read_serial_json.py

import json
import serial


# this port address is for the serial tx/rx pins on the GPIO header
SERIAL_PORT = '/dev/ttyAMA0'
# be sure to set this to the same rate used on the Arduino
SERIAL_RATE = 9600


def main():
    ser = serial.Serial(SERIAL_PORT, SERIAL_RATE)
    while True:
        # using ser.readline() assumes each line contains a single reading
        # sent using Serial.println() on the Arduino
        reading = ser.readline().decode('utf-8')
        # reading is a string...and if it's JSON formatted...
        data = json.loads(reading)
        # data will be a list or a dictionary depending on whether 
        # the 'reading' string was a JSON array or object
        print(data)

if __name__ == "__main__":
    main()