Python中使用argparse的条件命令行参数

I'd like to have a program that takes a --action= flag, where the valid choices are dump and upload, with upload being the default. If (and only if) dump is selected, I'd like there to also be a --dump-format= option. Is there a way to express this using argparse, or do I need to just accept all the arguments and do the logic myself.

我想要一个带有--action =标志的程序,其中有效的选择是转储和上传,上传是默认的。如果(并且仅当)选择了dump,我希望还有--dump-format =选项。有没有办法用argparse表达这个,或者我需要接受所有的参数并自己做逻辑。

3 个解决方案

#1

You could use parser.error:

你可以使用parser.error:

import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--action', choices=['upload', 'dump'], default='dump')
parser.add_argument('--dump-format')
args = parser.parse_args()
if args.action != 'dump' and args.dump_format:
    parser.error('--dump-format can only be set when --action=dump.')

#2

Another way to approach the problem is by using subcommands (a'la git) with "action" as the first argument:

解决问题的另一种方法是使用子命令(a'la git)和“action”作为第一个参数:

script dump --dump-format="foo"
script upload

#3

The argparse module offers a way to do this without implementing your own requiredness checks. The example below uses "subparsers" or "sub commands". I've implemented a subparser for "dump" and one for "format".

argparse模块提供了一种方法,无需执行自己的必要性检查。以下示例使用“subparsers”或“sub commands”。我为“转储”实现了一个subparser,为“format”实现了一个subparser。

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('file', help='The file you want to act on.')
subparsers = parser.add_subparsers(dest='subcommand')

#  subparser for dump
parser_dump = subparsers.add_parser('dump')
# add a required argument
parser_dump.add_argument(
    'format',
    choices=['csv', 'json'],
    help='Dump the file in this format.')

#  subparser for upload
parser_upload = subparsers.add_parser('upload')
# add a required argument
parser_upload.add_argument(
    'server',
    choices=['amazon', 'imgur'],
    help='Upload the file to this service.')

args = parser.parse_args()
print args
if args.subcommand == 'dump':
    print 'I will now dump "%s" in the %s format' % (args.file, args.format)
if args.subcommand == 'upload':
    print 'I will now upload "%s" to %s' % (args.file, args.server)

That looks like this on the command line:

在命令行上看起来像这样:

$ python ap.py 
usage: ap.py [-h] file {upload,dump} ...
ap.py: error: too few arguments
$ python ap.py tmp.txt 
usage: ap.py [-h] file {upload,dump} ...
ap.py: error: too few arguments
$ python ap.py tmp.txt upload
usage: ap.py file upload [-h] {amazon,imgur}
ap.py file upload: error: too few arguments
$ python ap.py tmp.txt upload amazo
usage: ap.py file upload [-h] {amazon,imgur}
ap.py file upload: error: argument server: invalid choice: 'amazo' (choose from 'amazon', 'imgur')
$ python ap.py tmp.txt upload amazon
Namespace(file='tmp.txt', server='amazon', subcommand='upload')
I will now upload "tmp.txt" to amazon
$ python ap.py tmp.txt upload imgur
Namespace(file='tmp.txt', server='imgur', subcommand='upload')
I will now upload "tmp.txt" to imgur
$ python ap.py tmp.txt dump
usage: ap.py file dump [-h] {csv,json}
ap.py file dump: error: too few arguments
$ python ap.py tmp.txt dump csv
Namespace(file='tmp.txt', format='csv', subcommand='dump')
I will now dump "tmp.txt" in the csv format
$ python ap.py tmp.txt dump json
Namespace(file='tmp.txt', format='json', subcommand='dump')
I will now dump "tmp.txt" in the json format

More info: http://docs.python.org/dev/library/argparse.html#argparse.ArgumentParser.add_subparsers

更多信息:http://docs.python.org/dev/library/argparse.html#argparse.ArgumentParser.add_subparsers

#1