Compare two different files line by line in python

Question

I have two different files and I want to compare theirs contents line by line, and write their common contents in a different file. Note that both of them contain some blank spaces. Here is my pseudo code:

file1 = open('some_file_1.txt', 'r')
file2 = open('some_file_2.txt', 'r')
FO = open('some_output_file.txt', 'w')

for line1 in file1:
    for line2 in file2:
        if line1 == line2:
            FO.write("%s
" %(line1))

FO.close()
file1.close()
file2.close()

However, by doing this, I got lots of blank spaces in my FO file. Seems like common blank spaces are also written. I want to write only the text part. Can somebody please help me.

For example: my first file (file1) contains data:

Config:
Hostname = TUVALU

BT:
TS_Ball_Update_Threshold = 0.2

BT:
TS_Player_Search_Radius = 4

BT:
Ball_Template_Update = 0

while second file (file2) contains data:

Pole_ID      = 2
Width        = 1280
Height       = 1024
Color_Mode   = 0
Sensor_Scale = 1

Tracking_ROI_Size = 4
Ball_Template_Update = 0

If you notice, last two lines of each files are the same, hence, I want to write this file in my FO file. But, the problem with my approach is that, it writes the common blank space also. Should I use regex for this problem? I do not have experience with regex.

Answer 1

This solution reads both files in one pass, excludes blank lines, and prints common lines regardless of their position in the file:

with open('some_file_1.txt', 'r') as file1:
    with open('some_file_2.txt', 'r') as file2:
        same = set(file1).intersection(file2)

same.discard('
')

with open('some_output_file.txt', 'w') as file_out:
    for line in same:
        file_out.write(line)