RuntimeError: No access to /dev/mem. Try running as root!

Question

I'm new to RPI and to Python 3 and I have a problem running this code on a RPI 2.

import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
redled = 4
greenled = 26
GPIO.setup(redled, GPIO.OUT)
GPIO.setup(greenled, GPIO.OUT)
count = 1
while count < 100000:
 GPIO.output(redled, 1)
 GPIO.output(greenled, 1)
 time.sleep(.1)
 GPIO.output(redled, 0)
 GPIO.output(greenled, 0)
 time.sleep(.1)
 count = count + 1
GPIO.cleanup()

I get this error.

Traceback (most recent call last): File "/home/pi/testreactionrepeat.py", line 7, in GPIO.setup(redled, GPIO.OUT) RuntimeError: No access to /dev/mem. Try running as root!

I was using this code with no problems a couple of days ago and can't figure out what I'm doing wrong now. I found a similar problem and the answer was to run "sudo su" but I get a syntax error when I try that.

• Steve Robillard: Please edit your question and add the specific error sudo su is returning.

Answer 1

Let's assume that your program is called

program.py

Open terminal and type

sudo python program.py 

This will run your python program as root giving it the necessary permissions to access/modify the GPIO pins.

• nashville_bill: I get this when I type sudo python reactionrepeat.py into terminal. Traceback (most recent call last): File "reactionrepeat.py", line 3, in <module> GPIO.setmode(GPIO.BCM) AttributeError: 'module' object has no attribute 'setmode'
• evolutionizer: can you run "sudo apt-get update && sudo apt-get upgrade" in terminal, this will update your system with the latest software and hopefully with the latest RPi.GPIO modules and thuis fix this issue.
• nashville_bill: I did the update/upgrade, and it appeared to go well. However, my code still won't run, even though it ran just fine a couple of days before I had the problem. I still get the same messages as before when I run the program and when I type in sudo python reactionrepeat.py. Could this be a hardware problem?
• evolutionizer: @nashville_bill no this is definitely a software problem. Are you on the latest raspbian OS?
• user43492: I'm getting this experience with Ubuntu Mate 15.10 when trying to use dot3k.