An unobtrusive argparse wrapper with natural syntax
Project description
Building a command-line interface? Found yourself uttering “argh!” while struggling with the API of argparse? Don’t like the complexity but need the power?
Everything should be made as simple as possible, but no simpler.
—Albert Einstein (probably)
Argh is a smart wrapper for argparse. Argparse is a very powerful tool; Argh just makes it easy to use.
In a nutshell
Argh-powered applications are simple but flexible:
- Modular:
Declaration of commands can be decoupled from assembling and dispatching;
- Pythonic:
Commands are declared naturally, no complex API calls in most cases;
- Reusable:
Commands are plain functions, can be used directly outside of CLI context;
- Layered:
The complexity of code raises with requirements;
- Transparent:
The full power of argparse is available whenever needed;
- Namespaced:
Nested commands are a piece of cake, no messing with subparsers (though they are of course used under the hood);
- Unobtrusive:
Argh can dispatch a subset of pure-argparse code, and pure-argparse code can update and dispatch a parser assembled with Argh;
- DRY:
Don’t Repeat Yourself. The amount of boilerplate code is minimal. Among other things, Argh will:
infer command name from function name;
infer arguments from function signature;
infer argument type from the default value;
infer argument action from the default value (for booleans);
- NIH free:
Argh supports completion, progress bars and everything else by being friendly to excellent 3rd-party libraries. No need to reinvent the wheel.
Sounds good? Check the tutorial!
Relation to argparse
Argh is fully compatible with argparse. You can mix Argh-agnostic and Argh-aware code. Just keep in mind that the dispatcher does some extra work that a custom dispatcher may not do.
Installation
$ pip install argh
Examples
A very simple application with one command:
import argh
def main() -> str:
return "Hello world"
argh.dispatch_command(main)Run it:
$ ./app.py
Hello worldAn app with multiple commands:
import argh
from my_commands import hello, echo
argh.dispatch_commands([hello, echo])Run it:
$ ./app.py echo Hey
HeyA potentially modular application with more control over the process:
import argh
# declaring:
def echo(text):
"Returns given word as is."
return text
def greet(name: str, *, greeting: str = "Hello") -> str:
"Greets the user with given name. The greeting is customizable."
return f"{greeting}, {name}!"
# assembling:
parser = argh.ArghParser()
parser.add_commands([echo, greet])
# dispatching:
if __name__ == "__main__":
parser.dispatch()$ ./app.py greet Andy
Hello, Andy
$ ./app.py greet Andy -g Arrrgh
Arrrgh, AndyHere’s the auto-generated help for this application (note how the docstrings are reused):
$ ./app.py --help
usage: app.py {echo,greet} ...
positional arguments:
echo Returns given word as is.
greet Greets the user with given name. The greeting is customizable.
…and for a specific command (an ordinary function signature is converted to CLI arguments):
$ ./app.py --help greet usage: app.py greet [-g GREETING] name Greets the user with given name. The greeting is customizable. positional arguments: name optional arguments: -g GREETING, --greeting GREETING 'Hello'
(The help messages have been simplified a bit for brevity.)
Argh easily maps plain Python functions to CLI. Sometimes this is not enough; in these cases the powerful API of argparse is also available:
@arg("text", default="hello world", nargs="+", help="The message")
def echo(text: str) -> None:
print textThe approaches can be safely combined even up to this level:
# adding help to `foo` which is in the function signature:
@arg("foo", help="blah")
# these are not in the signature so they go to **kwargs:
@arg("baz")
@arg("-q", "--quux")
# the function itself:
def cmd(foo: str, bar: int = 1, *args, **kwargs) -> Iterator[str]:
yield foo
yield bar
yield ", ".join(args)
yield kwargs["baz"]
yield kwargs["quux"]Links
Project home page (GitHub)
Documentation (Read the Docs)
Package distribution (PyPI)
Questions, requests, bug reports, etc.:
Issue tracker (GitHub)
Direct e-mail (neithere at gmail com)
Support
The fastest way to improve this project is to submit tested and documented patches or detailed bug reports.
You can also donate via Liberapay. This may speed up development or simply make the original author happy :)
Licensing
Argh is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Argh is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with Argh. If not, see <http://gnu.org/licenses/>.
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