How to store django objects as session variables ( object is not JSON serializable)?

Question

I have a simple view

def foo(request):
   card = Card.objects.latest(datetime)
   request.session[\'card\']=card

For the above code I get the

Answer 1

--> DON'T EVER FEEL LIKE DOING SOMETHING LIKE THIS! <--
Django using session and ctypes: Plz read Martijn Pieters explanation comment below.

class MyObject:
  def stuff(self):
    return "stuff..."

my_obj = MyObject()
request.session['id_my_obj'] = id(my_obj)

...

id_my_obj = request.session.get('id_my_obj')

import ctypes
obj = ctypes.cast(id_my_obj, ctypes.py_object).value

print(obj.stuff())    
# returns "stuff..."