I'm getting the error below, the error only happens when I add delay to process_upload function, otherwise it works without a problem.

Could someone explain what this error is, why its happening and any recommendations to resolve?

Error:

PicklingError at /contacts/upload/configurator/47/Can't pickle <type 'function'>: attribute lookup __builtin__.function failed

This is the view

 if request.method == 'POST':form = ConfiguratorForm(data=request.POST)# Send import to task.process_upload.delay(upload_id=upload.id, form=form)

This is the task

@task
def process_upload(upload_id, form):upload = Upload.objects.get(id=upload_id)upload.process(form=form)

Upload.process is within my model:

 def process(self, form):self.date_start_processing = timezone.now()import_this(data=self.filepath, extra_fields=[{'value': self.group_id, 'position': 5},{'value': self.uploaded_by.id, 'position': 6}], form=form)

Full trace:

Traceback:
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response115.                         response = callback(request, *callback_args, **callback_kwargs)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view25.                 return view_func(request, *args, **kwargs)
File "/Users/user/Documents/workspace/sms/contacts/views.py" in upload_configurator118.         process_upload.delay(upload_id=upload.id, form=form)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/celery/app/task.py" in delay357.         return self.apply_async(args, kwargs)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/celery/app/task.py" in apply_async472.                                      **options)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/celery/app/amqp.py" in publish_task249.             **kwargs
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/kombu/messaging.py" in publish157.             compression, headers)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/kombu/messaging.py" in _prepare233.              body) = encode(body, serializer=serializer)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/kombu/serialization.py" in encode161.         payload = encoder(data)
File "/Users/user/Documents/workspace/sms/django-env/lib/python2.7/site-packages/kombu/serialization.py" in dumps340.         return dumper(obj, protocol=pickle_protocol)Exception Type: PicklingError at /contacts/upload/configurator/47/
Exception Value: Can't pickle <type 'function'>: attribute lookup __builtin__.function failed

forms.py

COL_CHOICES = [('N/A', 'No Import'),('first_name', 'First Name'),('last_name', 'Last Name'),('company', 'Company'),('mobile', 'Mobile Number'),('email', 'Email Address'),]class ConfiguratorForm(forms.Form):col1 = forms.TypedChoiceField(choices=COL_CHOICES, initial='first_name')col2 = forms.TypedChoiceField(choices=COL_CHOICES, initial='first_name')col3 = forms.TypedChoiceField(choices=COL_CHOICES, initial='first_name')col4 = forms.TypedChoiceField(choices=COL_CHOICES, initial='first_name')

You don't provide your ConfiguratorForm's definition but anyway: async execution requires that your task's arguments are pickable, and obviously your form is not. You could possibly go the hard way and make it pickable but that's just a waste of time. The simple solution is don't pass the form, only pass the form's data (iow: request.POST.copy() but I'm not sure Querydict are pickable) - or better, first validate the form and only pass the form's cleaned_data, as there's no point in processing an invalid form.