Python readline() returns string that wont convert to int or float

I am using Arduino SoftwareSerial library to send serial data to a Raspberry Rx pin. I can get the Arduino serial data sent over to the Raspberry successfully, in as much that the integers I sent arrive as the equivalent in a string.

The problem:

I am trying to convert the string that the .readline() returns into a float or int, but I am unable to do so.

import serial
oSer = serial.Serial("/dev/ttyAMA0",baudrate=57600,timeout=1)

while True:
    sInput = oSer.readline()
    print sInput #Returns: >>1,2,3,

    lsInput = sInput.split(',')
    print lsInput #Returns: >>['1','2','3','rn']

How can I convert this to an int or float? I simply need to do some arithmetic with the numbers. I have tried:

    lfInput = [float(i) for i in lsInput] #Returns: >> ValueError: could not convert to float:

    liInput = [int(i) for i in lsInput] #Returns: >> ValueError: invalid literal for int() with base 10: ''

The Answer

Thanks to John/Padraic and Oscar who provided Answers I can give an update on how to fix the above problem. I prefer Johsn solution, slightly more elegant, but either work. I added the following:

John's/Pad solution (see answers below for better and more detail):

sInput = oSer.readline().strip()

Oscars solution:

if (len(lsInput) > 3): # this is to help with the first line of serial input which is often full of errors
    (a,b,c,d) = lsInput # as shown above the serial communication returns a funny last term, my guess it has something to do with the println on the arduino side
    aint = int(a) # is now possible