如何以编程方式确定 ndb 属性是否为多值 [英] How to programmatically determine if ndb property is multivalue

问题描述

我正在将一个应用程序从 Datastore 转换为 ndb，并且在 xml 导入例程中遇到了问题.问题是我无法以编程方式确定 ndb.model 类的属性是否为多值属性.

I am translating an app from Datastore to ndb and have encountered a problem in the xml import routine. The problem is that I am not able to programmatically determine whether a property of a ndb.model class is a multivalue property or not.

我怀疑这是由于缺乏基本的 Python 技能，因为到目前为止我提出的代码表明该值是可见的".因此我无法抓住它.请帮忙.

I suspect that this is due to lack of basic Python skills since the code I have come up with so far shows that the value is "visible". I am thus not able to grab it. Please help.

from google.appengine.ext import ndb

class House(ndb.Model):
  name = ndb.StringProperty()   
  rooms = ndb.StringProperty(repeated=True) 

print 'Properties:'
for p in House._properties:
  print getattr(House,p)

print '\nRepeated:'
for p in House._properties:
  print getattr(getattr(House,p),'repeated',None)

结果如下:

Properties:
StringProperty('rooms', repeated=True)
StringProperty('name')

Repeated:
None
None

推荐答案

实际上，下划线前缀的选项是官方 API.这是他们没有记录的错误，我会修复它.我在这里解释了一点:http://code.google.com/p/appengine-ndb-experiment/issues/detail?id=187

Actually, the underscore-prefixed options are the official API. It's a bug that they aren't documented, I will fix that. I explained a little more here: http://code.google.com/p/appengine-ndb-experiment/issues/detail?id=187

特别是，要获取模型的属性，您应该使用 House._properties，而不是 Nick 提出的代码.(事实上​​，__dict__ 可能会在未来的 NDB 版本中被插槽替换.)

In particular, to get the properties of a model, you should use House._properties, not the code that Nick proposed. (In fact, __dict__ may be replaced with slots in future NDB versions.)

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