An extremely simple object-relational mapper for Python and PostgreSQL.
This ORM uses a very minimalistic approach. The general idea is that the database schema is defined elsewhere (writing the SQL directly, or using some specialized software), and all the transactions are implemented either as methods in sub-classes of "Database", or as stored procedures.
This ORM allows you to very easily:
- Implement complex database transactions
- Call stored procedures
- Do simple queries
For complex queries you should use database views and stored procedures that return tables. (This is exactly what they were invented for!)
Here is a quick example:
>>> from curiousorm import * >>> class TestDatabase(Database): ... def create_account(self, balance): ... return self.insert_account(balance=balance, __return='id') ... ... def increase_account_balance(self, account_id, amount): ... with self.Transaction(): ... account = self.select_account_for_update(id=account_id) ... if account == None: ... raise Exception('wrong account id') ... else: ... account.balance += amount ... account.update_row() ... ... def delete_account(self, account_id): ... with self.Transaction(): ... account = self.select_account_for_update(id=account_id) ... if account == None: ... raise Exception('wrong account id') ... elif account.balance != 0: ... raise Exception('nonzero account balance') ... else: ... account.delete_row() ... >>> db = TestDatabase('dbname=curiousorm_test') >>> db.execute('CREATE TABLE account (id serial, balance int)')  >>> account_id = db.create_account(10) >>> db.increase_account_balance(account_id, 100) >>> db.select_account_list() [Record(id=1, balance=110)] >>> a = db.select_account(id=1) >>> a.balance 110 >>> db.delete_account(1) Traceback (most recent call last): ... Exception: nonzero account balance >>> db.callproc_current_database() # calls a stored procedure u'curiousorm_test' >>> db.current_database() # calls the same stored procedure u'curiousorm_test' >>> db.current_database_list() # the same, but returns a list instead [Record(current_database=u'curiousorm_test')]
This ORM consists of less than 20KB of very clean, thread-safe code, so that it can be reviewed and understood with minimum effort. In fact, reading and understanding the code is the recommended way of mastering it.