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

Question

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','\r\n']

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 and Padraic who provided Answers, I can confirm an update on how to fix the above problem. I prefer Padraic's solution, slightly more elegant, but either work. I added the following:

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

sInput = oSer.readline().strip() #but see answers below from Pad for more detail

Answer 1

The error is caused by the \\r\\n at the end of the line. int() and float() don't like that.

You can either strip it off like so:

sInput = oSer.readline().strip()

Or you can modify the loop to ignore non-numbers:

liInput = [int(i) for i in lsInput if i.isdigit()]

Answer 2

You can rstrip the trailing white space:

while True:
    sInput = oSer.readline().rstrip().split(",")

Or a more robust approach is to see if an element can be cast to a float using a try/except:

def cast(it):
    for ele in it:
        try:
            yield float(ele)
        except ValueError:
            pass


while True:
    sInput = oSer.readline().rstrip(",\r\n").split(",")
    nums = list(cast(sInput.split(",")))

cast will work for floats, ints and negative numbers.