Re: argparse — adding a --version flag in the face of positional args
On Tue, 29 Nov 2022 at 12:37, Loris Bennett wrote: > > Mats Wichmann writes: > > > On 11/27/22 16:40, Skip Montanaro wrote: > >> I have a script to which I'd like to add a --version flag. It should print > >> the version number then exit, much in the same way --help prints the help > >> text then exits. I haven't been able to figure that out. I always get a > >> complaint about the required positional argument. > >> I think I could use something like nargs='*', but that would push > >> off > >> detection of the presence of the positional arg to the application. > >> Shouldn't I be able to tell argparse I'm going to process --verbose, then > >> exit? > > > > ummm, hate to say this, but have you checked the documentation? this > > case is supported using an action named 'version' without doing very > > much. > > I hadn't noticed the action 'version'. I just use > > parser.add_argument( > "-v", "--version", action="store_true", dest="version", > help="print version" > ) > That's still going to validate the rest of the args though - notably, you can't omit any mandatory arguments (like a subcommand). The version and help actions are implemented pretty simply, actually. They're just little action classes that do their action immediately on getting triggered. It should be easy enough to make any action you want that way. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: argparse — adding a --version flag in the face of positional args
On Sun, 27 Nov 2022 22:23:16 -0600, Karen Park declaimed the following: >I figured it out…there was a logistics file given with the assignment! I >thought it was supposed to be a download included with the python >download…oops! > I think you made this response in the wrong thread... -- Wulfraed Dennis Lee Bieber AF6VN wlfr...@ix.netcom.comhttp://wlfraed.microdiversity.freeddns.org/ -- https://mail.python.org/mailman/listinfo/python-list
Re: argparse — adding a --version flag in the face of positional args
Mats Wichmann writes:
> On 11/27/22 16:40, Skip Montanaro wrote:
>> I have a script to which I'd like to add a --version flag. It should print
>> the version number then exit, much in the same way --help prints the help
>> text then exits. I haven't been able to figure that out. I always get a
>> complaint about the required positional argument.
>> I think I could use something like nargs='*', but that would push
>> off
>> detection of the presence of the positional arg to the application.
>> Shouldn't I be able to tell argparse I'm going to process --verbose, then
>> exit?
>
> ummm, hate to say this, but have you checked the documentation? this
> case is supported using an action named 'version' without doing very
> much.
I hadn't noticed the action 'version'. I just use
parser.add_argument(
"-v", "--version", action="store_true", dest="version",
help="print version"
)
...
if args.version:
print(f"Version {my_module.__version__}")
sys.exit(0)
where the version is specified in a pyproj.toml file and __init__.py
contains
try:
import importlib.metadata as importlib_metadata
except ModuleNotFoundError:
import importlib_metadata
__version__ = importlib_metadata.version(__name__)
I use poetry to then build the corresponding versioned package.
What am I missing by not using the action 'version'? Do I just save
having to explicitly test for the version arg?
Cheers,
Loris
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Re: argparse — adding a --version flag in the face of positional args
Thanks. It occurs to me that instead of providing two special actions
("help" and "version"), it might be worthwhile to provide a standard way of
saying, "if present, process this option and exit before considering other
details of the command line." Matt's example action works well enough for
my needs, but it would be nice if more than one such option could be given.
For example:
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("url")
parser.add_argument("--version", version="777", action="version")
args = parser.parse_args(["--help", "--version"])
Which option is processed depends on their order on the command line. I
don't believe it's possible to run the script and see them both processed.
That's probably a secondary consideration though. My script is working well
enough in this regard now.
Skip
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Re: argparse — adding a --version flag in the face of positional args
More better:
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("positional",type=int)
parser.add_argument('--version',action="version",version="2.0")
args = parser.parse_args()
# double argument
print(args.positional * 2)
From: Python-list on
behalf of Weatherby,Gerard
Date: Sunday, November 27, 2022 at 10:29 PM
To: Skip Montanaro , Python
Subject: Re: argparse — adding a --version flag in the face of positional args
Use two parsers:
import argparse
import sys
vparser = argparse.ArgumentParser(add_help=False)
vparser.add_argument('--version',action="store_true",help="show version")
# look for version, ignore remaining arguments
vargs, _ = vparser.parse_known_args()
if vargs.version:
print("Version 2.0")
sys.exit(0)
parser = argparse.ArgumentParser()
parser.add_argument("positional",type=int)
# add version again, so it displays if --help called
parser.add_argument('--version',action="store_true",help="show version")
args = parser.parse_args()
# double argument
print(args.positional * 2)
From: Python-list on
behalf of Skip Montanaro
Date: Sunday, November 27, 2022 at 6:42 PM
To: Python
Subject: argparse — adding a --version flag in the face of positional args
*** Attention: This is an external email. Use caution responding, opening
attachments or clicking on links. ***
I have a script to which I'd like to add a --version flag. It should print
the version number then exit, much in the same way --help prints the help
text then exits. I haven't been able to figure that out. I always get a
complaint about the required positional argument.
I think I could use something like nargs='*', but that would push off
detection of the presence of the positional arg to the application.
Shouldn't I be able to tell argparse I'm going to process --verbose, then
exit?
