我来这里寻找方法来获得ArgumentDefaultsHelpFormatter的行为，但与换行符和制表符荣誉。特洛伊的代码让我接近了，但最终的结果更简单一些:

class CustomArgumentFormatter(argparse.ArgumentDefaultsHelpFormatter):
    """
    Formats help text to honor newlines and tabs (and show default values).
    """

    # Match multiples of regular spaces only.
    _SPACE_MATCHER = re.compile(r' +', re.ASCII)

    def _split_lines(self, text, width):
        new_text = []
        for line in text.splitlines():
          # For each newline in the help message, replace any multiples of
          # whitespaces (due to indentation in source code) with one space.
          line = self._SPACE_MATCHER.sub(' ', line).rstrip()
          # Fit the line length to the console width
          new_text.extend(textwrap.wrap(line, width))
        return new_text

然后换行符和制表符将按预期出现:

parser = argparse.ArgumentParser(formatter_class=CustomArgumentFormatter)

parser.add_argument(
    '--ethernet_config', type=str, required=False, default=None,
    help='Path to a text file that specifies Ethernet network IP settings \
      to use on the board. For example: \
      \n\t ip=192.0.2.100 \
      \n\t subnet_mask=255.255.255.0 \
      \n\t gateway=192.0.2.1')

尝试使用RawTextHelpFormatter来保存所有的格式:

from argparse import RawTextHelpFormatter
parser = ArgumentParser(description='test', formatter_class=RawTextHelpFormatter)

它类似于RawDescriptionHelpFormatter，但不是只应用于描述和epilog, RawTextHelpFormatter也应用于所有帮助文本(包括参数)。

我承认我发现这是一个非常令人沮丧的经历，因为我看到很多解决方案，我在网上看到很多次这样的问题。但我发现这些解决方案对我来说太复杂了，我想分享我最简单的解决方案。

下面是演示的脚本:

#!/usr/bin/python3
import textwrap
from argparse import ArgumentParser, HelpFormatter

class RawFormatter(HelpFormatter):
    def _fill_text(self, text, width, indent):
        return "\n".join([textwrap.fill(line, width) for line in textwrap.indent(textwrap.dedent(text), indent).splitlines()])

program_descripton = f'''
    FunkyTool v1.0

    Created by the Funky Guy on January 1 2020
    Copyright 2020. All rights reserved.

    Licensed under The Hippocratic License 2.1
    https://firstdonoharm.dev/

    Distributed on an "AS IS" basis without warranties
    or conditions of any kind, either express or implied.

    USAGE:
    '''

parser = ArgumentParser(description=program_descripton, formatter_class=RawFormatter)
args = parser.parse_args()

下面是它在test.py中的样子:

$ ./test.py --help
usage: test.py [-h]

FunkyTool v1.0

Created by the Funky Guy on January 1 2020
Copyright 2020. All rights reserved.

Licensed under The Hippocratic License 2.1
https://firstdonoharm.dev/

Distributed on an "AS IS" basis without warranties
or conditions of any kind, either express or implied.

USAGE:

optional arguments:
  -h, --help  show this help message and exit

所以，所有原始描述中的基本格式都被整齐地保留了下来，我们不得不，唉，使用一个自定义格式化器，但它是一个联机程序。它可以写得更清楚:

class RawFormatter(HelpFormatter):
    def _fill_text(self, text, width, indent):
        text = textwrap.dedent(text)          # Strip the indent from the original python definition that plagues most of us.
        text = textwrap.indent(text, indent)  # Apply any requested indent.
        text = text.splitlines()              # Make a list of lines
        text = [textwrap.fill(line, width) for line in text] # Wrap each line 
        text = "\n".join(text)                # Join the lines again
        return text

但我自己更喜欢写在一行上。

如果存在默认值，以下python 3格式化器将追加默认值并保留行长。

from argparse import ArgumentParser, ArgumentDefaultsHelpFormatter, \ 
                     RawTextHelpFormatter
import textwrap

class CustomArgumentFormatter(ArgumentDefaultsHelpFormatter, RawTextHelpFormatter):
    """Formats argument help which maintains line length restrictions as well as appends default value if present."""

    def _split_lines(self, text, width):
        text = super()._split_lines(text, width)
        new_text = []

        # loop through all the lines to create the correct wrapping for each line segment.
        for line in text:
            if not line:
                # this would be a new line.
                new_text.append(line)
                continue

            # wrap the line's help segment which preserves new lines but ensures line lengths are
            # honored
            new_text.extend(textwrap.wrap(line, width))

        return new_text

然后用你的新格式化器创建你的参数解析器:

my_arg_parser = ArgumentParser(formatter_class=CustomArgumentFormatter)
# ... add your arguments ...
print(my_arg_parser.format_help())

迟到了12年，但我也需要这个。

OP要求在帮助(不是描述)中的新行，因此这里的解决方案实际上并不完全有效，因为如果一行比屏幕宽度长，那么它在包装时失去缩进(被包装到列1而不是保留帮助文本的缩进)，这看起来真的很难看，或空行被吞噬，这是我不想要的，因为我有时需要长帮助文本中的空行。

工作方案如下:

import textwrap

class CustomHelpFormatter(argparse.ArgumentDefaultsHelpFormatter):
    def _split_lines(self, text, width):
        wrapper = textwrap.TextWrapper(width=width)
        lines = []
        for line in text.splitlines():
            if len(line) > width:
                lines.extend(wrapper.wrap(line))
            else:
                lines.append(line)
        return lines

parser = argparse.ArgumentParser(formatter_class=CustomArgumentFormatter)

Bernd的回答非常有用，但不适用于参数帮助字符串。下面是它的一个扩展，适用于所有的帮助文本(遵循RawTextHelpFormatter的例子)。

WrappedNewlineFormatter是他最初的RawFormatter, WrappedNewlineFormatter将额外包装参数。

import argparse
import textwrap

class DescriptionWrappedNewlineFormatter(argparse.HelpFormatter):
    """An argparse formatter that:
    * preserves newlines (like argparse.RawDescriptionHelpFormatter),
    * removes leading indent (great for multiline strings),
    * and applies reasonable text wrapping.

    Source: https://stackoverflow.com/a/64102901/79125
    """
    def _fill_text(self, text, width, indent):
        # Strip the indent from the original python definition that plagues most of us.
        text = textwrap.dedent(text)
        text = textwrap.indent(text, indent)  # Apply any requested indent.
        text = text.splitlines()  # Make a list of lines
        text = [textwrap.fill(line, width) for line in text]  # Wrap each line
        text = "\n".join(text)  # Join the lines again
        return text


class WrappedNewlineFormatter(DescriptionWrappedNewlineFormatter):
    """An argparse formatter that:
    * preserves newlines (like argparse.RawTextHelpFormatter),
    * removes leading indent and applies reasonable text wrapping (like DescriptionWrappedNewlineFormatter),
    * applies to all help text (description, arguments, epilogue).
    """
    def _split_lines(self, text, width):
        # Allow multiline strings to have common leading indentation.
        text = textwrap.dedent(text)
        text = text.splitlines()
        lines = []
        for line in text:
            wrapped_lines = textwrap.fill(line, width).splitlines()
            lines.extend(subline for subline in wrapped_lines)
            if line:
                lines.append("")  # Preserve line breaks.
        return lines


if __name__ == "__main__":
    def demo_formatter(formatter):
        parser = argparse.ArgumentParser(
            description="""
                A program that does things.
                Lots of description that describes how the program works.

                very long lines are wrapped. very long lines are wrapped. very long lines are wrapped. very long lines are wrapped. very long lines are wrapped. very long lines are wrapped.

                existing wrapping will be preserved if within width. existing
                wrapping is preserved. existing wrapping will be preserved.
                existing wrapping is preserved. existing wrapping will be
                preserved. existing wrapping is preserved. existing wrapping
                will be preserved. existing wrapping is preserved unless it goes too long for the display width.
                """,
            formatter_class=formatter,
        )
        parser.add_argument(
            "--option",
            choices=[
                "red",
                "blue",
            ],
            help="""
                Lots of text describing different choices.
                    red: a warning colour
                    text on the next line

                    blue: a longer blah blah keeps going going going going going going going going going going
                """,
        )
        print("\n\nDemo for {}\n".format(formatter.__name__))
        parser.print_help()

    demo_formatter(DescriptionWrappedNewlineFormatter)
    demo_formatter(WrappedNewlineFormatter)

WrappedNewlineFormatter的演示输出

usage: arg.py [-h] [--option {red,blue}]

A program that does things.
Lots of description that describes how the program works.

very long lines are wrapped. very long lines are wrapped. very long lines are
wrapped. very long lines are wrapped. very long lines are wrapped. very long
lines are wrapped.

existing wrapping will be preserved if within width. existing
wrapping is preserved. existing wrapping will be preserved.
existing wrapping is preserved. existing wrapping will be
preserved. existing wrapping is preserved. existing wrapping
will be preserved. existing wrapping is preserved unless it goes too long for
the display width.

optional arguments:
  -h, --help           show this help message and exit
                       
  --option {red,blue}  Lots of text describing different choices.
                       
                           red: a warning colour
                       
                           text on the next line
                       
                           blue: a longer blah blah keeps going going going
                       going going going going going going going
                       

DescriptionWrappedNewlineFormatter的演示输出

usage: arg.py [-h] [--option {red,blue}]

A program that does things.
Lots of description that describes how the program works.

very long lines are wrapped. very long lines are wrapped. very long lines are
wrapped. very long lines are wrapped. very long lines are wrapped. very long
lines are wrapped.

existing wrapping will be preserved if within width. existing
wrapping is preserved. existing wrapping will be preserved.
existing wrapping is preserved. existing wrapping will be
preserved. existing wrapping is preserved. existing wrapping
will be preserved. existing wrapping is preserved unless it goes too long for
the display width.

optional arguments:
  -h, --help           show this help message and exit
  --option {red,blue}  Lots of text describing different choices. red: a
                       warning colour text on the next line blue: a longer
                       blah blah keeps going going going going going going
                       going going going going
                       ```