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:
- Pythonic, KISS:
Commands are plain Python functions. Almost no CLI-specific API to learn.
- Reusable:
Endpoint functions can be used directly outside of CLI context.
- Static typing friendly:
100% of the code including endpoint functions can be type-checked. Argh is driven primarily by type annotations.
- 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 types, actions and much more from annotations.
- Modular:
Declaration of commands can be decoupled from assembling and dispatching.
- Layered:
The complexity of code raises with requirements.
- Transparent:
You can directly access argparse.ArgumentParser if needed.
- Subcommands:
Easily nested commands. Argh isolates the complexity of subparsers.
- NIH free:
Argh supports completion, progress bars and everything else by being friendly to excellent 3rd-party libraries. No need to reinvent the wheel.
- Compact:
No dependencies apart from Python’s standard library.
Sounds good? Dive in! :)
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
Hello World
A very simple application with one command:
import argh
def main() -> str:
return "Hello world"
argh.dispatch_command(main)Run it:
$ ./app.py
Hello worldType Annotations
Type annotations are used to infer argument types:
def summarise(numbers: list[int]) -> int:
return sum(numbers)
argh.dispatch_command(summarise)Run it (note that nargs="+" + type=int were inferred from the annotation):
$ ./app.py 1 2 3
6Multiple Commands
An app with multiple commands:
import argh
from my_commands import hello, echo
argh.dispatch_commands([hello, echo])Run it:
$ ./app.py echo Hey
HeyModularity
A 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.)
Decorators
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("words", default="hello world", nargs="+", help="The message")
def echo(words: list[str]) -> str:
return " ".join(words)Please note that decorators will soon be fully replaced with annotations.
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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