Question

How can I update a row in my database using add() ?

Here is the code I tried :

@view_config(route_name='doc_user_edit', renderer='doc/edit.mako')
def doc_user_edit(request):
    """ Edit a documentation page. """
    message = ""
    try:
        page = DBSession.query(Page).filter_by(title=request.matchdict['pagename']).first()
    except DBAPIError:
        return Response('An error occured while trying to contact the database', content_type='text/plain', status_int=500)

    if page is None:
        return HTTPNotFound('No such page')

    if 'form.submitted' in request.params:
        page = Page(request.params['title'], request.params['content'], datetime.now())
        DBSession.add(page)
        DBSession.commit()
        message = _('Page edited')

    return {'p':page,
            'm':message,
            'save_url': request.route_url('doc_user_edit', pagename=page.title),
    }  

Notes : DBSession is a scoped_session.

If the row is brand new (i.e. unique key “title” is not present), it correctly adds a new row with the values I passed to it.

But if the row is an existing one, it simply does… nothing. I’d like it to update the row with new values (i.e. values extracted from a form). How can I achieve that?

Answer 1

You don’t need to use add() at all (it’s only necessary for new objects). Simply modify the existing page object and then commit.

if 'form.submitted' in request.params:
    page.title = request.params['title']
    page.content = request.params['content']
    page.no_idea_what = datetime.now()
    DBSession.commit()

By the way, unless there is a really good reason to use localtime it’s better to store your timestamps in UTC.

---

Depending on how your site works you might want to combine the logic for edit and create though. It would basically look like this:

def do_edit_whatever(obj):
    # Populate the fields here
    if obj.id is None:
        db.session.add(obj)
    db.session.commit()

Then your view functions would call that function either with a new Page() or one that is already in the database.