django-tracking-model 0.1.2

Track changes made to django model instance.

Django Tracking Model 🏁

Track changes made to your model's instance.
Changes are cleared on save.
This package is intented to be used mainly with signals.
Mutable fields (e.g. JSONField) are not handled with deepcopy to keep it fast and simple.
Meant to be model_utils's FieldTracker fast alternative.

Available on PyPi

Usage

from django.db import models
from tracking_model import TrackingModelMixin

# order matters
class Example(TrackingModelMixin, models.Model)
    text = models.TextField(null=True)
    myself = models.ForeignKey("self", null=True)
    array = models.ArrayField(TextField())

In [1]: e = Example.objects.create(id=1, text="Sample Text")
In [2]: e.tracker.changed, e.tracker.newly_created
Out[1]: ({}, True)

In [3]: e.text = "Different Text"
In [4]: e.tracker.changed
Out[2]: {"text": "Sample Text"}

In [5]: e.save()
In [6]: e.tracker.changed, e.tracker.newly_created
Out[3]: ({}, False)

DTM will also detect changes made to ForeignKey/OneToOne fields.

In [1]: Example.objects.create(myself=e)
In [2]: e.myself = None
In [3]: e.tracker.changed
Out[1]: {"myself_id": 1}

Because DTM does not handle mutable fields well, you handle them with copy/deepcopy.

In [1]: e = Example.objects.create(array=['I', 'am', 'your'])
In [2]: copied = copy(e.array)
In [3]: copied.append('father')
In [4]: e.array = copied
In [5]: e.tracker.changed
Out[1]: {'array': ['I', 'am', 'your']}

In [6]: e.array = ['Testing', 'is', 'the', 'future']  # in this case copy not needed

DTM works best with *_save signals.

def pre_save_example(instance, *args, **kwargs):
    # .create() does not populate .changed, we use newly_created
    if 'text' in instance.tracker.changed or instance.tracker.newly_created:
      if instance.text
          instance.array = instance.text.split()

pre_save.connect(pre_save_example, sender=Example)

In [1]: e = Example.objects.create(text='I am your father')
In [2]: e.refresh_from_db() # not needed
In [3]: e.array
Out[1]: ['I', 'am', 'your', 'father']

DTM handles deferred fields well.

In [1]: e = Example.objects.only('array').first()
In [2]: e.text = 'I am not your father' 
In [3]: e.tracker.changed
Out[4]: {'text': DeferredAttribute}

You can narrow choice of tracked fields. By default everything is tracked.

class Example(models.Model):
    TRACKED_FIELDS = ['first']
    first = models.TextField()
    second = models.TextField()

Requirements

• Python >= 2.7, <= 3.8
• Django >= 1.11, <= 3.0

Todo

• Tests could be more readable
• Signals decorators