[web2py] Problem trying to get a value from a rows object

[Christian Espinoza]

Hello, I'm trying to edit the group membership for a user, I have in my 
controller:

def change_membership():

    if request.vars.id:

        row = db(db.auth_membership.user_id == request.vars.id).select()
        id = row[0].id  
        form = SQLFORM(db.auth_membership,
                                   id,
                                   fields=['group_id'],
                                   _action=URL()
                                   )
    if form.process().accepted:
        ...redirect back to user list

    if form.errors:
        response.flash = 'form has errors'
    
    return dict(form=form)
 

But It doesn't work, I get a :
<type 'exceptions.IndexError'> list index out of range

I know that only get one row, but I don't understand why its seems empty..

Thanks in advance
Christian

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