Again thanks for the suggestion. Using the low-level interface works
beautifully. I had to read the source code of appengine to figure out
wholly how to use it, but once that was done, I almost like the low-level
interface more than the high-level one. Entities behave like dictionaries
(plus the key field), simple translations to/from protocol buffers, etc.
The only weird thing is that for StringList properties, you cannot set the
StringList field to []: you need to set it to None.
This is kind of silly; they should have added an internal translation from
[] to None to make this transparent.
However, all my code works beautifully now, and I can get the benefits of
expando models without even having to worry about having expando models!
Luca
On Wednesday, July 10, 2013 9:03:07 AM UTC-7, Luca de Alfaro wrote:
>
> Thanks! This is a great suggestion; it might be the only one that works
> (short of giving up doing what I wanted to do in Python).
> The interesting thing is that the Java side has no trouble at all reading
> those entities.
>
> Luca
>
> On Wednesday, July 10, 2013 12:11:51 AM UTC-7, timh wrote:
>>
>> And here is some example code for getting and putting raw entities - ie
>> no model involved
>>
>> from google.appengine.api import datastorefrom google.appengine.api import
>> datastore_errorsdef get_entities(keys): rpc =
>> datastore.GetRpcFromKwargs({}) keys, multiple =
>> datastore.NormalizeAndTypeCheckKeys(keys) entities = None try:
>> entities = datastore.Get(keys, rpc=rpc) except
>> datastore_errors.EntityNotFoundError: assert not multiple
>> return entitiesdef put_entities(entities): rpc =
>> datastore.GetRpcFromKwargs({}) keys = datastore.Put(entities, rpc=rpc)
>> return keys
>>
>>
>> On Wednesday, July 10, 2013 3:09:56 PM UTC+8, timh wrote:
>>>
>>> Alternately make the property not required (required=False), load the
>>> entities set the value of the list to a [] and then rewrite, once you have
>>> migrated all the entities you can then
>>> set the property to be required.
>>>
>>> You do need to think about model migration when changing classes
>>> adding/removing or changing the types of properties.
>>>
>>> T
>>>
>>> On Wednesday, July 10, 2013 3:07:25 PM UTC+8, timh wrote:
>>>>
>>>> Have you tried setting the default value to [] as per that error ?
>>>>
>>>> If your model is blowing up you can always fetch the underlying data
>>>> without a model, fix the data up and write it back.
>>>>
>>>> T
>>>>
>>>> On Wednesday, July 10, 2013 9:56:50 AM UTC+8, Luca de Alfaro wrote:
>>>>>
>>>>> This is pretty bad!
>>>>>
>>>>> As pointed out in
>>>>> https://code.google.com/p/googleappengine/issues/detail?id=8962 , if
>>>>> you add a StringListProperty to a model with existing entities in the
>>>>> datastore, then you cannot read those entities any more!
>>>>> Furthermore, in Java it is apparently possible to write entities with
>>>>> null StringListProperty fields. Those entities cannot then be read from
>>>>> Python!
>>>>> These are pretty big problems -- is there any solution?
>>>>>
>>>>> Luca
>>>>>
>>>>> On Tuesday, March 23, 2010 5:57:17 AM UTC-7, Geoffrey Spear wrote:
>>>>>>
>>>>>> On Mar 22, 11:09 pm, dhruvbird <dhruvb...@gmail.com> wrote:
>>>>>> > Hello,
>>>>>> > I have a model with a single attribute that is a
>>>>>> StringListProperty.
>>>>>> > I get an error if I define it as such:
>>>>>> >
>>>>>> > class Test(db.Expando):
>>>>>> > people = db.StringListProperty(required=False, indexed=True)
>>>>>> >
>>>>>> > However, on changing it to:
>>>>>> > class Test(db.Expando):
>>>>>> > people = db.StringListProperty(required=True, indexed=True,
>>>>>> > default=[])
>>>>>> >
>>>>>> > It starts working. Any ideas why this is happening??
>>>>>>
>>>>>> ListPropertys are always required; you can't set their value to None.
>>>>>> If a particular entity has no values for the ListProperty, you need to
>>>>>> set it to the empty list. (Note that you can still set a default
>>>>>> value of 'None', which magically uses an empty list, not None, as the
>>>>>> default value.)
>>>>>>
>>>>>>
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