Dejavu 1.3, a Python ORM

Robert Brewer fumanchu at
Fri Jan 21 08:08:35 CET 2005

The Dejavu Object-Relational Mapper (version 1.3) is now available and
in the public domain. Get it at svn://

Dejavu is an Object-Relational Mapper for Python applications. It is
designed to provide the "Model" third of an MVC application. Dejavu
avoids making decisions in the framework which are better left to
developers, and avoids forcing developers to make decisions which are
better left to deployers. In particular, deployers are allowed to mix
and match storage mechanisms, including how and when to cache objects in
memory, making it easier for deployers to tune applications to their
particular environment.

Dejavu provides:

1. A base Unit class for persisting objects to storage.
2. A base Unit Property class for persistent object attributes.
3. ID Sequencers.
4. Associations between Unit classes.
5. Unit Engines, Rules, and Collections.
6. Aggregation and analysis tools.

1. Expressions: pure Python Unit queries. This is perhaps the most
appealing feature of Dejavu. However, since it uses bytecode hacks,
Dejavu only runs on CPython.
2. Sandboxes, which serve as Identity Maps and per-connection caches.
Unit objects are "memorized" and "recalled" from a Sandbox, using
3. An Arena class for application-level data.

1. A base StorageManager class and specification. Unlike many ORMs,
Dejavu does not require you to have complete control of the back end.
2. Specific StorageManagers for:
   a. Microsoft SQL Server/MSDE via ADO.
   b. Microsoft Access (Jet) via ADO.
   c. PostgreSQL.
   d. MySQL.
   e. SQLite.
   f. ODBC databases (not complete, and probably never will be).
   g. Shelve to dbm.

Major changes from 1.2:
1. Support for PostgreSQL, MySQL, and SQLite.
2. New db module which abstracts common DB StorageManager code.
3. Full support for decimal and fixedpoint.
4. brings common tests to all StorageManagers.

Dejavu welcomes your use and feedback as an application developer.

Dejavu also welcomes framework developers. New code for additional
Storage Managers, analysis tools, or other portions will be gladly
reviewed for inclusion in future releases. Drop me an email if you
feel so inclined.

Robert Brewer
Amor Ministries
fumanchu at

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