Im having an issue using PySerial while communicating with my Arduino - arduino

Question

So I'm trying to make a lighting system for my computer, I wanted to write the GUI and whatnot within Python and handle all the controlling of lights and stuff with the Arduino. After some research PySerial seemed like the easiest to use and understand being a beginner myself. I honestly have no idea what I'm doing here and I'm getting errors that I can't diagnose, and Google is not helping whatsoever.
Here is the code I have running in python now:
import serial
ser = serial.Serial('COM8', 9600) # Establish the connection on a specific port
while True:
numIn = str(input("Enter a Color value: "))
ser.write(numIn)
print (ser.readline())
On the Arduino side I have:
void setup ()
{
Serial.begin (9600);
Serial.println ("Ready\n\n");
}
void loop ()
{
int intensity = 0;
while (Serial.available() == 0)
while (Serial.available() > 0)
{
char byteIn = Serial.read();
intensity += int(byteIn) - '0';
Serial.print(byteIn);
}
}
Through Python I'd be sending a value between 0 - 255, That number should be being saved as a string and then be sent to the Arduino which would then create an integer character by character. For debugging reasons I wanted to echo back the string to Python but I haven't gotten my code to run that far yet. There is something up with the way I'm trying to send the data from Python to the Arduino, this is the Trace back I am getting:
Enter a Color value: 25
Traceback (most recent call last):
File "C:\Users\Squirrelzar\Documents\Python Proj\Arduino Serial Testing.py", line 10, in <module>
ser.write(numIn)
File "C:\Python34\lib\site-packages\serial\serialwin32.py", line 283, in write
data = to_bytes(data)
File "C:\Python34\lib\site-packages\serial\serialutil.py", line 76, in to_bytes
b.append(item) # this one handles int and str for our emulation and ints for Python 3.x
TypeError: an integer is required
Im using Python 3.4 with PySerial 2.7
Any help would be greatly appreciated..I am so lost..

Answer 1

You can send from python the integer value as a string, and read it directly in Arduino as integer using Serial.parseInt(). The next code works for me (linux, python 2.7):
Python:
import serial
ser = serial.Serial('/dev/ttyACM1', 9600)
print (ser.readline())
while True:
numIn = raw_input("Enter a Color value: ") # Returns the value as string
ser.write(numIn)
msg = ser.readline()
print (msg)
Arduino:
void setup ()
{
Serial.begin (9600);
Serial.print ("Ready\n");
}
void loop ()
{
while(Serial.available())
{
int inNumber = Serial.parseInt(); # retunrs the first valid long integer buffered
Serial.print(inNumber);
Serial.print('\n');
}
}
A comment, if you send Serial.println ("Ready\n\n"); you have to read all the new-line characters before reading other data