2_counter.py

import RPi.GPIO as GPIO
import time
#1
PINS = [7,15,16]
COUNTER = 0
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)

def Setup():
  for p in PINS:        
    GPIO.setup(p,GPIO.OUT)

def Display(bits):
  #2
  bits = bits.zfill(3)
  for i in range(len(bits)):
	GPIO.output(PINS[i],int(bits[i]))

def Count():
  global COUNTER
  COUNTER += 1
  if (COUNTER > 7):
    COUNTER = 0
  #3
  bin_number = bin(int(COUNTER))
  Display(bin_number[2:])
  time.sleep(1)
    
def loop():
  try:
    while True:
      Count()
  #4
  except KeyboardInterrupt:
    pass
  finally:
    GPIO.cleanup()
    
Setup()

loop()