[英]argparse: setting optional argument with value of mandatory argument
With Python's argparse , I would like to add an optional argument that, if not given, gets the value of another (mandatory) argument. 使用Python的argparse ,我想添加一个可选参数,如果没有给出,则获取另一个(强制)参数的值。
parser.add_argument('filename',
metavar = 'FILE',
type = str,
help = 'input file'
)
parser.add_argument('--extra-file', '-f',
metavar = 'ANOTHER_FILE',
type = str,
default = ,
help = 'complementary file (default: FILE)'
)
I could of course manually check for None
after the arguments are parsed, but isn't there a more pythonic way of doing this? 我当然可以在解析参数后手动检查
None
,但是不是有更多的pythonic方法吗?
As far as I know, there is no way to do this that is more clean than: 据我所知,除此之外没有办法做得更干净:
ns = parser.parse_args()
ns.extra_file = ns.extra_file if ns.extra_file else ns.filename
(just like you propose in your question). (就像你提出的问题一样)。
You could probably do some custom action gymnastics similar to this , but I really don't think that would be worthwhile (or "pythonic"). 你可能会做一些与此类似的自定义动作体操 ,但我真的不认为这是值得的(或“pythonic”)。
This has slightly different semantics than your original set of options, but may work for you: 这与原始选项集的语义略有不同,但可能对您有用:
parse.add_argument('filename', action='append', dest='filenames')
parse.add_argument('--extra-file', '-f', action='append', dest='filenames')
args = parse.parse_args()
This would replace args.filename
with a list args.filenames
of at least one file, with -f
appending its argument to that list. 这将使用至少一个文件的列表
args.filenames
替换args.filename
,其中-f
将其参数附加到该列表。 Since it's possible to specify -f
on the command line before the positional argument, you couldn't on any particular order of the input files in args.filenames
. 由于可以在位置参数之前在命令行上指定
-f
,因此您无法在args.filenames
输入文件的任何特定顺序。
Another option would be to dispense with the -f
option and make filename
a multi-valued positional argument: 另一种选择是省去
-f
选项并使filename
成为多值位置参数:
parse.add_argument('filenames', nargs='+')
Again, args.filenames
would be a list of at least one filename. 同样,
args.filenames
将是至少一个文件名的列表。 This would also interfere if you have other positional arguments for your script. 如果你的脚本有其他位置参数,这也会干扰。
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