Django Custom Save Model

Question

I am trying to do a basic date calculation in a save model in django, see below code:

class Purchase(models.Model): purchase_date = models.DateField() purchase_place = models.CharField(verbose_name='Place of Purchase', max_length=255) purchaseCategory = models.ForeignKey(PurchaseCategory, verbose_name='Purchase Category') cost = models.DecimalField(max_digits=11, decimal_places=2) warranty_period_number = models.IntegerField() warranty_period_type = models.CharField(max_length=255, choices=(('m', 'Month(s)'), ('y', 'Year(s)'))) warranty_end_date = models.DateField(editable=False) scan = models.CharField(max_length=255) alerts = models.BooleanField(verbose_name='Receive Email Alerts?') user = models.ForeignKey('auth.User', editable=False) created = models.DateTimeField(editable=False, auto_now_add=True) modified = models.DateTimeField(editable=False, auto_now=True) #custom save model def save(self, *args, **kwargs): #figure out warranty end date if self.warranty_period_type == 'm': self.warranty_end_date = self.purchase_date + self.purchase_date.timedelta(months=self.warranty_period_number) else: self.warranty_end_date = self.purchase_date + self.purchase_date.timedelta(years=self.warranty_period_number) super(Purchase, self).save() 

I thought the following would work, but no luck .. these are errors with:

 'datetime.date' object has no attribute 'timedelta' 

Can someone point in the right direction to do what I'm trying to do?

Cheers, Ben

Answer 1

timedelta does not take years, therefore

 from datetime import timedelta # custom save model def save(self, *args, **kwargs): # figure out warranty end date if self.warranty_period_type == 'm': self.warranty_end_date = self.purchase_date + timedelta(days=self.warranty_period_number*31) else: self.warranty_end_date = self.purchase_date + timedelta(days=self.warranty_period_number*365.2425) super(Purchase, self).save(*args, **kwargs) 

Refs Python timedelta in years