Re: Strange error in django

[John DeRosa]

If you get an exception, the “except” clause will drop down into the “return” statement, and classification_serializer will be referenced before it’s assigned to. (Because it never was assigned to.)

John

On Apr 22, 2015, at 2:36 PM, Cristian Javier Martinez <martinezcri...@gmail.com> wrote:

Hi! I'm using the django rest framework and successfully deployed an application in a production environment but I'm having an strange error related to threads when I call a method that performs a simple classification task (using a scikit learn classifier) and I have no idea what is causing the error. This is the method in views.py

@api_view(['GET', 'POST'])
def classify_item(request):
        """
        Classify item, or list classifications.
        """
        if request.method == 'GET':
                items = Item.objects.all()
                serializer = ItemSerializer(items, many=True)
                return Response(serializer.data)

        elif request.method == 'POST':
                serializer = ItemSerializer(data=request.data['item'])
                if serializer.is_valid():
                        try:
                                item = serializer.data
                                filter_name = request.data['filter']


                                # fix encoding
                                item_dict =  {}
                                for key in item:
                                        value = item[key]
                                        if isinstance(value, unicode):
                                                value = value.encode('utf-8')
                                        item_dict[key] = value

                                classifier_name = CLASSIFIER_NAME_BY_FILTER[filter_name]

                                logger.debug("retrieving the persisted classifier and classifing the item")
                                clf = joblib.load(os.path.join(CLASSIFIERS_PATH, filter_name, classifier_name))

                                logger.debug("predicting probabilities")
                                data = pd.DataFrame([item_dict])

                                logger.debug("scoring item")
                                score = clf.predict(data)[0][1]

                                logger.debug("score: {}".format(score))


                                # create and save classification
                                classification = Classification(classifier_name=classifier_name,score=score,item_id=item['_id'])
                                classification_serializer = ClassificationSerializer(classification)
                                #classification_serializer.save()
                        except Exception as e:
                                logger.error("Ocurrio un error al intentar parsear el item: {}".format(e))
                        return Response(classification_serializer.data, status=status.HTTP_201_CREATED)

                return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

And the output is:

[22/Apr/2015 21:14:56] DEBUG [classifiers.views:63] retrieve the classifier for the given sited_id and classify item
[22/Apr/2015 21:15:14] DEBUG [classifiers.views:66] predicting probabilities
[22/Apr/2015 21:15:14] DEBUG [classifiers.views:69] scoring item
[22/Apr/2015 21:15:14] ERROR [classifiers.views:80] Ocurrio un error al intentar parsear el item: 'Thread' object has no attribute '_children'
[22/Apr/2015 21:15:14] ERROR [django.request:256] Internal Server Error: /items/
Traceback (most recent call last):
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/newrelic-2.50.0.39/newrelic/hooks/framework_django.py", line 499, in wrapper
    return wrapped(*args, **kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/newrelic-2.50.0.39/newrelic/hooks/component_djangorestframework.py", line 27, in _nr_wrapper_APIView_dispatch_
    return wrapped(*args, **kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/rest_framework/views.py", line 452, in dispatch
    response = self.handle_exception(exc)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/rest_framework/views.py", line 449, in dispatch
    response = handler(request, *args, **kwargs)
  File "/home/keepcon/meli_filters_env/local/lib/python2.7/site-packages/rest_framework/decorators.py", line 50, in handler
    return func(*args, **kwargs)
  File "/home/keepcon/meli_filters/classifiers/views.py", line 81, in classify_item
    return Response(classification_serializer.data, status=status.HTTP_201_CREATED)
UnboundLocalError: local variable 'classification_serializer' referenced before assignment

I was having an UnicodeEncodeError but I fixed it by adding "the fix encoding" step. I'll appreciate any cue about what could be causing this error, I don't understand why the error says something about threads since I'm not using threads.

Thanks in advance!

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users...@googlegroups.com.
To post to this group, send email to django...@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/da84ec7a-24a2-46b5-8d72-2d46c2d5a304%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[John DeRosa]

Oh, sorry.

Well, you’re using joblib. The joblib.load() call loads something and return a Python object into the symbol clf.

It would seem you need to look at the object that joblib.load is reconstituting. This code snippet doesn’t give enough information to diagnose this, but if I were you, I’d probably try this:

1. What file does "joblib.load(os.path.join(CLASSIFIERS_PATH, filter_name, classifier_name))” read, and what object does it return?

2. Can you interactively run this code in the Python interpreter? Does it run OK, or does it throw an exception?

3. If it works on your development machine, try running it interactively on your production machine. Ssh into your production server and run the code.

4. What does dir(clf) return? Does the clf object have the methods you expect it to have?

If you can get it to throw an exception when you run it from the interactive prompt, you can single-step it.

John

On Apr 22, 2015, at 4:10 PM, Cristian Javier Martinez <martinezcri...@gmail.com> wrote:

Thanks for your reply John DeRosa but the question is about what is causing the exception because I'm not using threads at all and the error says "'Thread' object has no attribute '_children'". I'm catching the error and printing it out before the return as you can see in the log.

To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/d38108d0-eda7-4e9e-9723-793a3290e030%40googlegroups.com.