Django - compare a matching column from two Querysets/models?

Question

I have two models. sitesubnets and devicesubnets.

I would like to compare the two models so I can create two lists. one list will have matching subnets one will have non matching subnets across them

I have tried using set difference but as they are different models I don think it works

test queries:

sitesubnet_data = SiteSubnets.objects.filter(site_id=site_id)
devicesubnet_data = DeviceSubnets.objects.filter(device_id=device_id)

data = set(sitesubnet_data).difference(set(devicesubnet_data))

when I compare sitesubnet_data with data, they are the same

my models:

class SiteSubnets(models.Model):
    site = models.ForeignKey(SiteData, on_delete=models.CASCADE)
    subnet = models.ForeignKey(Subnets, on_delete=models.CASCADE)

    class Meta:
        verbose_name = "Site Subnets"
        verbose_name_plural = "Site Subnets"
        unique_together = ('site', 'subnet',)


class DeviceSubnets(models.Model):
    device = models.ForeignKey(DeviceData, on_delete=models.CASCADE)
    subnet = models.ForeignKey(Subnets, on_delete=models.CASCADE)

    class Meta:
        verbose_name = "Device Subnets"
        verbose_name_plural = "Device Subnets"
        unique_together = ('device', 'subnet',)  

Answer 1

As far as I know, we could only compare same class objects (model objects). So, You should generate two different queryset of Subnets class which is common to both models. So I found one possible solution for your question, which is

devicesubnet = Subnets.objects.filter(devicesubnets__device_id=device_id)
sitesubnet = Subnets.objects.filter(sitesubnets__site_id=site_id)
common_subnets = list(set(devicesubnet) & set(sitesubnet))

Here common_subnets will hold the result, which has common Subnets instances with both SiteSubnets model and DeviceSubnets model