Author: John Au-Yeung

Sometimes, we want to generate Python Django models from the database.

In this article, we’ll look at how to generate Python Django models from the database.

How to generate Python Django models from the database?

To generate Python Django models from the database, we run manage.py with the inspectdb option.

For instance, we run

python manage.py inspectdb > models.py

to make Django inspect the database the app is connected to, generate the models, and save the model class code to models.py.

Conclusion

To generate Python Django models from the database, we run manage.py with the inspectdb option.

Sometimes, we want to add a multiple choice field with Python Django.

In this article, we’ll look at how to add a multiple choice field with Python Django.

How to add a multiple choice field with Python Django?

To add a multiple choice field with Python Django, we can add a ManyToManyField.

For instance, we write

class Choices(models.Model):
  description = models.CharField(max_length=300)

class Profile(models.Model):
  user = models.ForeignKey(User, blank=True, unique=True, verbose_name='user')
  choices = models.ManyToManyField(Choices)

to create the choices field in the Profile model which is a ManyToManyField.

We use Choices as the argument to allow Choices values as the values for choices.

Conclusion

To add a multiple choice field with Python Django, we can add a ManyToManyField.

Sometimes, we want to perform query filtering in Python Django templates.

In this article, we’ll look at how to perform query filtering in Python Django templates.

How to perform query filtering in Python Django templates?

To perform query filtering in Python Django templates, we can create a template tag that calls filter.

For instance, we write

@register.filter
def in_category(things, category):
    return things.filter(category=category)

to create the in_category tag function that calls things.filter to filter by category.

Then we write

{% for category in categories %}
  {% for thing in things|in_category:category %}
    {{ thing }}
  {% endfor %}
{% endfor %}

in our template to use the in_category tag with the category as the value of the category parameter.

Conclusion

To perform query filtering in Python Django templates, we can create a template tag that calls filter.

Sometimes, we want to pass extra arguments to serializer Class in Python Django Rest Framework.

In this article, we’ll look at how to pass extra arguments to serializer Class in Python Django Rest Framework.

How to pass extra arguments to serializer Class in Python Django Rest Framework?

To pass extra arguments to serializer Class in Python Django Rest Framework, we set the context argument to a dict with the values we want to pass to the serializer.

For instance, we write

my_objects = MyModelSerializer(
    input_collection, 
    many=True, 
    context={'user_id': request.user.id}
).data

to create a MyModelSerializer by calling MyModelSerializer with the context argument set to a dict.

Then in our serializer class, we write

class MyModelSerializer(serializers.ModelSerializer):
    #...

    is_my_object = serializers.SerializerMethodField('_is_my_find')
    #...

    def _is_my_find(self, obj):
        user_id = self.context.get("user_id")
        if user_id:
            return user_id in obj.my_objects.values_list("user_id", flat=True)
        return False

to get the context values with self.context.get.

Conclusion

To pass extra arguments to serializer Class in Python Django Rest Framework, we set the context argument to a dict with the values we want to pass to the serializer.

Sometimes, we want to calculate the sum of the column values through query with Python Django.

In this article, we’ll look at how to calculate the sum of the column values through query with Python Django.

How to calculate the sum of the column values through query with Python Django?

To calculate the sum of the column values through query with Python Django, we can use the aggregate method.

For instance, we write

from django.db.models import Sum

ItemPrice.objects.aggregate(Sum('price'))

to call aggregate with the Sum('price') to create an aggregation result by summing up the price column value of each row.

Conclusion

To calculate the sum of the column values through query with Python Django, we can use the aggregate method.