import RPi.GPIO as GPIO
import time

t,e,l = 7,8,4

gpio.setmode(gpio.BCM)
gpio.setup(t,gpio.OUT)
gpio.setup(e,gpio.IN)
gpio.setup(l,gpio.OUT)

def d():
    gpio.output(t,1)
    time.sleep(0.00001)
    gpio.output(t,0)

    while gpio.input(e) == 0:
        s = time.time()

    while gpio.input(e) == 1:
        pass

        f = time.time()
        p = f-s 
        return p*17150/2
    while True:
        dist = d()
        gpio.output(l, dist <= 25)
        time.sleep(0.1)
d()