Re: auto escaping "NULL"

On Fri, 04 Dec 2009 09:56:51 +0100
Federico Di Gregorio <fog-NGVKUo/i/[email protected]> wrote:

> Il giorno gio, 03/12/2009 alle 18.24 -0500, Jacob Joseph ha scritto:
> > Hi.
> > Upon trying to insert NULL values into a double precision field, I
> > receive the error:
> > 
> > DataError: invalid input syntax for type double precision: "NULL"
> > LINE 4:         (2, -1, E'NULL', 1.11,
> > 
> > I'm using a statement like:
> > curs.execute("INSERT INTO foo (distance) VALUES (%(dist)s)",
> > {'dist': None})
> 
> That's the correct way and should work. The code you show us is not
> the code you're actually executing? ;)

Thank you all for your responses.  It's what I *thought* I was
executing, but some older code had helpfully converted the None to a
'NULL' string, already.

> > As a related question, what is the correct way to use the execute(s,
> > args) syntax, but *not* escape a particular variable?  Not so
> > infrequently, I'd like to use an argument to add an SQL command,
> > such as adding to a WHERE or specifying a field.
> 
> You should use the normal % operator to build a query string and then
> pass it to execute. If you really want to avoid quoting of a bound
> variable you can import psycopg2.extras and then wrap the variable in
> AsIs() (AsIs just call wrapped object's str() method):
> 
> curs.execute("INSERT INTO foo (distance) VALUES (%(dist)s)",
>              {'dist': AsIs("NULL")})
> 
> But note that this example is a bad use case bacause psycopg knows how
> to parse None and you should use AsIs only in very special cases (and
> then be ashamed of it.)

Thanks.  I'll use it with trepidation.

~Jacob

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