On Oct 31, 2010, at 3:08 PM, Daniel Meier wrote:
> Hi list
>
> I have tried the examples in the ORM tutorial and I'm wondering how I
> can separate different models into own modules.
>
> Let's say I have a "BankAccount" model and a "BankCustomer" model. My
> idea would be to create two modules, bankaccount.py and
> bankcustomer.py, and a database handler that imports the necessary
> stuff from that modules.
>
> This is what I came up with: http://pastie.org/1262474
>
> Actually, it doesn't work because the database was not yet initiated
> (metadata.create_all). Where should I put that? Or is my idea of
> splitting up a bad one?
>
> Daniel
I also like to keep my models separated in separate Python modules, although if
there are closely related tables (such as a header and a detail table), I keep
them in the same module. The "trick" is to have them all inherit from the same
declarative_base class. I do this by simply having a separate module that
creates that class:
base.py
======
from sqlalchemy.ext.declarative import declarative_base
BASE = declarative_base()
======
I then import BASE into the individual modules that create the models.
I have discovered that when calling create_all(), it's only necessary to import
the model module and the declarative_base class files before doing the import
and create_all() will create all the tables that are imported. This is
convenient for creating temporary databases (I use SQLite in-memory databases
for testing).
create_test_database.py
===================
from name import Name
from system import System
from base import BASE
engine = create_engine('sqlite://')
BASE.metadata.create_all(bind=engine)
# populate with test data
====================
In my actual application there are many more tables, but for this instance of
testing, I only need the tables modeled by Name and System.
I hope this helps.
Mark
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