uSort

#!/usr/bin/env python3
# encoding: utf-8

from sys import argv, exit

# Source file parsing
def parse_list(filename):
    result = []

    with open(filename, 'r', encoding="UTF-8") as reader:
        for line in reader:
            clean_line = line.strip().lower()
            if clean_line:
                result.append(clean_line)

    return frozenset(result)

def write_list(lines, filename):
    with open(filename, 'w', encoding="UTF-8") as out_file:
        for line in sorted(lines):
            print(line, file=out_file)

if __name__ == "__main__":
    # Parsing arguments
    try:
       source_file = argv[1]
    except IndexError:
       print("You must supply the input file!")
       exit(1)

    try:
        destination_file = argv[2]
    except IndexError:
        destination_file = source_file

    lines = parse_list(source_file)
    write_list(lines, destination_file)