factory-boy

Common errors

Warnings

Install compatibility verified last tested: 2026-05-12 v3.3.3 (up to date)

Imports

• Factory
  wrong

  from factory_boy import Factory

  correct

  import factory
  
  class MyFactory(factory.Factory): ...

  The primary `Factory` class is typically imported from the `factory` namespace.

• Faker

  import factory
  
  class MyFactory(factory.Factory):
      name = factory.Faker('name')

  Used for generating realistic, randomized data.

• Sequence

  import factory
  
  class MyFactory(factory.Factory):
      id = factory.Sequence(lambda n: n)

  Generates sequential values, often used for unique IDs.

• LazyAttribute

  import factory
  
  class MyFactory(factory.Factory):
      full_name = factory.LazyAttribute(lambda o: f'{o.first_name} {o.last_name}')

  Evaluates its argument when the object is built, often dependent on other attributes of the generated object.

• SubFactory

  import factory
  
  class UserFactory(factory.Factory): ...
  class ProfileFactory(factory.Factory):
      user = factory.SubFactory(UserFactory)

  Used to create and link related objects, calling another factory.

• DjangoModelFactory

  from factory.django import DjangoModelFactory
  
  class UserFactory(DjangoModelFactory):
      class Meta:
          model = User

  Specific factory for Django ORM models, automatically handling `save()` behavior during `create()`.

• SQLAlchemyModelFactory

  from factory.alchemy import SQLAlchemyModelFactory
  
  class UserFactory(SQLAlchemyModelFactory):
      class Meta:
          model = User
          sqlalchemy_session = db_session

  Specific factory for SQLAlchemy models, requiring a session object in `Meta.sqlalchemy_session`.

Quickstart last tested: 2026-04-24

Define a simple Python class and then create a `factory.Factory` subclass for it. Use `factory.Faker` for realistic data and `factory.LazyAttribute` for interdependent fields. Instances can be created by calling the factory, with keyword arguments overriding default attributes.

import factory

class User:
    def __init__(self, first_name, last_name, email, is_admin=False):
        self.first_name = first_name
        self.last_name = last_name
        self.email = email
        self.is_admin = is_admin

    def __str__(self):
        return f'{self.first_name} {self.last_name} ({self.email})'

class UserFactory(factory.Factory):
    class Meta:
        model = User

    first_name = factory.Faker('first_name')
    last_name = factory.Faker('last_name')
    email = factory.LazyAttribute(lambda o: f'{o.first_name}.{o.last_name}@example.com'.lower())
    is_admin = False

# Create a basic user
user = UserFactory()
print(f"Created user: {user}")

# Create an admin user
admin_user = UserFactory(is_admin=True)
print(f"Created admin user: {admin_user}")

# Create a user with specific name
specific_user = UserFactory(first_name='John', last_name='Doe')
print(f"Created specific user: {specific_user}")