ValueError: Cannot assign in django
Question: I have encountered a problem when I was trying to add/post a data to my
models. this is what i have done in my python manage.py shell:

    
    
    >>> from booking.models import *
    >>> qa = Product.objects.get(id=5)
    >>> sd = Booking.objects.create(
    ... date_select = '2011-11-29',
    ... product_name = qa.name,
    ... quantity = 1,
    ... price = qa.price,
    ... totalcost = 20,
    ... first_name = 'lalala',
    ... last_name = 'sadsd',
    ... contact = '2321321',
    ... product = qa.id)
    Traceback (most recent call last):
      File "<console>", line 10, in <module>
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 138, in create
        return self.get_query_set().create(**kwargs)
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 358, in create
        obj = self.model(**kwargs)
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 352, in __init__
        setattr(self, field.name, rel_obj)
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py", line 331, in __set__
        self.field.name, self.field.rel.to._meta.object_name))
    ValueError: Cannot assign "5": "Booking.product" must be a "Product" instance.
    

i don't have any idea why is that happening... it is `product = qa.id` not
equal to the Booking.product?

here is my model.py

    
    
    from django.db import models
    
    # Create your models here.
    class Product(models.Model):
        name = models.CharField(max_length=50, null=True, unique=False)
        quantity = models.IntegerField(max_length=10, null=True)
        price = models.FloatField()
        def __unicode__(self):
            return self.name
    
    class Booking(models.Model):
        date_select = models.DateField(auto_now=False, auto_now_add=False)
        product_name = models.CharField(max_length=50, blank=True, null=True)
        quantity = models.IntegerField(max_length=10, blank=True, null=True)
        price = models.FloatField()
        totalcost = models.FloatField()
        first_name = models.CharField(max_length=50, null=True, blank=True, unique=False)
        last_name = models.CharField(max_length=50, null=True, blank=True, unique=False)
        contact = models.CharField(max_length=50, null=True, blank=True, unique=False)
        product = models.ForeignKey(Product)
        def __unicode__(self):
            return self.first_name
    

and my handlers.py

    
    
    from django.utils.xmlutils import SimplerXMLGenerator
    from piston.handler import BaseHandler
    from booking.models import *
    from piston.utils import rc, require_mime, require_extended, validate
    class BookingHandler(BaseHandler):
        allowed_method = ('GET', 'POST', 'PUT', 'DELETE')
        fields = ('id', 'date_select', 'product_name', 'quantity', 'price','totalcost', 'first_name', 'last_name', 'contact', 'product')
        model = Booking
    
        def read(self, request, id):
            if not self.has_model():
                return rc.NOT_IMPLEMENTED
            try:
                inst = self.model.objects.get(id=id)
                return inst
            except self.model.MultipleObjectsReturned:
                return rc.DUPLICATE_ENTRY
            except self.model.DoesNotExist:
                return rc.NOT_HERE
    
        def create(self, request, *args, **kwargs):
            if not self.has_model():
                return rc.NOT_IMPLEMENTED
    
            attrs = self.flatten_dict(request.POST)
            if attrs.has_key('data'):
                ext_posted_data = SimplerXMLGenerator(request.POST.get('data'))
                attrs = self.flatten_dict(ext_posted_data)
            try:
                inst = self.model.objects.get(**attrs)
                return rc.DUPLICATE_ENTRY
            except self.model.DoesNotExist:
                inst = self.model(**attrs)#error??
                inst.save()
                return inst
            except self.model.MultipleObjectsReturned:
                return rc.DUPLICATE_ENTR
    

does anyone can give me a hand about my situation?

thanks in advance...


Answer: You assign the product as

    
    
    product = qa.id
    

While you should do

    
    
    product = qa
    

