collectd snowball weather monitoring plugin

<Plugin python>
	ModulePath "/root/bin"
	LogTraces true
	Interactive false

	Import "sb_pressure"
	<Module sb_pressure>
		TempOffset -12.0
		PressOffset -2000.0
	</Module>
</Plugin>

sb_pressure.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Weather monitoring plugin for Snowball board

Uses onboard pressure sensor.
"""

from os import path

try:
    import collectd
except ImportError as ex:
    if __name__ != '__main__':
        raise ex

SYS_DEVICE_PATH = "/sys/bus/i2c/devices/2-005c"


def sens_enable():
    ep = path.join(SYS_DEVICE_PATH, "enable")
    with open(ep, "w") as f:
        f.write("1");


def read_pressure():
    "Get pressure in [Pa]"
    pp = path.join(SYS_DEVICE_PATH, "press_data")
    with open(pp, "r") as f:
        return float(f.readline()) * 100


def read_temperature():
    "Get temperature [C]"
    tp = path.join(SYS_DEVICE_PATH, "temp_data")
    with open(tp, "r") as f:
        return float(f.readline())


# offsets
temp_offset = 0.0
press_offset = 0.0


def config_callback(conf):
    global temp_offset, press_offset
    sens_enable()

    for c in conf.children:
        if c.key == "TempOffset":
            temp_offset = float(c.values[0])
        elif c.key == "PressOffset":
            press_offset = float(c.values[0])

    collectd.info("sb_pressure: Pressure offset: {}".format(press_offset))
    collectd.info("sb_pressure: Temperature offset: {}".format(temp_offset))


def read_callback():
    global temp_offset, press_offset

    press = read_pressure() + press_offset
    temp = read_temperature() + temp_offset

    pv = collectd.Values(plugin='sb_pressure', plugin_instance='pressure')
    pv.type = 'gauge'
    pv.values = [press]
    pv.dispatch()

    tv = collectd.Values(plugin='sb_pressure', plugin_instance='temperature')
    tv.type = 'gauge'
    tv.values = [temp]
    tv.dispatch()


if __name__ == '__main__':
    sens_enable()
    print "Current air pressure: {} Pa, temperature: {} C°".format(
        read_pressure(),
        read_temperature()
    )
else:
    collectd.register_config(config_callback)
    collectd.register_read(read_callback)