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</head>
Argh: The Natural CLI
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);
|
|---|
| Term-Friendly: | Command output is processed with respect to stream encoding;
|
|---|
| Unobtrusive: | Argh can dispatch a subset of pure-argparse code, and pure-argparse
code can update and dispatch a parser assembled with Argh;
|
|---|
| DRY: | 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);
- add an alias root command help for the --help argument.
|
|---|
| 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
Using pip:
$ pip install argh
Arch Linux (AUR):
$ yaourt python-argh
Examples
A very simple application with one command:
System Message: WARNING/2 (<stdin>, line 113)
Cannot analyze code. Pygments package not found.
.. code-block:: python
import argh
def main():
return 'Hello world'
argh.dispatch_command(main)
Run it:
System Message: WARNING/2 (<stdin>, line 124)
Cannot analyze code. Pygments package not found.
.. code-block:: bash
$ ./app.py
Hello world
A potentially modular application with multiple commands:
System Message: WARNING/2 (<stdin>, line 131)
Cannot analyze code. Pygments package not found.
.. code-block:: python
import argh
# declaring:
def echo(text):
"Returns given word as is."
return text
def greet(name, greeting='Hello'):
"Greets the user with given name. The greeting is customizable."
return greeting + ', ' + name
# assembling:
parser = argh.ArghParser()
parser.add_commands([echo, greet])
# dispatching:
if __name__ == '__main__':
parser.dispatch()
Of course it works:
System Message: WARNING/2 (<stdin>, line 157)
Cannot analyze code. Pygments package not found.
.. code-block:: bash
$ ./app.py greet Andy
Hello, Andy
$ ./app.py greet Andy -g Arrrgh
Arrrgh, Andy
Here'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:
System Message: WARNING/2 (<stdin>, line 196)
Cannot analyze code. Pygments package not found.
.. code-block:: python
@arg('text', default='hello world', nargs='+', help='The message')
def echo(text):
print text
The approaches can be safely combined even up to this level:
System Message: WARNING/2 (<stdin>, line 204)
Cannot analyze code. Pygments package not found.
.. code-block:: python
# 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, bar=1, *args, **kwargs):
yield foo
yield bar
yield ', '.join(args)
yield kwargs['baz']
yield kwargs['quux']
Author
Developed by Andrey Mikhaylenko since 2010.
See file AUTHORS for a complete list of contributors to this library.
Support
The fastest way to improve this project is to submit tested and documented
patches or detailed bug reports.
Otherwise you can "flattr" me: 
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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