Re: [SQLObject] Aggregate columns / change connection

[Andy T. <an...@ha...>]

Achim Domma (ProCoders) wrote:
> Hi,
> 
> I've seen Brad Bollenbach very good talk at Europython, and now I finaly
> found the time to give SQLObject a try. I really like it, but have some
> questions:
> 
> - In the examples, the connection is always hardcoded in the module, where
> my classes are definied. In real world apps I would like to specifiy the
> connection from outside of the module. I might have two different instances
> of my app, using two different servers/databases. How would I do that?
> 
> - What's about aggregate columns? I want to build a system with some kind of
> ranking mechanism, where I usually only want to show the average ranking. As
> far as I understand, I would have to calculate that value 'by hand', if I
> use SQLObject. Is that right?
> 
> regards,
> Achim
> 

I'll leave others to answer your question on aggregate columns, but for 
connections I do the same thing that I would for 'raw' db-api code.

I store the user name, password, host name and database name in a 
configuration file and then read that in at the top of my module. The 
values are placed in a dictionary (actually, they are stored in dict 
format but that's just because I'm lazy) and then used as arguments to 
the connection attribute. e.g.;

"""
import os.path
CONFIG_FILENAME='myconfig.txt'
if '__file__' in locals():
     CONFIG=os.path.dirname(__file__)+'/'+CONFIG_FILENAME
else:
	CONFIG=CONFIG_FILENAME
config=readAndEvalFile(CONFIG)

__connection__=MySQLConnection(db=config['db'], host=config['host'], 
user=config['user'], passwd=config['passwd'])
"""

The only magic there is the readAndEvalFile function which simply reads 
the file you supply and turns it into a dictionary.

Of course, you don't need to store the values in a configuration file. 
If you are building a web or gui front end to your application you can 
prompt for the values and then pass them in to your module at run time.

Regards,
Andy
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