Functional 'zip' for text files

zip_texts.py

from argparse import ArgumentParser
from itertools import repeat
from pathlib import Path
import shutil


def main(args):
    invalid_sources = filter(lambda path: not path.is_file(), args["source"])
    if (source := next(invalid_sources, None)):
        print("Provided source doesn't exist: %s" % source.absolute())
        exit(1)

    lines = []

    while args["source"]:
        if not args["dest"].is_file():
            shutil.copy(args["source"].pop(0), args["dest"])

        with args["dest"].open() as fd_dst:
            while (line := fd_dst.readline().rstrip()):
                lines.append(line)

        if not lines:
            args["dest"].unlink()
            continue

        break

    for source in args["source"]:
        longest_line = max(len(line) for line in lines)

        with source.open() as fd_src:
            i = 0
            while (line := fd_src.readline().rstrip()):
                lines[(i, i < len(lines) or lines.append(""))[0]] += "".join(repeat(" ", longest_line - len(lines[i]) + 1)) + line
                i += 1

    args["dest"].write_text("\n".join(lines))


if __name__ == "__main__":
    parser = ArgumentParser()
    parser.add_argument("source", type=Path, nargs="+")
    parser.add_argument("--dest", type=Path, required=True)

    args = parser.parse_args().__dict__
    main(args)