setattr for secondary attribute

[Alex]

I apologize for asking  maybe a very trivial question.
I have a new class object A with slots. One of the slots is, for
example, object spam. Object spam, in turn, also has slots and one of
them is attribute eggs. I need to assign a new value to eggs. In other
words, I need to perform the following:

A.spam.eggs=newValue

The problem is that I have only a string s='spam.eggs' with which to
work, so I cannot write an expression written above. I tried to use
setattr:

setattr(A, s, newValue)

but this does not work. It says that object A does not have attribute
spam.eggs

How would you do it? TIA.