Thx,
Skip
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Re: argparse — adding a --version flag in the face of positional args
I figured it out…there was a logistics file given with the assignment! I thought it was supposed to be a download included with the python download…oops! Thanks, Karen > On Nov 27, 2022, at 9:34 PM, Skip Montanaro wrote: > > >> >> >> ummm, hate to say this, but have you checked the documentation? this >> case is supported using an action named 'version' without doing very much. >> > > Thanks, Mats. > > I actually searched all over the argparse docs. (There's a lot to digest. > Honestly, if I wasn't attempting to be sort of up-to-date I'd just continue > using getopt.) It never occurred to me that "version" would be special, so > I didn't specifically search for it, or realize there would be a specific > action devoted to it. I knew (the default) "help" was special, so I focused > my search for it. Obviously, "--help" is a pretty bad search term. > > Skip > >> > -- > https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
Re: argparse — adding a --version flag in the face of positional args
> > ummm, hate to say this, but have you checked the documentation? this > case is supported using an action named 'version' without doing very much. > Thanks, Mats. I actually searched all over the argparse docs. (There's a lot to digest. Honestly, if I wasn't attempting to be sort of up-to-date I'd just continue using getopt.) It never occurred to me that "version" would be special, so I didn't specifically search for it, or realize there would be a specific action devoted to it. I knew (the default) "help" was special, so I focused my search for it. Obviously, "--help" is a pretty bad search term. Skip > -- https://mail.python.org/mailman/listinfo/python-list
Re: argparse — adding a --version flag in the face of positional args
Use two parsers:
import argparse
import sys
vparser = argparse.ArgumentParser(add_help=False)
vparser.add_argument('--version',action="store_true",help="show version")
# look for version, ignore remaining arguments
vargs, _ = vparser.parse_known_args()
if vargs.version:
print("Version 2.0")
sys.exit(0)
parser = argparse.ArgumentParser()
parser.add_argument("positional",type=int)
# add version again, so it displays if --help called
parser.add_argument('--version',action="store_true",help="show version")
args = parser.parse_args()
# double argument
print(args.positional * 2)
From: Python-list on
behalf of Skip Montanaro
Date: Sunday, November 27, 2022 at 6:42 PM
To: Python
Subject: argparse — adding a --version flag in the face of positional args
*** Attention: This is an external email. Use caution responding, opening
attachments or clicking on links. ***
I have a script to which I'd like to add a --version flag. It should print
the version number then exit, much in the same way --help prints the help
text then exits. I haven't been able to figure that out. I always get a
complaint about the required positional argument.
I think I could use something like nargs='*', but that would push off
detection of the presence of the positional arg to the application.
Shouldn't I be able to tell argparse I'm going to process --verbose, then
exit?
Thx,
Skip
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Re: argparse — adding a --version flag in the face of positional args
On 11/27/22 16:40, Skip Montanaro wrote: I have a script to which I'd like to add a --version flag. It should print the version number then exit, much in the same way --help prints the help text then exits. I haven't been able to figure that out. I always get a complaint about the required positional argument. I think I could use something like nargs='*', but that would push off detection of the presence of the positional arg to the application. Shouldn't I be able to tell argparse I'm going to process --verbose, then exit? ummm, hate to say this, but have you checked the documentation? this case is supported using an action named 'version' without doing very much. -- https://mail.python.org/mailman/listinfo/python-list
Re: argparse — adding a --version flag in the face of positional args
> class VersionAction(argparse.Action):
> def __call__(self, parser, namespace, values, option_string):
> print(VERSION)
> exit()
...
> parser.add_argument("-v", "--version", nargs=0, action=VersionAction)
Thanks. An action class didn't occur to me. I looked briefly at the
code for argparse to see how it handled --help. The added argument
seemed normal, so gave up, figuring there was some special handling of
that option.
Skip
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Re: argparse — adding a --version flag in the face of positional args
I wondered whether subparsers might work, but they don't quite fit here.
This seems to fit the bill fairly well, though I agree it would be
nice if there were a neater option:
import argparse
import sys
VERSION = 0.1
def main(args):
parser.parse_args(args)
class VersionAction(argparse.Action):
def __call__(self, parser, namespace, values, option_string):
print(VERSION)
exit()
parser = argparse.ArgumentParser()
parser.add_argument("-v", "--version", nargs=0, action=VersionAction)
parser.add_argument("pos", nargs=1)
if __name__ == "__main__":
main(sys.argv[1:])
On Sun, 27 Nov 2022 at 23:40, Skip Montanaro wrote:
>
> I have a script to which I'd like to add a --version flag. It should print
> the version number then exit, much in the same way --help prints the help
> text then exits. I haven't been able to figure that out. I always get a
> complaint about the required positional argument.
>
> I think I could use something like nargs='*', but that would push off
> detection of the presence of the positional arg to the application.
> Shouldn't I be able to tell argparse I'm going to process --verbose, then
> exit?
>
> Thx,
>
> Skip
> --
> https://mail.python.org/mailman/listinfo/python-list
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argparse — adding a --version flag in the face of positional args
I have a script to which I'd like to add a --version flag. It should print the version number then exit, much in the same way --help prints the help text then exits. I haven't been able to figure that out. I always get a complaint about the required positional argument. I think I could use something like nargs='*', but that would push off detection of the presence of the positional arg to the application. Shouldn't I be able to tell argparse I'm going to process --verbose, then exit? Thx, Skip -- https://mail.python.org/mailman/listinfo/python-list
