ultra.py

import RPi.GPIO as GPIO
import time
import subprocess 
GPIO.setmode(GPIO.BCM)

TRIG = 23 
ECHO = 24

print("Distance Measurement In Progress")

GPIO.setup(TRIG,GPIO.OUT)
GPIO.setup(ECHO,GPIO.IN)

GPIO.output(TRIG, False)
print("Waiting For Sensor To Settle")
time.sleep(2)

GPIO.output(TRIG, True)
time.sleep(0.00001)
GPIO.output(TRIG, False)

while GPIO.input(ECHO)==0:
  pulse_start = time.time()

while GPIO.input(ECHO)==1:
  pulse_end = time.time()

pulse_duration = pulse_end - pulse_start

distance = pulse_duration * 17150

distance = round(distance, 2)

print("Distance:",distance,"cm")

if (distance < 100):
    print("intruder")
    python_bin = "/home/pi/.virtualenvs/cv/bin/python"
    script_file = "/home/pi/Desktop/face.py"
    subprocess.Popen([python_bin, script_file])


GPIO.cleanup()