[Twisted-Python] Problems using Twisted adbapi

[exarkun at divmod.com]

On Wed, 29 Sep 2004 23:47:37 +0200, Thomas Weholt <thomas.weholt at gmail.com> wrote:
>Hi,
> 
> My code below is an attempt to write a general database-abstraction
> layer for Twisted. I got one allready supporting SQLite and MySQL (
> MSSQL and PostgreSQL in the works ) but it blocks and doesn't use
> deffereds etc so I thought I'd try to write one that fits better with
> the Twisted framework. It will mainly be used in web-applications. The
> basic example is ( and don't laugh, this is my first attempt at using
> deferreds etc. ) :

  Hey Thomas,

    I think you're pretty close.  See below for a couple minor code changes.

> 
> from twisted.enterprise import adbapi
> 
> class TestConn:
> 
>     def __init__(self, dbname):
>         self.dbname = dbname
>         self.dbpool = adbapi.ConnectionPool("sqlite", db=dbname)
> 
>     def returnOk(self, o):
>         return True
> 
>     def returnFailure(self, o):
>         return False
> 
>     def returnResult(self, result):
>         return result
> 
>     def _returnResult(self, deferred, count = None):
>         if count:
>             return self.dbpool.fetchmany(count)
>         else:
>             return self.dbpool.fetchall()
> 
>     def execSql(self, sql, params = {}):
>         def run(sql, params):
>             return self.dbpool.runQuery(sql, params)
>         d = run(sql, params)
>         d.addCallback(self._returnResult)
>         d.addErrback(self.returnFailure)
>         d.addCallback(self.returnResult)
          return d
> 
>     def fetch(self, sql, params = {}):
>         def run(sql, params):
>             return self.dbpool.runQuery(sql, params)
>         d = run(sql, params)
>         d.addCallback(self.returnResult)
>         d.addErrback(self.returnFailure)
          return d
> 
> s = TestConn(r'c:\temp\db1.db')
> print s.execSql('create table table1 (a int, b int)')
> print s.execSql('insert into table1 (a,b) values (1,1)')
> print s.execSql('insert into table1 (a,b) values (1,2)')
> print s.execSql('insert into table1 (a,b) values (2,2)')
> print s.fetch('select * from table1')
> print s.fetch('select a from table1')
> 

  With the two added returns, you should no longer see None in the output, although you will also not see your actual results.  I think this is what you expected, though.

  Jp