Justify a text using Python

justify.py

#! /usr/bin/env python3
# SPDX-License-Identifier: GPL-3.0
#
# Title: Justify text
# Author: Marcus Müller
# Copyright: 2024
#
# Usage: justify.py [width [file1] [file2] [file…]]
#
# if no files are specified, read from standard input
# if no width is specified, default to 90

import textwrap
import sys
import random
from typing import TextIO


def reflow_file(file_in: [str, TextIO], wrapper: textwrap.TextWrapper):
    random.seed(42)
    if type(file_in) is str:
        file_in = open(file_in, "r", encoding="utf-8")
    lines = wrapper.wrap(file_in.read())
    lines_out = []
    for lineno, line in enumerate(lines):
        if len(line) < wrapper.width and lineno != len(lines) - 1:
            words = line.split()
            spaces = len(words) - 1
            if spaces > 0:
                deficit = wrapper.width - len(line)
                if deficit >= spaces:
                    # we have more deficit than spaces
                    # so add to each word
                    n_add = deficit // spaces
                    words = [word + " " * n_add for word in words]
                    deficit = deficit - n_add * spaces
                choices = set(random.sample(range(spaces), k=deficit))

                words_out = []
                for idx, word in enumerate(words):
                    words_out.append(word)
                    if idx in choices:
                        words_out.append("")
                line = " ".join(words_out)
        lines_out.append(line)
    return "\n".join(lines_out)


if len(sys.argv) < 2:
    width = 90
    files = [sys.stdin]
elif len(sys.argv) < 3:
    width = int(sys.argv[1])
    files = [sys.stdin]
else:
    width = int(sys.argv[1])
    files = sys.argv[2:]

# set up the Text Wrapper. Add break_on_hyphens=False to the following
# arguments should you not want to allow breaking at every "-".

wrapper = textwrap.TextWrapper(width=width, tabsize=4)

lines = (reflow_file(f, wrapper) for f in files)
print("\n".join(lines))