EDIT: a solution is in this answer: How to use a dot “.” to access members of dictionary?
When using a dict:
d = dict()
d['param1'] = 17
d['param2'] = 3
it's easy to print it with  print json.dumps(d). When using an object / class:
class z: 
    pass
z.param1 = 17
z.param2 = 3
I can't manage to print all the attributes of z, neither with print json.dumps(z), nor with print z. How to do it?
Sidenote but important: why do I want to use a class / object to store parameters, when it would be logical to use a dict? Because z.param1 is much shorter and handy to write than z['param1'], especially with my (french) keyword [, ], 'are quit long to write because ALT+GR+5 (let's say 2 seconds instead of 0.5, but this really matters when you have a long code with many variables)
 
     
    