[DB-SIG] pyformat Parameter Style

Chris Cogdon chris at cogdon.org
Sat May 10 12:05:40 EDT 2003

On Saturday, May 10, 2003, at 10:54 US/Pacific, M.-A. Lemburg wrote:

> The DB API says "Python extended format codes" meaning that all
> valid Python formatting codes (including their parameters) may
> be used.

That's very interesting. Looking at some of the code I have, using, for 
example %(key)d would not work, even if the parameter was an integer, 
because the API turns each and every single parameter into a string 
regardless of the type.

This code snippet  from pyPgSQL.PgSQL:

                 if len(parms) == 1 and \
                    (type(parms[0]) in [DictType, ListType, TupleType] 
or \
                     parms = _quoteall(parms[0])
                     parms = tuple(map(_quote, parms));
                 self.res = self.conn.conn.query(_qstr % parms)

Notice how the parameters are 'quoted' first (which will turn them ALL 
into strings), and THEN it's passed to the '%' operator. If you have 
any %d in there, you'll get a TypeError.

And, take this docstring from pyPgSQL:

        cursor.execute(query[, param1[, param2, ..., paramN])
             Execute a query, binding the parameters if they are passed. 
             binding syntax is the same as the '%' operator except that 
only %s
             [or %(name)s] should be used and the %s [or %(name)s] 
should not be
             quoted.  Any necessary quoting will be performed by the 

    ("`-/")_.-'"``-._        Chris Cogdon <chris at cogdon.org>
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