RE: [Zope] quick question - database connections in python methods & return types?

22 Feb 2001

      The query result is a tuple, with two items.  The first item in the
tuple is a list of dictionaries, which describe each column.  These
dictionaries have values for 'name', 'type', 'null', and 'width'.  These
values came from MySQL, as meta-information about the query results.
The second item in the outermost tuple contains the actual data.  This
is a list of rows, each row is a tuple that has a value for each column,
in the same order as the column description dictionaries.

So yes, the result is a combination of tuple, list, and dictionary.  If
these types are confusing, I would suggest reading some of the material
on www.python.org.

Sample query result:

id  | title
----|---------
1   | john
2   | greg

Written in python as a "result object":

result =
	(
		[
			{'name': 'id',    'type': 'NUMBER', 'null': 'NOT
NULL', 'width':  4},
			{'name': 'title', 'type': 'STRING', 'null': 'NOT
NULL', 'width': -1}
		],
		[
			(1, 'john'),
			(2, 'greg')
		]
	)

-Randy
...
-----Original Message-----
From: Lee [mailto:lee.reilly@ntlworld.com]
Sent: Wednesday, February 21, 2001 4:26 PM
To: zope@zope.org
Subject: [Zope] quick question - database connections in 
python methods
& return types?
Hi there,
I have a quick question that I need answered concerning the 
return types
of SQL queries executed in Python methods.
I am querying/updating a database using Python methods as follows:
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# make a database connection string
try:
    db_conn = self.MySQL_database_connection()
except Exception:
    return "A connection to the database could not be made. <a
href='./'>
    Recover</a>."
try:
    SQL = "some SELECT query"
    result=db_conn.query(SQL)
except Exception:
    return "The class could not be created.<a href='./'> Recover</a>."
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When this is executed and I "return result[1]" it outputs the 
data in a
format like:
[(1, 16, 9, 1)]
* return result[0] gives me:
[{'name': 'PRACTICALS', 'type': 's', 'null': None, 'width': None},
{'name': 'TUTORIALS', 'type': 's', 'null': None, 'width': None},
{'name': 'ASSIGNMENTS', 'type': 's', 'null': None, 'width': None},
{'name': 'BONUS', 'type': 's', 'null': None, 'width': None}]
- the exact details aren't neccessary here I think. At first I had
problems trying to use this data i.e. parse it an store it in 
an array,
list, etc. but I overcome that by by first converting "result" to a
string using `result[1]`.
I was just wondering how to classify the original return type? It is
*not* a list, tuple, array or combination of either so what is it?
I'm writing a report on my project you see and I can't say that my
method returns an *cough* *cough* value ;-)
Thanks very much in advance if you can help.
Cheers,
Lee
_______________________________________________
Zope maillist  -  Zope@zope.org
http://lists.zope.org/mailman/listinfo/zope
**   No cross posts or HTML encoding!  **
(Related lists - 
 http://lists.zope.org/mailman/listinfo/zope-announce
 http://lists.zope.org/mailman/listinfo/zope-dev )

RE: [Zope] quick question - database connections in python methods & return types?

Randall F. Kern