failing to print not matched lines from second file

[tester_V]

with open ('file_2','r') as l_few :    f2=l_few.readlines()sp23 = [s.split(',')[3].strip() for s in f2] # collect all the terms you need to comparewith open ('file_1','r') as f1:              for lf1 in f1:        lf1=lf1.strip()        sp1 = lf1.split(",")        if sp1[3] not in sp23:            print (lf1) # print the non-matching line

I really appreciate your help but the code does not print out anything...