lookup in django

 

A lookup in Django is a way to filter the results of a query based on the value of a field. Django provides a number of built-in lookups, such as __exact, __gt, __lt, __in, and __contains. You can also create your own custom lookups.

To use a lookup, you need to specify the field name and the lookup name. For example, to filter for all users whose name is "John", you would use the following code:

Python

User.objects.filter(name__exact="John")

The lookup name is the part of the query that tells Django how to compare the value of the field. For example, the __exact lookup means that the value of the field must be exactly equal to the value you specify.

You can also use lookups to filter for values that are greater than, less than, or in a range. For example, the following code would filter for all users whose age is greater than 18:

Python

User.objects.filter(age__gt=18)

Django also provides a number of lookups that can be used to span relationships. For example, the following code would filter for all posts that were created by a user whose name is "John":

Python

Post.objects.filter(author__name="John")

The author__name lookup tells Django to follow the author relationship on the Post model and filter for posts where the name field of the author model is equal to "John".

For more information on lookups, please see the Django documentation: https://docs.djangoproject.com/en/4.2/topics/db/queries/.

Here are some of the most commonly used lookups in Django:

• __exact - The value of the field must be exactly equal to the value you specify.

• __gt - The value of the field must be greater than the value you specify.

• __lt - The value of the field must be less than the value you specify.

• __in - The value of the field must be one of the values you specify.

• __contains - The value of the field must contain the value you specify.

You can also use lookups to combine multiple conditions. For example, the following code would filter for all users whose name is "John" and whose age is greater than 18:

Python

User.objects.filter(name__exact="John", age__gt=18)

You can learn more about lookups in the Django documentation: https://docs.djangoproject.com/en/4.2/topics/db/queries/.