Conditional command line arguments in Python using argparse
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.
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.')
解决这个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
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".
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:
$ 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
链接地址: http://www.djcxy.com/p/61966.html上一篇: 作为选项传递列表的argparse选项