Print the cartesian product of the lines in FILE(s) multiplied with itself REPEAT times to standard output

permute.py

#!/usr/bin/env python3

import argparse
import itertools
import os
import sys


def positive_int(string):
    """Return a positive int from the argument string or raise an ArgumentTypeError"""
    try:
        value = int(string)
    except ValueError:
        msg = "invalid integer value: %r" % string
        raise argparse.ArgumentTypeError(msg)

    if not value > 0:
        msg = "invalid integer, must be greater than 0, received: %r" % string
        raise argparse.ArgumentTypeError(msg)

    return value


def main():
    parser = argparse.ArgumentParser(
        description="""
            Print the cartesian product of the lines in FILE(s) multiplied with itself REPEAT times to standard output.
        """
    )
    parser.add_argument(
        "repeat",
        type=positive_int,
        help="number of times to multiply the concatenation of FILE(s) with itself",
        metavar="REPEAT",
    )
    parser.add_argument(
        "files",
        nargs="*",
        type=argparse.FileType("r"),
        default=[sys.stdin],
        help="""files to read as input; with no FILE or when FILE is "-", standard input is read instead""",
        metavar="FILE",
    )
    parser.add_argument(
        "-s",
        "--separator",
        default="",
        help="optional string used to delimit the elements in each permutation",
    )
    args = parser.parse_args()

    # https://docs.python.org/3/library/signal.html#note-on-sigpipe
    try:
        lines = [line.rstrip("\n") for file in args.files for line in file]

        for permutation in itertools.product(lines, repeat=args.repeat):
            print(args.separator.join(permutation))

        sys.stdout.flush()
    except BrokenPipeError:
        devnull = os.open(os.devnull, os.O_WRONLY)
        os.dup2(devnull, sys.stdout.fileno())
        sys.exit(1)


if __name__ == "__main__":
    main()