Detect if a model has changed before calling save in Django
You might try computing a checksum of the record values when you save them.  Then when you read it later, recompute the checksum and see if it has changed.  Perhaps the crc32 function in the Python zlib standard module.  (I'm not sure what kind of performance this would have.  So you may want to investigate that.)
I have a database model that is being updated based on changes in remote data (via an HTML scraper).
I want to maintain a field called changed - a timestamp denoting when the last time that model's values changed from what they were previously (note that this is different from auto_now as these fields are updated every time a model's save method is called).
Here is my question:
In a model's save method, is there a straightforward way to detect if a model instance's current values are different from the values in the database? Or, are there any alternative methods to easily maintain a changed timestamp?