How to reference Python elixir object items

I am trying to swap in the key name from a request.param for an Elixir object attribute. Below, the Elixir object bk is a Book() which has an attribute PrintTitle. PrintTitle also comes in from a form as a request.param. Rather than manually map all the parameters to the Book attributes, I would like to map them based on a simple if in. However, it doesn't work, because I have the wrong syntax or method at bk.k.

if len(request.params) != 0:
        bk = Book()
        for k, v in request.params.items():
            print k, v # gives me love
            bk.k = v # no love here
        print 'Print Title:', bk.PrintTitle # value is None (obviously)

Solution

Unfortunately you can't just set the attribute of a Python object with a variable in this way. One way to do this is to use the setattr method to accomplish this, for example here is a crude example:

from elixir import *

metadata.bind = 'sqlite://'
metadata.bind.echo = False

class Book(Entity):
    PrintTitle = Field(String(50))

setup_all()
create_all()

params = {'PrintTitle':'Ethyl the Aardvark goes Quantity Surveying'}

bk = Book()

print "Title in database (before): {}".format(bk.PrintTitle)

for k, v in params.items():
    setattr(bk, k, v)

print "Title in database (after): {}".format(bk.PrintTitle)

The result of this script is:

Title in database (before): None
Title in database (after): Ethyl the Aardvark goes Quantity Surveying

Here I'm faking out your elixir model, and I'm just using a params dictionary to fake out whatever you're getting in request.params.

So in this example setattr(bk, k, v) is pretty much what you're trying to do with bk.k=v.

EDIT: I should add that you need to be careful using setattr, in that you need to be sure the key from your params exists in your db model first, as elixer/sqlalchemy may not like trying to set the value of a non-existent database field.