Question

First of all,I’m not into web programming. I bumped into django and read a bit about models. I was intrigued by the following code ( from djangoproject.com ) :

 class Person(models.Model):     first_name = models.CharField(max_length=50)     last_name = models.CharField(max_length=50)      def __str__(self):         # Note use of django.utils.encoding.smart_str() here because         # first_name and last_name will be unicode strings.         return smart_str('%s %s' % (self.first_name, self.last_name)) 

By my understanding of python , first_name and last_name are class variables , right ? How is that used in code ( because I guess that setting Person.first_name or Person.last_name will affect all Person instances ) ? Why is it used that way ?

Answer 1

Yes, first_name and last_name are class variables. They define fields that will be created in a database table. There is a Person table that has first_name and last_name columns, so it makes sense for them to be at Class level at this point.

For more on models, see: http://docs.djangoproject.com/en/dev/topics/db/models/

When it comes to accessing instances of a Person in code, you are typically doing this via Django’s ORM, and at this point they essentially behave as instance variables.

For more on model instances, see: http://docs.djangoproject.com/en/dev/ref/models/instances/?from=olddocs