I am currently bread-boarding two LEDs with 560 mOh resistors connected to the RPi over a ribbon cable that connects to the breadboard with a Pi Cobbler.

The problem I am getting isn't with the hardware, it's with the script. When I run it, I get this error:

led_g-r.py:11: RuntimeWarning: This channel is already in use, continuing anyway.  
Use GPIO.setwarnings(False) to disable warnings.
led_g-r.py:16: RuntimeWarning: This channel is already in use, continuing anyway.  
Use GPIO.setwarnings(False) to disable warnings.
Traceback (most recent call last):
  File "led_g-r.py", line 59, in 
  File "led_g-r.py", line 56, in main
  File "led_g-r.py", line 33, in flash
    for flash in range(0, repeat):
AttributeError: LED instance has no attribute '__trunc__'

Can anyone see the problem in my code (included below). I wrote the script myself and I'm rather new to python so I probably will have a few problems/code that could be done better.

I wrote this with a class so that I could change around my projects with different LED configurations.

This is the code:

import RPi.GPIO as GPIO
import time       


class LED:                                 
        def __init__(self, color, pin):
                self.color = color.lower()
                if self.color == 'green':
                        GREEN_LED = pin                          
                        GPIO.setup(GREEN_LED, GPIO.OUT)             
                        self.LED = 'GREEN_LED'                      

                elif self.color == 'red':
                        RED_LED = pin
                        GPIO.setup(RED_LED, GPIO.OUT)
                        self.LED = 'RED_LED'

        def OFF():                           

                GPIO.output(self.LED, False)

        def ON():
                GPIO.output(self.LED, True)

        def flash(repeat=1, length=1, cust=0):  # repeat is automatically 1
                                        # cust is automatically 0
                                        # length is automatically 1:
                                        # 1 = short-on/off for 3sec.
                                        # 2 = medium-on for 5sec. off for 3sec.
                                        # 3 = long-on for 10sec. off for 3 sec.
                                        # 4 = custom-set cust=length on in sec.
                for flash in range(0, repeat):       
                        if length == '1':
                        elif length == '2': 
                        elif length == '3':
                        elif length == '4':

        def SOS(repeat=1):
                flash(3, 1)
                flash(3, 3)
                flash(3, 1)                          

def main():                              
        green = LED('green', 18)

        red = LED('red', 23)                



PS...If it helps, I can post a picture of the configuration. I also have connected my USB to TTL Console Cable so I can connect to the pi without having to use my awful screen.

1 Answer 1


Restart your Pi, and then use this code to clean up the GPIO pins when your program exits:


The next time your program runs it should work.

  • This will get rid of the Attribute Error? Thanks! I will try this! But, overall, is my code good/okay? I'm trying to get good at Python, but I've taught myself via books and videos and Stack Exchanges (Here, Ask Ubuntu, Stack Overflow), so I don't know if my code is ok or not. Thanks! Commented Sep 15, 2013 at 12:06
  • 1
    I think you're seeing the attribute error because of the runtime warning about the channel already being in use. If you fix the runtime warning, the attribute error should go away.
    – Steve
    Commented Sep 15, 2013 at 12:10

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