import RPi.GPIO as GPIO
from time import sleep

ledpin = 18			# PWM pin connected to LED

GPIO.setwarnings(False)			#disable warnings
GPIO.setmode(GPIO.BOARD)		#set pin numbering system
GPIO.setup(ledpin,GPIO.OUT)

pi_pwm = GPIO.PWM(ledpin,1000)		#create PWM instance with frequency
pi_pwm.start(0)				#start PWM of required Duty Cycle 

while True:
    for duty in range(0,101,1):
        pi_pwm.ChangeDutyCycle(duty) #provide duty cycle in the range 0-100
        sleep(0.01)
    sleep(0.5)
    
    for duty in range(100,-1,-1):
        pi_pwm.ChangeDutyCycle(duty)
        sleep(0.01) 
    sleep(0.5)