Tracking dirty fields on a Django model instance

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Tracking dirty fields on a Django model instance.

$ pip install django-dirtyfields

or if you’re interested in developing it

$ virtualenv --no-site-packages ve/
$ source ve/bin/activate
(ve)$ pip install -r requirements.pip
(ve)$ python setup.py develop
(ve)$ cd example_app && ./manage.py test testing_app

Makes a Mixing available that will give you the methods:

  • is_dirty()

  • get_dirty_fields()

Using the Mixin in the Model

from django.db import models
from dirtyfields import DirtyFieldsMixin

class TestModel(DirtyFieldsMixin, models.Model):
    """A simple test model to test dirty fields mixin with"""
    boolean = models.BooleanField(default=True)
    characters = models.CharField(blank=True, max_length=80)

Using it in the shell

(ve)$ ./manage.py shell
>>> from testing_app.models import TestModel
>>> tm = TestModel(boolean=True,characters="testing")
>>> tm.save()
>>> tm.is_dirty()
False
>>> tm.get_dirty_fields()
{}
>>> tm.boolean = False
>>> tm.is_dirty()
True
>>> tm.get_dirty_fields()
{'boolean': True}
>>> tm.characters = "have changed"
>>> tm.is_dirty()
True
>>> tm.get_dirty_fields()
{'boolean': True, 'characters': 'testing'}
>>> tm.save()
>>> tm.is_dirty()
False
>>> tm.get_dirty_fields()
{}
>>>

Why would you want this?

When using signals, especially pre_save, it is useful to be able to see what fields have changed or not. A signal could change its behaviour depending on whether a specific field has changed, whereas otherwise, you only could work on the event that the model’s save() method had been called.

Credits

This code has largely be adapted from what was made available at Stack Overflow.

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