argparse-使用特定参数重现“ --help”参数的行为

Question

I have some trouble while working with the argparse module for Python v2.7. Basically, what I have is a script that works with 5 mandatory arguments :

1. url
2. method
3. login
4. password
5. output

An example of the syntax would look like this :

script.py -w/--url [URL] -m/--method [METHOD] -l/--login [LOGIN] -p/--password [PASSWORD] -o/--output [OUTPUT]

What I'd like to do is this :

• add an optional argument -t/--test
• its behavior would be that, based on the url used with the -w/--url argument, it would bypass completely the -m/--method , -l/--login and -p/--password arguments but, for it to work, I need to tell argparse to stop processing arguments if -t/--test is provided (but only with -w/--url ).

Is this behavior even possible? I tried to play with argparse sub-commands but it seems to be (at least to my small knowledge) a bit overkill.

NB: Here is my original code :

# Description : parses script arguments
# Argument(s) : all
# Return value : all arguments values
def testArgs():
    parser = argparse.ArgumentParser(description='Foo', formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument('-w','--url', help='URL', required=True)
    parser.add_argument('-t','--test', help='Test command', action='store_true')
    parser.add_argument('-m','--method', help='METHOD', required=True)
    parser.add_argument('-u','--login_name', help='LOGIN', required=True)
    parser.add_argument('-p','--login_password', help='PASSWORD', required=True)
    parser.add_argument('-o','--output_format', help='OUTPUT', required=True, choices=['json', 'yaml', 'python'], default='json')
    args = parser.parse_args()
    return args

EDIT : After a lot of testing, I have managed the following :

def testArgs():
    parser = argparse.ArgumentParser(description='DESCRIPTION')
    subparsers = parser.add_subparsers()
    p_list = subparsers.add_parser('test', help='List all available methods')
    p_list.add_argument('-w', help='URL', required=True)
    p_list.add_argument('-t', help='Test', action='store_true', required=True)
    p_cmd = subparsers.add_parser('cmd', help='Executes command')
    p_cmd.add_argument('-w', help='URL', required=True)
    p_cmd.add_argument('-m', help='Method', required=True)
    p_cmd.add_argument('-l', help='Login', required=True)
    p_cmd.add_argument('-p', help='Password', required=True)
    p_cmd.add_argument('-o', help='Output', required=True)
    args = parser.parse_args()
    return args

Which exhibits the following behavior :

$ python testArgparse.py -h
usage: testArgeparse.py [-h] {test,cmd} ...

DESCRIPTION

positional arguments:
  {test,cmd}
    test      Lists all available methods
    cmd       Executes command

optional arguments:
  -h, --help  show this help message and exit

But to access help on the others arguments, I need to do the following :

$ python testArgparse.py test -h
usage: testArgparse.py test [-h] -w W -t

optional arguments:
  -h, --help  show this help message and exit
  -w W        URL
  -t          Test


$ python testArgparse.py cmd -h
usage: testArgparse.py cmd [-h] -w W -m M -l L -p P -o O

optional arguments:
  -h, --help  show this help message and exit
  -w W        URL
  -m M        Method
  -l L        Login
  -p P        Password
  -o O        Output

I'd like to be able to, at least, display help about all arguments without having to use --help for both test and cmd arguments.

Ideally, what I'd like is this behavior :

$ python testArgparse.py [-w URL -t] | [-w URL -m METHOD -u LOGIN -p PASS -o OUTPUT]

Answer 1

required=True with store_true does not make sense. The default is False , but if it is required the returned value will always be True .

Since only -w is required unconditionally, I would drop the required parameter on everything else. Then test for the required values after parse_args . I can still issue an argparse error with usage at that time. In other words, do my own testing rather than try something fancy in argparse.

def testArgs():
    usage = '[-w URL -t] | [-w URL -m METHOD -u LOGIN -p PASS -o OUTPUT]'
    parser = argparse.ArgumentParser(description='DESCRIPTION',usage=usage)
    parser.add_argument('-w', help='URL', required=True)
    parser.add_argument('-t', help='Test', action='store_true')
    parser.add_argument('-m', help='Method')
    parser.add_argument('-l', help='Login')
    parser.add_argument('-p', help='Password')
    parser.add_argument('-o', help='Output')
    args = parser.parse_args()

    # sample test, streamline and refine to suit your needs
    # this assumes the default for all these args is None
    if not args.t: # '-t' in in argv
        if any([args.m is None, args.l is None, args.p is None, args.o is None]):
            parser.error('m,l,p,o are all required')
    return args

1216:~/mypy$ python2.7 stack21070971.py
usage: [-w URL -t] | [-w URL -m METHOD -u LOGIN -p PASS -o OUTPUT]
stack21070971.py: error: argument -w is required

1213:~/mypy$ python2.7 stack21070971.py -w url
usage: [-w URL -t] | [-w URL -m METHOD -u LOGIN -p PASS -o OUTPUT]
stack21070971.py: error: m,l,p,o are all required

1213:~/mypy$ python2.7 stack21070971.py -w url -t
Namespace(l=None, m=None, o=None, p=None, t=True, w='url')

1214:~/mypy$ python2.7 stack21070971.py -w url -m mmm
usage: [-w URL -t] | [-w URL -m METHOD -u LOGIN -p PASS -o OUTPUT]
stack21070971.py: error: m,l,p,o are all required
...

1215:~/mypy$ python2.7 stack21070971.py -w url -m mmm -l uuu -p ppp -o ooo
Namespace(l='uuu', m='mmm', o='ooo', p='ppp', t=False, w='url')