Django models API offers two similar options that usually cause confusion on many developers: null and blank . When I first started working with Django I couldn’t tell the difference and always ended up using both. Sometimes even using them improperly.
Both do almost the same thing, as the name suggests, but here is the difference:
Null : It is database-related. Defines if a given database column will accept null values or not. Blank : It is validation-related. It will be used during forms validation , when calling form.is_valid() .That being said, it is perfectly fine to have a field with null=True and blank=False . Meaning on the database level the field can be NULL , but in the application level it is a required field.
Now, where most developers get it wrong: Defining null=True for string-based fields such as CharField and TextField . Avoid doing that. Otherwise, you will end up having two possible values for “no data”, that is: None and an empty string . Having two possible values for “no data” is redundant. The Django convention is to use the empty string , not NULL .
So, if you want a string-based model field to be “nullable”, prefer doing that:
class Person(models.Model): name = models.CharField(max_length=255) # Mandatory bio = models.TextField(max_length=500, blank=True) # Optional (don't put null=True) birth_date = models.DateField(null=True, blank=True) # Optional (here you may add null=True)
The default values of null and blank are False .
Also there is a special case, when you need to accept NULL values for a BooleanField , use NullBooleanField instead.