Create CLIs with classes and type hints.
Project description
Cliar
Cliar is yet another Python package to create commandline interfaces. It focuses on simplicity, extensibility, and testability:
- Creating a CLI is as simple as creating subclassing
cliar.Cliar
. - Extending a CLI is as simple as subclassing from the base CLI class.
- Testing a CLI is as simple as unittesting a class.
Cliar's mission is to let the programmer focus on the business logic instead of building an interface for it. At the same time, Cliar doesn't want to stand in the programmer's way, so it provides means to customize the generated CLI.
Installation
pip install cliar
Cliar runs with Python 3.6+ on Windows, Linux, and Mac. There are no dependencies outside Python's standard library.
Basic Usage
Let's create a calculator app. Version 1.0.0 will implement only addition of two real numbers.
Here's how you do it with Cliar:
from cliar import Cliar
class Calculator(Cliar):
'''Calculator app.'''
def add(self, x: float, y: float):
'''Add two real numbers.'''
print(f'The sum of {x} and {y} is {x+y}.')
if __name__ == '__main__':
Calculator().parse()
Save this code as calc.py
and run it with different inputs:
$ python run calc.py add 12 34
The sum of 12.0 and 34.0 is 46.0.
$ python run calc.py foo bar
usage: calc.py add [-h] x y
calc.py add: error: argument x: invalid float value: 'foo'
$ python run calc.py -h
usage: calc.py [-h] {add} ...
Calculator app.
optional arguments:
-h, --help show this help message and exit
commands:
{add} Available commands:
add Add two real numbers.
$ python calc.py add -h
usage: calc.py add [-h] x y
Add two real numbers.
positional arguments:
x
y
optional arguments:
-h, --help show this help message and exit
There are a few things to note in the code above:
- It's a regular Python class with a regular Python method. You don't need to learn any new syntax to use Cliar.
- The
add
method was converted intoadd
command, and its positional params were converted into positional commandline args. - We don't convert
x
ory
tofloat
or handle any potential conversion errors in theadd
body. Instead, we treatx
andy
as if they were already guaranteed to be floats. That's because Cliar does the validation and conversion for us, using the information fromadd
's type hints. Note how invalid input doesn't even reach your code. - The
--help
and-h
flags are added automatically and the help messages were generated from the docstrings.
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