Designing models in django

Question

I'm working on my first django project that involves a student gradebook. Starting small, I'm just working on an app where teachers can upload students (student information - name and email address) and organize them into courses. My models so far are:

class Course(models.Model):
    course_name = models.CharField(max_length=20, default='Course')

    def __unicode__(self):
        return self.course_name


class Student(models.Model):
    course = models.ForeignKey(Course)
    name_text = models.CharField(max_length=40, default='First Last')
    email_address = models.EmailField(max_length=40, default='address@address.com')

    def __unicode__(self):
        return self.name_text

However, I'm not sure if the Course class is needed. I didn't think much of it, until I tried to create my first form where a user adds a student to the database. I had tried:

class StudentForm(forms.ModelForm):

    class Meta:
        model = Student
        fields= ('name_text',)

But this didn't work. I would get an error saying that the course field could not be null (null value in column "course_id" violates not-null constraint). So I modified to: fields ('course', 'name_text,). That worked.

This is what got me wondering if the Course class would actually be necessary. Ultimately I would like to be able to upload a text file with student names, parse the text to get the names (and email addresses) and create instances of the students. Only then would I assign the students to a course. But I get the feeling that the way I have my model setup right now will always insist that the student is assigned a course.

Should the class Course be kept?

Answer 1

If there is a 1-n relationship by student-course (many students in one course, a student in only one course) it's completely right.

Having a CharField instead that saves the course_name would eventually lead to inconsistencies (see db normalization, too), e.g. start off like this:

name_text | course_name
-----------------------
chris     | cs-101
doug      | cs-101

now cs-101 is renamed to cs-101-old and cs-101 is a new course with different topics. The db however still says we are both in new "new" course. If you have a ForeignKey to Courses you just change one value and the values in the students table change as well, since they are just pointers.

---

If you want the course to be optional just add a null=True to your ForeignKey declaration.

course = ForeignKey(Courses, null=True)