from argparse import ArgumentParser
parser = ArgumentParser(description='test', formatter_class=SmartFormatter)
parser.add_argument('-g', choices=['a', 'b', 'g', 'd', 'e'], default='a',
    help=
    """R|Some option, where
 a = alpha
 b = beta
 g = gamma
 d = delta
 e = epsilon"""
    )
parser.parse_args()
Python argparse: How to insert newline in the help text?