Defaults and Empty Fields

Part of the Models and the Admin section of Coddy's Django journey. Lesson 3 of 23.

Save a book without saying whether you read it, and the database refuses: NOT NULL constraint failed. Every field is required until you say otherwise, with one of three options:

has_subtitles = models.BooleanField(default=True)
rating = models.DecimalField(max_digits=3, decimal_places=1, null=True, blank=True)
tagline = models.CharField(max_length=200, blank=True)

default is the value a new row gets when you give none. null=True lets the column store NULL, which Python reads as None. blank=True lets forms and the admin accept the field empty.

A number or a date you may not know needs both null=True and blank=True. Text needs only blank=True: empty text is stored as "", and null would give it two kinds of empty. TextField is text with no length limit, for something long like a review.

Challenge

Easy

Make the optional parts of Book optional:

is_read starts as False.
finished may be empty: an unfinished book has no date.
A new field summary: long text, no length limit, may be empty, the Django way for text.

Press Run, then in the Shell tab type Book.objects.create(title="Emma", author="Jane Austen", year=1815, price="7.50") and open the Data tab.

Try it yourself

from django.db import models


class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.CharField(max_length=100)
    year = models.IntegerField()
    price = models.DecimalField(max_digits=6, decimal_places=2)
    is_read = models.BooleanField()
    finished = models.DateField()