GPIO Zero YAML/JSON config parser

gpiozero_config_parser.py

import gpiozero
from signal import pause
import json
try:
    import yaml
except ImportError:
    yaml = None

classes = {
    name: cls
    for name, cls in gpiozero.__dict__.items()
    if isinstance(cls, type) and issubclass(cls, gpiozero.Device)
}

class GPIOZeroConfigParser:
    def __init__(self, config_file):
        ext = config_file.split('.')[-1]
        _format = {
            'json': json,
            'yml': yaml
        }[ext]
        with open(config_file, 'r') as f:
            self.config = _format.load(f)

        self.devices = {}
        self.device_data = {}
        self.classes = set()
        for device in self.config['devices']:
            for obj_name, data in device.items():
                class_name, *args = data.split(', ')
                ClassName = classes[class_name]
                self.classes.add(ClassName)
                self.devices[obj_name] = ClassName(*[int(arg) for arg in args])
                self.device_data[obj_name] = {
                    'class_name': class_name,
                    'args': [int(arg) for arg in args]
}

        for connection in self.config['connections']:
            for source_device_ref, value_device_ref in connection.items():
                source_device = self.devices[source_device_ref]
                value_device = self.devices[value_device_ref]
                source_device.source = value_device.values

    def to_python(self):
        classes = ', '.join(obj.__name__ for obj in self.classes)
        devices = '\n'.join(
            '{} = {}({})'.format(obj_name, data['class_name'], *data['args'])
            for obj_name, data in self.device_data.items()
        )
        connections = '\n'.join(
            '{}.source = {}.values'.format(source_device, value_device)
            for connection in self.config['connections']
            for source_device, value_device in connection.items()
        )

        return """from gpiozero import {}
from signal import pause

{}

{}

pause()""".format(classes, devices, connections)

led_button.json

{
    "devices": [
        {"led": "LED, 17"},
        {"btn": "Button, 18"}
    ],
    "connections": [
        {"led": "btn"}
    ]
}

led_button.yml

devices:
    - led: LED, 17
    - btn: Button, 18
connections:
    - led: btn