added signal handler to automatically create an Account after a User got created

cash/models.py

@@ -1,10 +1,13 @@
 from django.db import models
 from django.contrib.auth.models import User
+from django.db.models.signals import post_save
+from django.dispatch import receiver
 
 
 class Account(models.Model):
 	user = models.OneToOneField(User)
-	card_number = models.CharField(max_length=32, unique=True, blank=True)
+	card_number = models.CharField(max_length=32, unique=True, blank=True,
+	                               null=True)
 	pin = models.CharField(max_length=32, blank=True)
 	daily_digest = models.BooleanField()
 	credit = models.IntegerField(default=0)
@@ -12,6 +15,12 @@ class Account(models.Model):
 	def __unicode__(self):
 		return self.user.username
 
+	@receiver(post_save, sender=User)
+	def user_post_save_handler(sender, **kwargs):
+		if kwargs['created']:
+			account = Account(user=kwargs['instance'])
+			account.save()
+
 	def buy_products(self, products):
 		# TODO place it somewhere else
 		MAX_DEBIT = -3500