[New-bugs-announce] [issue11354] argparse: nargs could accept range of options count

[Wojciech Muła]

New submission from Wojciech Muła <wojciech_mula at poczta.onet.pl>:

Hi, sometimes it is needed to grab variable, but limited, number of options.
For example --point could accept 2, 3 or 4 values: (x,y) or (x,y,z) or
(x,y,z,w). Current version of argparse requires postprocessing:

	parser.add_argument('--point', action='append', default=[])
	nmps = parser.parse_args()
	if not (2 <= len(nmsp.point) <= 4):
		raise argparse.ArgumentTypeError("--point expects 2, 3 or 4 values")

I propose to allow pass range of options count to nargs, including
lower/upper bound. For example:
	
	parser.add_argument('--point', nargs=(2,4) )	# from 2 to 4
	parser.add_argument('--foo', nargs=(9, None) )	# at least 9
	parser.add_argument('--bar', nargs=(None, 7) )	# at most 7
	nmsp = parser.parse_args()

I've attached tests and patch made against Python3.2 lib from Debian.

w.

----------
components: Library (Lib)
files: argparse-nargs.patch
keywords: patch
messages: 129714
nosy: wm
priority: normal
severity: normal
status: open
title: argparse: nargs could accept range of options count
type: feature request
versions: Python 3.2, Python 3.3
Added file: http://bugs.python.org/file20947/argparse-nargs.patch

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<http://bugs.python.org/issue11354>
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