platypush/platypush/backend/sensor/__init__.py

from platypush.backend import Backend
from platypush.message.event.sensor import SensorDataChangeEvent, \
    SensorDataAboveThresholdEvent, SensorDataBelowThresholdEvent


class SensorBackend(Backend):
    def __init__(self, thresholds=None, *args, **kwargs):
        """
        Thresholds is either a scalr value or a dictionary.

        If set, SensorDataAboveThresholdEvent and SensorDataBelowThresholdEvent
        events will be triggered whenever the measurement goes above or below
        that value.

        Set it as a scalar if your get_measurement() code returns a scalar,
        as a dictionary if it returns a dictionary of values.

        For instance, if your sensor code returns both humidity and temperature
        in a format like {'humidity':60.0, 'temperature': 25.0}, you'll want to
        set up a threshold on temperature with a syntax like {'temperature':20.0}
        """

        super().__init__(**kwargs)
        self.measurement = None
        self.thresholds = thresholds

    def get_measurement(self):
        raise NotImplementedError('To be implemented in a derived class')

    def run(self):
        super().run()

        while not self.should_stop():
            new_data = self.get_measurement()
            if self.data is None or self.data != new_data:
                self.bus.post(SensorDataChangeEvent(data=new_data))

            if self.thresholds:
                if isinstance(self.thresholds, dict) and isinstance(new_data, dict):
                    for (measure, threshold) in self.thresholds.items():
                        if measure not in new_data:
                            continue

                        if new_data[measure] > threshold and (self.data is None or (
                                measure in self.data and self.data[measure] <= threshold)):
                            self.bus.post(SensorDataAboveThresholdEvent(data=new_data))
                        elif new_data[measure] < threshold and (self.data is None or (
                                measure in self.data and self.data[measure] >= threshold)):
                            self.bus.post(SensorDataBelowThresholdEvent(data=new_data))
                else:
                    if new_data > threshold and (self.data is None or self.data <= threshold):
                        self.bus.post(SensorDataAboveThresholdEvent(data=new_data))
                    elif new_data < threshold and (self.data is None or self.data >= threshold):
                        self.bus.post(SensorDataBelowThresholdEvent(data=new_data))

            self.data = new_data


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