Code-Memo

Field Lookups

Basic Field Lookups

Field lookups are specified as keyword arguments to the filter(), exclude(), and get() methods. Each lookup argument takes the form field__lookup=value.

Basic Field Lookups

Suppose you have an Author model and you want to filter authors by name:

authors_named_john = Author.objects.filter(name='John')

Common Field Lookups

exact

Matches values exactly equal to the specified value.

authors_named_john = Author.objects.filter(name__exact='John')

iexact

Case-insensitive match.

authors_named_john = Author.objects.filter(name__iexact='john')

contains

Case-sensitive match for whether a value contains the specified substring.

authors_with_jo = Author.objects.filter(name__contains='Jo')

icontains

Case-insensitive match for whether a value contains the specified substring.

authors_with_jo = Author.objects.filter(name__icontains='jo')

in

Matches any of the values in the given list.

authors_named_john_or_jane = Author.objects.filter(name__in=['John', 'Jane'])

gt / gte

Matches values greater than / greater than or equal to the specified value.

authors_born_after_2000 = Author.objects.filter(birth_date__gt='2000-01-01')
authors_born_on_or_after_2000 = Author.objects.filter(birth_date__gte='2000-01-01')

lt / lte

Matches values less than / less than or equal to the specified value.

authors_born_before_2000 = Author.objects.filter(birth_date__lt='2000-01-01')
authors_born_on_or_before_2000 = Author.objects.filter(birth_date__lte='2000-01-01')

startswith / istartswith

Case-sensitive / case-insensitive match for whether a value starts with the specified prefix.

authors_starting_with_j = Author.objects.filter(name__startswith='J')
authors_starting_with_j = Author.objects.filter(name__istartswith='j')

endswith / iendswith

Case-sensitive / case-insensitive match for whether a value ends with the specified suffix.

authors_ending_with_n = Author.objects.filter(name__endswith='n')
authors_ending_with_n = Author.objects.filter(name__iendswith='n')

range

Matches values within the given range.

authors_born_in_1990s = Author.objects.filter(birth_date__range=['1990-01-01', '1999-12-31'])

isnull

Matches True or False based on whether a field is NULL or not.

authors_with_no_birth_date = Author.objects.filter(birth_date__isnull=True)

Combining Field Lookups with Q Objects

For more complex queries, you can combine field lookups using Q objects.

Retrieve authors named ‘John’ or born after January 1, 2000:

from django.db.models import Q

authors = Author.objects.filter(Q(name='John') | Q(birth_date__gt='2000-01-01'))

• Q(name='John') | Q(birth_date__gt='2000-01-01') retrieves authors with the name ‘John’ or born after January 1, 2000.

Negating Field Lookups

You can negate field lookups using the ~ operator with Q objects.

Retrieve authors not named ‘John’:

from django.db.models import Q

authors_not_named_john = Author.objects.filter(~Q(name='John'))

• ~Q(name='John') retrieves authors whose name is not ‘John’.