Python argparse help formatter that keeps new lines and doesn't break words (so URLs are preserved), but still wraps lines. Use with: `argparse.ArgumentParser(formatter_class=SmartFormatter)`

smart_formatter.py

# Version 2:
# This version preserves space, including indentation.
#
# Also if you have lists like this:
#
#    foo ....... bla bla bla
#    bar baz ... bla bla bla bla
#
# It will re-formated it to e.g. this:
#
#    foo ....... bla bla
#                bla
#    bar baz ... bla bla
#                bla bla
# 
# This detects a sequence of >=3 periods or >=3 spaces.
#
# LICNESE: Public Domain/CC0

import argparse
import re

SPACE = re.compile(r'\s')
NON_SPACE = re.compile(r'\S')

class SmartFormatter(argparse.HelpFormatter):
    def _split_lines(self, text: str, width: int) -> list[str]:
        lines: list[str] = []
        for line_str in text.split('\n'):
            match = NON_SPACE.search(line_str)
            if not match:
                lines.append('')
                continue

            prefix = line_str[:match.start()]

            if len(prefix) >= width:
                lines.append('')
                prefix = ''

            line_len = prefix_len = len(prefix)
            line: list[str] = [prefix]
            pos = match.start()

            while pos < len(line_str):
                match = NON_SPACE.search(line_str, pos)
                if not match:
                    break

                next_pos = match.start()
                space = line_str[pos:next_pos]
                line_len += len(space)

                if line_len >= width:
                    lines.append(''.join(line))
                    line.clear()
                    line.append(prefix)
                    line_len = prefix_len
                else:
                    line.append(space)

                pos = next_pos
                match = SPACE.search(line_str, pos)
                if not match:
                    next_pos = len(line_str)
                else:
                    next_pos = match.start()

                word = line_str[pos:next_pos]
                word_len = len(word)
                line_len += word_len
                if line_len > width:
                    lines.append(''.join(line))
                    line.clear()
                    line.append(prefix)
                    line_len = prefix_len + word_len
                elif word_len >= 3:
                    if all(c == '.' for c in word) and line_str[next_pos:next_pos + 1].isspace():
                        prefix_len = line_len + 1
                        prefix = ' ' * prefix_len
                    elif all(c == ' ' for c in word):
                        prefix_len = line_len
                        prefix = ' ' * prefix_len
                line.append(word)
                pos = next_pos

            lines.append(''.join(line))
        return lines

    def _fill_text(self, text: str, width: int, indent: str) -> str:
        return '\n'.join(indent + line for line in self._split_lines(text, width - len(indent)))

Thanks for sharing this! You just saved me a ton of time!

Thank you so much for this!