infinite if inside a loop

edit

I want to define a function that checks if a member of a set is another then print "well".

Let me explain it it the following example:

Assume that Z = Compositions(17, min_part=4).list(), L is some set and f is some function.

How I can write a function such that if f(a), where a is a member of Z, was in L, then that is "well"?

My attempt:

for i in in srange(len(Z)):
    for j in srange(i):
       if f(Z[i][j]) in L:

I don't know how to finish it because I just know finite if, else, not more.