pub.py
import paho.mqtt.client as mqtt
from time import sleep
import serial
ser = serial.Serial('/dev/ttyACM0', 9600, timeout=1)

if __name__ == '__main__':

###
### 以下、Sango のアカウント情報の定義
###
    username = Sango のユーザ名
    password = Sango のパスワード
    host = 'free.mqtt.shiguredo.jp'
    topic = 'Sango のユーザ名/test_topic'
###
###
###
    port = 1883

    client = mqtt.Client()
    client.username_pw_set(username, password=password)
    client.connect(host, port=port, keepalive=60)

    while 1:
        # value = random.random() * 100
        ser.write('a'); # シリアルへの書き出しコマンド
        sleep(0.05)
        value = ser.readline()
        print '[{}] Sending message to sango.'.format(value)
        client.publish(topic, '{}'.format(value))
        ser.readline() # もしさらに値があれば読み捨て
        sleep(0.5)