Quick and dirty python script for performing set operations on lines in files.

fileset.py

#!/usr/bin/env python

import argparse
import os

def parse_file(fname):
    with open(fname) as f:
        return set(line.strip() for line in f)

def print_set(s, count=False):
    if count:
        print len(s)
    else:
        print '\n'.join(s)

def parse_args():
    parser = argparse.ArgumentParser(description='''
    Perform set operations on the lines of two files
    ''')

    parser.add_argument('file', nargs=2, help='files to compare')
    parser.add_argument('-t', help='set operation to perform (default: intersection)',
        choices=('union', 'intersection', 'difference'),
        default='intersection')
    parser.add_argument('-c', help='count the number of resulting lines',
        action='store_true')

    args = parser.parse_args()
    for fname in args.file:
        if not os.path.exists(fname):
            parser.error('file not found: {}'.format(fname))

    return args

def main():
    args = parse_args()

    f1 = parse_file(args.file[0])
    f2 = parse_file(args.file[1])

    if args.t == 'union':
        print_set(f1.union(f2), args.c)
    elif args.t == 'intersection':
        print_set(f1.intersection(f2), args.c)
    elif args.t == 'difference':
        print_set(f1 - f2, args.c)

if __name__ == '__main__':
    main()