django - Assigning values to a query result already set up with a foreign key -

i have database of exhibition listings related foreign key database of venues take place. django templates access venue information in query results through listing.venue.name, listing.venue.url, , on.

however, exhibitions take place in temporary venues, , information stored in same database, in listing.temp_venue_url , such. because seems wasteful , sad put conditionals on templates, want move info temporary venues templates expecting info regular venues. didn't work:

def transfer_temp_values(listings):     listing in listings:         if listing.temp_venue:             listing.venue = venue             listing.venue.name = listing.temp_venue             listing.venue.url = listing.temp_venue_url             listing.venue.state = listing.temp_venue_state             listing.venue.location = listing.temp_venue_location 

the error surprised me:

valueerror @ /[...]/ cannot assign "<class 'myproject.gsa.models.venue'>": "exhibition.venue" must "venue" instance. 

i rather thought was. how go accomplishing this?

the error message because have assigned class venue listing, rather instance of it. need call class instance:

listing.venue = venue()