Reading Serial Data with Python

I am trying to read a line of serial data from a MaxBotix sonar sensor with Python. The sensor spits out R0300 The integers after the "R" are the distance read in millimeters. I am trying to write a script that removes the "R" and converts the string into an integer. I successfully removed the "R" but when I try to convert the string into an int I get this error: ValueError: invalid literal for int() with base 10: '1187\r1187\r1188\r1188\r1188\r1188\r1188\r1188\r1188\r1188\r1188\r1189\r1189\r1189\r1189\r1189\r118'

I'm new to Python, here is the code:

import serial
from time import sleep

mmtoinch = 25.4

#print ser.isOpen() #to check port is open
ser = serial.Serial('/dev/ttyAMA0', 9600)
try:
   while True:
      rawdata = ser.readline(100)
      #Removing the "R" from the Range Finder output
      intconversion = rawdata.replace("R","")
      #print(rawdata)
      intconversion.replace(" ","")
      print(intconversion)
      intrange = int(intconversion)
      sleep(1)

except KeyboardInterrupt:
     print ' end'

Indentation may be wrong. Any help is greatly appreciated! Thank you in advance :)