i3 status extension script which adds fan and governor info

i3status.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This script is a simple wrapper which prefixes each i3status line with custom
# information. It is a python reimplementation of:
# http://code.stapelberg.de/git/i3status/tree/contrib/wrapper.pl
#
# To use it, ensure your ~/.i3status.conf contains this line:
#     output_format = "i3bar"
# in the 'general' section.
# Then, in your ~/.i3/config, use:
#     status_command i3status | ~/i3status/contrib/wrapper.py
# In the 'bar' section.
#
# In its current version it will display the cpu frequency governor, but you
# are free to change it to display whatever you like, see the comment in the
# source code below.
#
# © 2012 Valentin Haenel <valentin.haenel@gmx.de>
#
# This program is free software. It comes without any warranty, to the extent
# permitted by applicable law. You can redistribute it and/or modify it under
# the terms of the Do What The Fuck You Want To Public License (WTFPL), Version
# 2, as published by Sam Hocevar. See http://sam.zoy.org/wtfpl/COPYING for more
# details.

import sys
import json

def get_fan():
    """Get the current fan speed."""
    with open('/proc/acpi/ibm/fan') as fp:
        speed = 0
        for line in fp:
            line = line.strip()
            if line.startswith('speed:'):
                speed = line.split('\t')[-1]
            elif line.startswith('level:'):
                return speed, line.split('\t')[-1]


def get_governor():
    """ Get the current governor for cpu0, assuming all CPUs use the same. """
    with open('/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor') as fp:
        return fp.readlines()[0].strip()

def print_line(message):
    """ Non-buffered printing to stdout. """
    sys.stdout.write(message + '\n')
    sys.stdout.flush()

def read_line():
    """ Interrupted respecting reader for stdin. """
    # try reading a line, removing any extra whitespace
    try:
        line = sys.stdin.readline().strip()
        # i3status sends EOF, or an empty line
        if not line:
            sys.exit(3)
        return line
    # exit on ctrl-c
    except KeyboardInterrupt:
        sys.exit()

if __name__ == '__main__':
    # Skip the first line which contains the version header.
    print_line(read_line())

    # The second line contains the start of the infinite array.
    print_line(read_line())

    while True:
        line, prefix = read_line(), ''
        # ignore comma at start of lines
        if line.startswith(','):
            line, prefix = line[1:], ','

        j = json.loads(line)
        # insert information into the start of the json, but could be anywhere
        # CHANGE THIS LINE TO INSERT SOMETHING ELSE
        speed, level = get_fan()
        j.insert(5, {'full_text' : '%s' % level, 'name' : 'level'})
        j.insert(6, {'full_text' : '%s' % speed, 'name' : 'fan'})
        j.insert(7, {'full_text' : '%s' % get_governor(), 'name' : 'gov'})
        # and echo back new encoded json
        print_line(prefix+json.dumps(j))