This is a program fragment of python program running on my Raspberry Pi.

gistfile1.py

---This is a program fragment.  The entire program can be seen at: https://github.com/RaspPiGuy/DS18B20TempSensor-Arduino-Pi/blob/master/Python%20Programs%20Running%20On%20The%20Pi/GraphRemoteTemperature_V1R3.py---

import serial

    
ser = serial.Serial('/dev/ttyAMA0', 115200, timeout = 5)
frame_length = 20  # One frame is all the data for one device.
global start_time

def retrieve_serial():
    """
    Called by number_of_sensors()
    First we flush anything that might be on the serial port
    We write the character "s" to the serial port.
    The Gertboard checks to see if this character is present
    If so it will write the last series of measurements to the serial port
    This function reads the data on the serial port every second
    until it finds the number of bytes to match a multiple of the
    number of bytes for each device.
    If the serial data is not found in 10 seconds, the function exits
    Returns the length of the message it has received.
    """
    ser.flushInput() # Make sure no lingering bytes on serial port
    ser.write("s")  # send "s" to trigger Gertboard to transmit data
    start_time = time.time()
    
    while time.time() - start_time < 10:
        time.sleep(1)
        recv_length = ser.inWaiting()  # finds how many bytes on serial port
        if recv_length > 0 and recv_length % frame_length == 0:
           return recv_length   # good result

    return 0  # failure
        
        
def number_of_sensors():
    """
    Called from get_stored_data() and get_measurements()
    This calls retrieve_serial()
    retrieve_serial() returns the length of the receive data
    This function calculates the number of sensors from the
    received data and populates recv_data[] with all the
    data retrieved from the Gertboard.
    Returns the number of sensors
    """
    global recv_data
    recv_data = [] # Where Gertboard data will go
    sensors = 0
    recv_length = retrieve_serial()  # will be  0 if failed

    if recv_length:
        sensors = recv_length / frame_length        
        in_coming = ser.read(size = recv_length)  # get the serial data here

        for i in range(recv_length):
            recv_data.append(ord(in_coming[i]))        

    return sensors