diffmin.py

#!/usr/bin/env python
'''
Show lines in the second file that aren't in the first file to stdout.
All output that isn't file content goes to stderr.
'''
from __future__ import print_function
import sys


def echo0(*args, **kwargs):
    # PRint eRRoR
    print(*args, file=sys.stderr, **kwargs)
    return True

def usage():
    echo0(__doc__)

if len(sys.argv) < 3:
    usage()
    echo0("Error: You must specify two files.")
    exit(1)

# NOTE: sys.argv[0] is this script.
fName = sys.argv[1]
docDict = {}
count = 0
with open(fName, 'r') as f:
    for lineOriginal in f:
        if not lineOriginal:
            break
        line = lineOriginal.strip()
        docDict[line] = True
        count += 1
echo0("- read " + str(count) + " line(s)")

f2Name = sys.argv[2]

count = 0
newCount = 0
with open(f2Name, 'r') as f:
    echo0("Reading " + f2Name + "...")
    for lineOriginal in f:
        line = lineOriginal.strip()
        if docDict.get(line) is None:
            print(lineOriginal.rstrip())
            newCount += 1
        count += 1
echo0("- read " + str(count) + " line(s)")
echo0("- " + str(newCount) + " new line(s).")