Creating view for update table via foregien key access in django - postgresql

Question

I am really new to django and stuck in using foreign key in django queries.Can anyone help me.
Situation:I created a sign up page with username and email field.So when a new user registered, its username and email address saved to auth_user table.
Q: I want to create a model instance in class UserDetails each time a new user register. or you can say entry of user as a foregien key in table userdetails. I am using postgresql database.
Myapp/models.py
class Pincode(models.Model):
pincode = models.CharField("PinCode",null=False)
geom = GeopositionField("Location")
objects = models.GeoManager()
def __unicode__(self):
return u'%s' %(self.pincode)
class UserDetails(models.Model):
user = models.OneToOneField(User, related_name='User_Details',unique=True)
pin= models.ForeignKey(Pincode,related_name='pin', null= True, blank=True)
rating= models.CharField(max_length=12, null=True, blank=True)
def __unicode__(self):
return u'%s, %s, %s' % (self.user, self.pin, self.rating)
views.py
def index(request):
update_user_details()
return render_to_response("larb/index.html",
RequestContext(request))
def update_user_details(request): ## **Stuck here**
user_details = UserDetails.objects.all()
new_entry= User.objects.exclude() # Don't know how to do
currently i am thinking of creating a function in the views that update the table.
first it checks for new entries means entries in auth_user which are not in userdetails table. If found update userdetails table.

Answer 1

I hope i solved it and it's seems fine now:
Here is views.py code
def index(request):
update_user_details()
return render_to_response("larb/index.html",
RequestContext(request))
def update_user_details():
id_past_entries = UserDetails.objects.all().values_list('user_id', flat = True)
new_entries = User.objects.exclude(id__in=id_past_entries)
if new_entries:
for new_id in new_entries:
new = User.objects.get(id=new_id)
UserDetails.objects.create(user=new)
UserDetails.save()