Python script that runs a webservice that returns readings from DS18B20 temperature sensors connected to a Raspberry Pi as JSON data for al sensors or a specific sensor

temps.py

#!/usr/bin/env python

# You will need to have web.py installed. To install, run: pip install web.py

# How to install as service: http://blog.scphillips.com/posts/2013/07/getting-a-python-script-to-run-in-the-background-as-a-service-on-boot/
# Should the above page be offline; a mirror is at: http://archive.is/20160529210455/http://blog.scphillips.com/posts/2013/07/getting-a-python-script-to-run-in-the-background-as-a-service-on-boot/

# You can run this as:
#     python temps.py
# This will run the service on port 8080; # Optionally, you can specify a port:
#     python temps.py 1234

# When running you can query http://localhost:8080/sensors for all sensor temperature readings or
# http://localhost:8080/sensor/<sensor-id> (e.g. http://localhost:8080/sensor/28-041600ffb5ff) for
# the temperature reading of that specific sensor.

import sys
import web
import json
import os
from threading import Thread

urls = (
    '/sensors', 'sensors',
    '/sensor/(.+)', 'sensor'
)

class sensors:

    def GET(self):
        temps = {}

        # We read every sensor in it's own thread; this speeds up the process massively
        # The DS18B20 driver sets the IC in 'read mode', then waits ~750ms, then reads the value; if we do this
        # concurrently we don't have to wait num_sensors x sensor_delay but only 1 x sensor_delay (+ slight overhead)
        # For 4 sensors we go from 3.5~4.0 seconds to 0.8~1.0 seconds
        threads = []
        sensors = SensorReader.ListSensors()
        for s in sensors:
            process = Thread(target=self.Retrieve, args=[s, temps])
            process.start()
            threads.append(process)

        for process in threads:
            process.join()

        return json.dumps(temps);                   # Return data as json

    def Retrieve(self, sensor, result):
        result.update(SensorReader.Read(sensor))

class sensor:

    def GET(self, id):
        return json.dumps(SensorReader.Read(id));   # Return data as json

class SensorReader:
    SENSORROOT = '/sys/bus/w1/devices/'

    @staticmethod
    def ListSensors():
        return open(SensorReader.SENSORROOT + 'w1_bus_master1/w1_master_slaves').read().splitlines()   # Find all sensors;

    @staticmethod
    def Read(id):
        fname = SensorReader.SENSORROOT + id +"/w1_slave"
        if os.path.isfile(fname):                   # Sensor id exists?
            with open(fname, "r") as f:
                data = f.readlines()

            if data[0].strip()[-3:] == "YES":       # Make sure sensor is ready & OK
                return { id: float(data[1].split("=")[1]) / 1000 }

        return { id: None }                         # Return null when not found or error


if __name__ == "__main__":
    app = web.application(urls, globals())
    app.internalerror = web.debugerror
    app.run()