Generating fake data to populate database

Question

I am trying to use factory boy and faker to generate some fake data for a website I am building. Here is my models.py:

# External Imports
from django.db import models
import uuid

# Internal Imports
from applications.models.application import Application
from users.models.user import User
from .session import Session

# Fake data
import factory
import factory.django
import factory.fuzzy
from datetime import datetime
from faker import Faker
from faker.providers import BaseProvider
import random


class ButtonClick(models.Model):
    """**Database model that tracks and saves button clicks for an application**
    """
    # identifier
    id = models.UUIDField(default=uuid.uuid4, primary_key=True, editable=False)

    # info
    button_name = models.CharField(max_length=128, null=True, blank=True)
    application = models.ForeignKey(
        Application, related_name='button_clicks', null=True, blank=True, on_delete=models.CASCADE)
    user = models.ForeignKey(
        User, related_name='button_clicks', null=True, blank=True,      on_delete=models.CASCADE)
    session = models.ForeignKey(
        Session, related_name='button_clicks', null=True, blank=True, on_delete=models.CASCADE)
        timestamp = models.DateTimeField(auto_now=True)

class Meta:
    db_table = 'button_clicks'
    ordering = ('-timestamp', )

def __str__(self):
    return f'{self.application} - {self.button_name}'

fake = Faker()
faker = Factory.create()


class ApplicationFactory(factory.DjangoModelFactory):
    class Meta:
        model = Application

    application = factory.LazyAttribute(lambda _: faker.word())


class FakeButtonClick(factory.django.DjangoModelFactory):
    class Meta:
        model = ButtonClick

    button_name = factory.Faker('first_name')
    application = factory.SubFactory(ApplicationFactory)
    user = factory.Faker('name')
    session = factory.Faker('random_int')
    timestamp = factory.Faker('date')

When I try to run the following code in the terminal, I get an error:

>>> from analytics.models.button_click import FakeButtonClick
>>> for _ in range(200): FakeButtonClick.create()
... 

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/base.py", line 564, in create
    return cls._generate(enums.CREATE_STRATEGY, kwargs)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/django.py", line 141, in _generate
    return super(DjangoModelFactory, cls)._generate(strategy, params)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/base.py", line 501, in _generate
    return step.build()
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/builder.py", line 279, in build
    kwargs=kwargs,
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/base.py", line 315, in instantiate
    return self.factory._create(model, *args, **kwargs)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/factory/django.py", line 185, in _create
    return manager.create(*args, **kwargs)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/django/db/models/manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/django/db/models/query.py", line 431, in create
    obj = self.model(**kwargs)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/django/db/models/base.py", line 482, in __init__
    _setattr(self, field.name, rel_obj)
  File "/Users/ryan/bloks/bloks-backend/venv/lib/python3.7/site-packages/django/db/models/fields/related_descriptors.py", line 219, in __set__
    self.field.remote_field.model._meta.object_name,
ValueError: Cannot assign "9714": "ButtonClick.application" must be a "Application" instance.

I have created some very simple data using factory boy and faker in the past but the traceback seems to be implying that I need to create an application instance within my FakeButtonClick class? I checked the documentation and application doesn’t appear to be an available instance for factory boy/faker. Do I need to create the instance myself? Maybe a subfactory?

django django rest framework factory boy faker python

Xelnor · Answer

Your ButtonClick model has 3 fields defined as a ForeignKey: application, user and session.
When you want to create a ButtonClick instance, Django requires that you provide a valid value to each field defined as a ForeignKey — here, this means providing either model instances or None (since those ForeignKey are nullable).
With FactoryBoy, this means that you'll have to:

Define a Factory class for each of these models.
Use a factory.SubFactory pointing to those factories for each of the fields.

An example would be:

class UserFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = User
    username = factory.Faker('username')

class SessionFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = Session
    uuid = factory.Faker('uuid4')
    user = factory.SubFactory(UserFactory)

class ApplicationFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = Application
    name = factory.Faker('name')

class ButtonClickFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = ButtonClick
    user = factory.SubFactory(UserFactory)
    # Ensure that click.user == click.session.user
    session = factory.SubFactory(SessionFactory, user=factory.SelfAttribute('..user'))
    application = factory.SubFactory(ApplicationFactory)

You can take a look at the docs.
By the way, with FactoryBoy's faker integration, you don't need to import it directly: factory.Faker('uuid4') is equivalent to faker.Faker().uuid4().

crimsonpython24 · Answer

Here's my database-populate file, probably may help you (a lot simpler than your file I believe):
# Don't change the format. Order matters!

import os
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'project.settings')

import django
django.setup()

import random
from faker import Faker

from todo.models import Todo

fakegen = Faker()

def populate(N = 10):
    for entry in range(N):
        fake_tmp = fakegen.catch_phrase()
        levels = ['important', 'normal', 'unimportant']

fake_title = fake_tmp if len(fake_tmp) <= 40 else (fake_tmp[:37] + '...')
        fake_desc = fakegen.sentence(nb_words=70)
        fake_level = levels[random.randint(0, 2)]

todo_item = Todo.objects.get_or_create(title=fake_title, desc=fake_desc, level=fake_level)

if __name__ == '__main__':
    print('Populating data...')
    populate(20)
    print('Populating complete')

Generating fake data to populate database

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