Question

I need to store instances (or at least their state) in a database. The idea is that I should be able to re-create the instance on demand. Since I define the classes, I can choose how I would like to store the data.

Consider the following diagram, inheritance diagram:

                    A
                   / \
                  B   C
                 /\   /\
                D  E F  ...

The idea is that the instance can belong to any of those classes and can itself store other objects (that I have completely design control over).

My first thought is to store the state exclusively in a dictionary, dump the dictionary into a json and store it in the database. At run time, load json from the database convert it to dictionary, create an object passing in the dictionary that get’s setup and so on…

I’m not sure if that is a good approach, and also if there are any other issues that might crop up. I already came across one, where if you use myobj.dict you don’t actually get all the class’ parent’s attributes though…

Any suggestions?

Answer 1

There are several approaches. I don’t really think we can tell you from the information you’ve provided what the best approach for you is.

• You can use an ORM, like SQLAlchemy.
• You can use an object database.
• You could pickle your objects and store them in any relational database or datastore including shelve, which is included in the standard distribution.

These are the approaches I can think of off the top of my head. Only you can determine which one(s) fit your requirements and intention best.