的最后一个ContractingParty实体。似乎contract.parties.append(contracting_party_id)正在用新的列表替换旧列表。然后，我尝试使用contract.parties.extend(contracting_party_id)。但是，现在，我收到了这个错误：

File "C:\Users\Py\Desktop\contract\main.py", line 363, in post
    contract.parties.extend(contracting_party_id)
TypeError: 'long' object is not iterable

如何解决这个问题？

Answer 1

在contract.parties.append（contracting_party_id）之类的列表中附加项目不会替换以前的列表，它也不应该在您的情况下执行。

您要做的是使用append代替extend。

虽然extend期望迭代像其他列表一样，append会在列表中添加一个项目。

>>> l = [1,2,3]
>>> l.append(4)
>>> l
[1, 2, 3, 4] 

>>> l = [1,2,3]
>>> l.extend([4,5,6])
>>> l
[1, 2, 3, 4, 5, 6]
>>>

这里是文档：http://docs.python.org/tutorial/datastructures.html

如何更新添加新元素的数据存储ListProperty实体（不替换旧元素）？

1 个答案: