Python argparse: How to insert newline in the help text?

Question

I'm using argparse in Python 2.7 for parsing input options. One of my options is a multiple choice. I want to make a list in its help text, e.g.

from argparse import ArgumentParser

parser = ArgumentParser(description='test')

parser.add_argument('-g', choices=['a', 'b', 'g', 'd', 'e'], default='a',

    help="Some option, where\n"

         " a = alpha\n"

         " b = beta\n"

         " g = gamma\n"

         " d = delta\n"

         " e = epsilon")

parser.parse_args()

However, argparse strips all newlines and consecutive spaces. The result looks like

~/Downloads:52$ python2.7 x.py -h

usage: x.py [-h] [-g {a,b,g,d,e}]

test

optional arguments:

  -h, --help      show this help message and exit

  -g {a,b,g,d,e}  Some option, where a = alpha b = beta g = gamma d = delta e

                  = epsilon

How do I insert newlines in the helptext.

Answer 1

Try using RawTextHelpFormatter here:

from argparse import RawTextHelpFormatter

parser = ArgumentParser(description='test', formatter_class=RawTextHelpFormatter)

Answer 2

The argparse module does strip out newlines in help text in Python 2.7. To maintain formatting with newlines you have to use the text wrap module to format.

Code:

from argparse import ArgumentParser
import textwrap

parser = ArgumentParser(description='test')
help_text = "Some option, where:\n" + \
"\n".join([
" a = alpha",
" b = beta",
" g = gamma",
" d = delta",
" e = epsilon"
])

help_text = textwrap.dedent(help_text)

parser.add_argument('-g', choices=['a', 'b', 'g', 'd', 'e'], default='a', help=help_text)
args = parser.parse_args()

In the above code help text is constructed using list of strings joined by new lines. This helps maintain the required format.