How can I create an object and add attributes to it?

I want to create a dynamic object (inside another object) in Python and then add attributes to it.

I tried:

obj = someobject
obj.a = object()
setattr(obj.a, 'somefield', 'somevalue')

but this didn’t work.

Any ideas?

edit:

I am setting the attributes from a for loop which loops through a list of values, e.g.

params = ['attr1', 'attr2', 'attr3']
obj = someobject
obj.a = object()

for p in params:
   obj.a.p # where p comes from for loop variable

In the above example I would get obj.a.attr1, obj.a.attr2, obj.a.attr3.

I used the setattr function because I didn’t know how to do obj.a.NAME from a for loop.

How would I set the attribute based on the value of p in the example above?