Query methods for the Django ORM

manager_querymethod.py

import models


class PersonManager(models.Manager):

    @models.querymethod
    def male(query):
        return query.filter(gender='m')

    @models.querymethod
    def female(query):
        return query.filter(gender='f')

    @models.querymethod
    def older_than(query, age):
        return query.filter(age__gte=age)

    @models.querymethod
    def younger_than(query, age):
        return query.filter(age__lt=age)


class Person(models.Model):

    GENDER_CHOICES = (
        ('m', 'Male'),
        ('f', 'Female'),
        ('o', 'Other'),
    )

    name = models.CharField(max_length=255)
    age = models.PositiveSmallIntegerField()
    gender = models.CharField(choices=GENDER_CHOICES, max_length=1)

    objects = PersonManager()


# Usage:

men = Person.objects.male()
minors = Person.objects.younger_than(18)
adults = Person.objects.older_than(18)
adult_men = men.older_than(18)

model_querymethod.py

import models


class Person(models.Model):

    GENDER_CHOICES = (
        ('m', 'Male'),
        ('f', 'Female'),
        ('o', 'Other'),
    )

    name = models.CharField(max_length=255)
    age = models.PositiveSmallIntegerField()
    gender = models.CharField(choices=GENDER_CHOICES, max_length=1)

    @models.querymethod
    def male(query):
        return query.filter(gender='m')

    @models.querymethod
    def female(query):
        return query.filter(gender='f')

    @models.querymethod
    def older_than(query, age):
        return query.filter(age__gte=age)

    @models.querymethod
    def younger_than(query, age):
        return query.filter(age__lt=age)


# Usage:

men = Person.objects.male()
minors = Person.objects.younger_than(18)
adults = Person.objects.older_than(18)
adult_men = men.older_than(18)

old_queryset_method.py

import models


class PersonQuerySet(models.QuerySet):

    def male(self):
        return self.filter(gender='m')

    def female(self):
        return self.filter(gender='f')

    def older_than(self, age):
        return self.filter(age__gte=age)

    def younger_than(self, age):
        return self.filter(age__lt=age)


class PersonManager(models.Manager):

    def get_query_set(self):
        return PersonQuerySet(model=self.model)

    def __getattr__(self, attr):
        return getattr(self.get_query_set(), attr)


class Person(models.Model):

    GENDER_CHOICES = (
        ('m', 'Male'),
        ('f', 'Female'),
        ('o', 'Other'),
    )

    name = models.CharField(max_length=255)
    age = models.PositiveSmallIntegerField()
    gender = models.CharField(choices=GENDER_CHOICES, max_length=1)

    objects = PersonManager()


# Usage:

men = Person.objects.male()
minors = Person.objects.younger_than(18)
adults = Person.objects.older_than(18)
adult_men = men.older_than(18)