Django model error maximum recursion depth exceeded

Question

I'm following this guide and I get the following error when saving...

RuntimeError at /admin/products/product/2/
maximum recursion depth exceeded

Why do I get this error? I have included the full model below.

Thanks

models.py:

class Product(models.Model):
    title = models.CharField(max_length=60)
    qr_url = models.URLField(blank=True)
    qr_image = models.ImageField(
        upload_to="public/uploads/",
        height_field="qr_image_height",
        width_field="qr_image_width",
        null=True,
        blank=True,
        editable=False
    )
    qr_image_height = models.PositiveIntegerField(null=True, blank=True, editable=False)
    qr_image_width = models.PositiveIntegerField(null=True, blank=True, editable=False)

    #FK
    category = models.ManyToManyField(ProductCategory)
    attribute_answers = models.ManyToManyField(AttributeAnswers)
    # Custom Managers

    def __unicode__(self):
        return self.title

    def qr_code(self):
        return '' % self.qr_image.url
    qr_code.allow_tags = True

def product_pre_save(sender, instance, **kwargs):
    if not instance.pk:
        instance._QRCODE = True
    else:
        if hasattr(instance, '_QRCODE'):
            instance._QRCODE = False
        else:
            instance._QRCODE = True


models.signals.pre_save.connect(product_pre_save, sender=Product)


def product_post_save(sender, instance, **kwargs):
    if instance._QRCODE:
        instance._QRCODE = False
    if instance.qr_image:
        instance.qr_image.delete()
    qr = QRCode(4, QRErrorCorrectLevel.L)
    qr.addData(instance.qr_url)
    qr.make()
    image = qr.makeImage()

    #Save image to string buffer
    image_buffer = StringIO()
    image.save(image_buffer, format='JPEG')
    image_buffer.seek(0)

    #Here we use django file storage system to save the image.
    file_name = 'UrlQR_%s.jpg' % instance.id
    file_object = File(image_buffer, file_name)
    content_file = ContentFile(file_object.read())
    instance.qr_image.save(file_name, content_file, save=True)


models.signals.post_save.connect(product_post_save, sender=Product)

DrewM · Accepted Answer · 2013-02-19 16:57:13Z

5

Your post save signal call save which calls the post save signal which calls save ...

This is basically an infinite loop which the runtime kills with the Max Recursion error.

answered Feb 19, 2013 at 16:57

DrewM

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Comments

WBAR · Accepted Answer · 2013-02-19 17:08:35Z

You copiend in wrong way from tutorial :)

def product_post_save(sender, instance, **kwargs):
    if instance._QRCODE:
        instance._QRCODE = False
        if instance.qr_image:
            instance.qr_image.delete()
        qr = QRCode(4, QRErrorCorrectLevel.L)
        qr.addData(instance.qr_url)
        qr.make()
        image = qr.makeImage()

        #Save image to string buffer
        image_buffer = StringIO()
        image.save(image_buffer, format='JPEG')
        image_buffer.seek(0)

        #Here we use django file storage system to save the image.
        file_name = 'UrlQR_%s.jpg' % instance.id
        file_object = File(image_buffer, file_name)
        content_file = ContentFile(file_object.read())
        instance._already_saving = True
        instance.qr_image.save(file_name, content_file, save=True)

Kahbazi · Accepted Answer · 2016-07-03 08:13:43Z

0

To solve this problem, You should add one more field in database, this field will describe that inserted record is inserted by simple view or signal. then in receiver function you should check that if instance is inserted by signal if so don't apply receiver function

@receiver(post_save) def my_callback(using,sender,instance,**kwargs):
   if not(instance.added_by == 'signal'):
       obj = Student1()
       obj.name = instance.name
       obj.city = instance.city
       obj.state = instance.state
       obj.postal_code = instance.postal_code
       obj.age = instance.age
       obj.added_by = 'signal'
       obj.save()

edited Jul 3, 2016 at 8:13

Kahbazi

15.1k3 gold badges52 silver badges80 bronze badges

answered Jul 3, 2016 at 6:10

Arpit Singh

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1 Comment

Dat TT Over a year ago

This is not a good idea because you have to an extra field which is not used at elsewhere and you will have a migration for that model. And what if we need to do for 100+ models?

Dat TT · Accepted Answer · 2018-09-06 03:42:02Z

0

My approach is just to use udpate method of QuerySet object instead of save one from Model:

Model.objects.filter(pk=obj.pk).update(fieldx=valuey)

answered Sep 6, 2018 at 3:42

Dat TT

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