failing to print not matched lines from second file

[deanhystad]

Can still use a set. It will be more efficient than comparing strings. First build the set of strings you are looking for, then read in the second file and check against the set.

with open(DIR/'lines_to_look_for.txt', 'r') as file:
    lines = set([line.strip().split(',')[3] for line in file])

with open(DIR/'check_for_lines.txt', 'r') as file:
    for line in file:
        line = line.strip()
        if line.split(',')[3] in lines:
            print(f'{line} MATCH')
        else:
            print(f'{line} NO MATCH')