Mixin for watching field changes on Django models

diff_mixin.py

class DiffMixin:
    """
    Mixin for watching field changes

    Loads default/original attributes defined in the `watched_fields` list into the `originals` dict.
    Then we can check if a field has changed with the `has_field_changed` method.
    We can also get the original value of a field directly from the `originals` dict.

    Attributes:
        watched_fields (list): Class attribute with fields watched for changes.
        originals (dict): Instance attribute with original values of the fields.

    """

    watched_fields = []

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.originals = {}
        self.load_originals()

    def load_originals(self):
        for field in self.watched_fields:
            self.originals[field] = getattr(self, field)

    def has_field_changed(self, field):
        return self.originals[field] != getattr(self, field)

    def save(self, *args, **kwargs):
        super().save(*args, **kwargs)
        self.load_originals()