range lib. MaxBotix.com/@zmatt

import serial
import re

class Range(serial.Serial):
    def __init__(self, port):
        super().__init__(port=port, baudrate=9600, timeout=1)

    def measure( self ):
        self.reset_input_buffer()

        data = self.read_until(b'\r', size=5)

        if re.fullmatch(rb'\d*\r', data):
            # partial line received, wait for next one
            data = self.read_until(b'\r', size=5)

        if len(data) < 5 and not data.endswith(b'\r'):
            raise RuntimeError("Timeout while waiting for data")

        m = re.fullmatch(rb'R(\d+)\r', data)
        if not m:
            raise RuntimeError("Garbage data received: %r" % data)
        data = m.group(1)

        return int(data)  # measurement in inches (0-255)