BadValueError when updating ndb entity

Question

I am implementing a web application based on Google App Engine, Relying on ndb. I am facing a strange problem when trying to update one of the many entities in my db. When I try to update one of its properties (i.e. a string property) I get

&quot;/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/model.py&quot;, line 1715, in _validate (value,)) BadValueError: Expected string, got (u'a test',)

The same code works when I create a new entity of the same kind.

I know there will be soon someone asking me to add relevant code. It would be practically unreasonable to copy the javascript and python code I developed. I am interested to know if this behavior is known to occur in certain conditions I can check.

UPDATE

consider that the value with which I am trying to update the property is a post parameter (i.e. self.request.get('parameter'))

score 1 · Accepted Answer · answered Jan 27 '15 at 21:44

1

It looks to me like you are trying to assign a tuple to a model's ndb.StringProperty().

answered Jan 27 '15 at 21:44

mgilson

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it is a post parameter I am getting from the request – lowcoupling Jan 27 '15 at 21:45
@lowcoupling -- Can you check to make sure that it isn't coming in as a `tuple`? Without seeing your code, we can't do much more than guess... – mgilson Jan 27 '15 at 21:46
how can I check that? – lowcoupling Jan 27 '15 at 21:47
Find the line (in your code) (not ndb) where the exception is being raised and log the value just before you set it... – mgilson Jan 27 '15 at 21:48
Ok I have logged it and checked in the Log Console of Google App Engine. I see the string I expected. – lowcoupling Jan 27 '15 at 21:52
WOW I copied the code from the Entity creation where each property is separated by a comma. I didn't notice the comma remained at the end o the line ! You may want to update your answer – lowcoupling Jan 27 '15 at 21:56
So there you have it. It was a tuple ;-) – mgilson Jan 27 '15 at 21:57

BadValueError when updating ndb entity

1 Answers1