Tracking model changes in SQLAlchemy

Question

I want to log every action what will be done with some SQLAlchemy-Models.

So, I have a after_insert, after_delete and before_update hooks, where I will save previous and

Answer 1

If an attribute is expired (which sessions do by default on commit) the old value is not available unless it was loaded before being changed. You can see this with the inspection.

state = inspect(entity)
session.commit()
state.attrs.my_attribute.history  # History(added=None, unchanged=None, deleted=None)
# Load history manually
state.attrs.my_attribute.load_history()
state.attrs.my_attribute.history  # History(added=(), unchanged=['my_value'], deleted=())

In order for attributes to stay loaded you can not expire entities by settings expire_on_commit to False on the session.