在2个文件中查找公共行，从file1写入公共行，从文件2写入非公共行

Question

I am trying to find common lines in file 1 and file 2. If the common line exists, i want to write the line from file 2, otherwise print the non common line from file 1. fin1 and fin2 are the file handles here. Its reading the lines fine and there are common lines but i am not getting anything at all in teh output file.

flag=0
list1=fin1.readlines()
list2=fin2.readlines()
for i in list1:
    for j in list2:
        if i.strip() in j.strip():
            frealout.write(j)
            flag=1
            break
    if flag==0:
        frealout.write(j)
    flag=0

Here is the input file structure file1

ckgridu1n0
top_vli_z399a

here is the input file structure 2

   input node          ckgridu1n0,  
         input node [195:0]  top_vli_z399a, 

Answer 1

if flag==0: frealout.write(j)

you write j value out of it's visibility scope. It really is not initialized at that point You should change j to i

if flag==0: frealout.write(i)

Answer 2

According to

otherwise print the non common line from file 1

I think you want to do

if flag==0:
    frealout.write(i)

instead of

if flag==0:
    frealout.write(j)