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💡extra_fields in Django

extra_fields are used to add extra additional fields in the serializer. Mostly it is used in custom serializer.

✨ Let’s try to understand it 👇

eg. Suppose there are Student, College, and Subjects models.

class Student(models.Model):
id = models.AutoField(primary_key=True)
student_name = models.CharField(max_length=120)
age = models.IntegerField()

class College(models.Model):
id = models.AutoField(primary_key=True)
college_name = models.CharField(max_length=120)
student = models.ForeignKey(Student,
on_delete=models.CASCADE, null=True)

class Subjects(models.Model):
id = models.AutoField(primary_key=True)
subject_name = models.CharField(max_length=120)
student = models.ForeignKey(Student, on_delete=models.CASCADE, null=True)

If we want to access student and their college and subject information then we can access it by writing a custom serializer. If we want to avoid a custom serializer then use related_name.
Now we see custom serializer


class StudentSerializer(serializers.ModelSerializer):
college = serializers.SerializerMethodField()
subject = serializers.SerializerMethodField()

def get_college(self, obj):
college_queryset = College.object.filter(
college_list = []
for collage in college_queryset:
return college_list

def get_subject(self, obj):
subject_queryset = Subject.object.filter(
subject_list = []
for subject in subject_queryset:
return subject_list

class Meta:
model = Student
fields = '__all__'
extra_fields = ["college", "subject"]

📝 Note: When we write a custom serializer then must pass the custom serializer name (college, subject)in the fields. Otherwise, it gives an error

Usecase: If extra_fields is not used but we want to mention "college", "subject" custom serializer name then we need to manually write all Student fields and "college", "subject".


class Meta:
model = Student
fields = ("id", "student_name", "age", "college", "subject")

So simply use extra_fields so that it becomes easy to add extra fields in the serializer instead of writing all fields ✌️

Usecase Of model_to_dict:

  1. Import it
from django.forms import model_to_dict

model_to_dict is used to convert an instance to a dictionary.

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Shweta Pawar

Shweta Pawar

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