On 7/2/14, 10:21 AM, trusted...@gmail.com wrote:
> Hi Michael, thank you for the answer.
> Both classes are in the same file so I don't see how it could be
> possible that one class is used while other is not imported.
> Could you help me with that ?
that would mean you're doing something that is invoking Artwork as a
mapped class and causing the mapper config step to occur before it gets
down to Person. The stack trace here would show exactly where that
originates.
>
> Andrey
>
> вторник, 1 июля 2014 г., 21:05:11 UTC+3 пользователь Michael Bayer
> написал:
>
>
> On 7/1/14, 1:17 PM, trust...@gmail.com <javascript:> wrote:
>> I have two classes, Artwork and Person. Artwork has a relationship to
>> Person.
>> However, when I try to use them, I get an error thrown:
>>
>> InvalidRequestError: When initializing mapper
>> Mapper|Artwork|artwork, expression 'Person' failed to locate
>> a name ("name 'Person' is not defined"). If this is a class
>> name, consider adding this relationship() to the <class
>> 'model.Artwork'> class after both dependent classes have been
>> defined.
>>
>>
>>
>> Here are the classes themselves, defined in model/__init__.py
>> class Artwork(db.Model, SimpleSerializeMixin):
>> id = db.Column(db.Integer, primary_key=True)
>> ....
>> artist_id = db.Column(db.String(256), db.ForeignKey('person.sub'))
>> artist = db.relationship('Person', backref='artworks')
>>
>> class Person(db.Model, SimpleSerializeMixin):
>> sub = db.Column(db.String(256), primary_key=True)
>>
>>
>> I checked with debugger and in
>> sqlalchemy/ext/declarative/clsregistry.py
>> (_class_resolver.__call__())
>> there is a line:
>> x = eval(self.arg, globals(), self._dict)
>> No "Person" or "Artwork" or any other class defined in the file
>> are present in globals(). self._dict is empty
>> So it fails with an NameError exception.
>>
>> What could be the issue ?
>
> it's usually that the Person code wasn't run, e.g. that the module
> in which it is located was not imported, before you tried to use
> the Artwork class. All the tables/classes can be introduced to
> the Python interpreter in any order, but once you try to "use" the
> mapping, e.g. make an object or run a query, it resolves all the
> links and everything has to be present.
>
>
>
>
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