Python code that reads in distance from HC-SR04 sensor on RasparryPi3

sonar.py

# Modified from https://pimylifeup.com/raspberry-pi-distance-sensor
import RPi.GPIO as GPIO
import time

try:
      GPIO.setmode(GPIO.BOARD)

      PIN_TRIGGER = 7
      PIN_ECHO = 11

      GPIO.setup(PIN_TRIGGER, GPIO.OUT)
      GPIO.setup(PIN_ECHO, GPIO.IN)

      GPIO.output(PIN_TRIGGER, GPIO.LOW)

      print "Waiting for sensor to settle"

      time.sleep(2)

      print "Calculating distance"
      
      while True:

            GPIO.output(PIN_TRIGGER, GPIO.HIGH)

            time.sleep(1)

            GPIO.output(PIN_TRIGGER, GPIO.LOW)

            while GPIO.input(PIN_ECHO)==0:
                  pulse_start_time = time.time()
            while GPIO.input(PIN_ECHO)==1:
                  pulse_end_time = time.time()

            pulse_duration = pulse_end_time - pulse_start_time
            distance = round(pulse_duration * 17150, 2)
            print "Distance:",distance,"cm"

finally:
      GPIO.cleanup()