Controlling fan speed by proximity

from bottle import route, run, template, request
import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BOARD)

trig = 16
echo = 18

GPIO.setup(trig, GPIO.OUT)
GPIO.setup(echo, GPIO.IN)

GPIO.setmode(GPIO.BOARD)

motorspeedPin = 8

DIRA = 10
DIRB = 22

GPIO.setup(motorspeedPin, GPIO.OUT)
GPIO.setup(DIRA, GPIO.OUT)
GPIO.setup(DIRB, GPIO.OUT)

pwmPIN = GPIO.PWM(motorspeedPin, 100)

pwmPIN.start(0)


lastMotorPower = 70
isMotorEnabled = False

def turnOff():
        pwmPIN.ChangeDutyCycle(0)


def calculateDistance():
    GPIO.output(trig, GPIO.HIGH)

    time.sleep(0.00001)
    GPIO.output(trig, GPIO.LOW)

    start = time.time()
    stop = time.time()

    while GPIO.input(echo) == 0:
        start = time.time()

    while  GPIO.input(echo) == 1:
        stop = time.time()

    duration = stop - start

    distance = 34300/2 * duration

    if distance < 0.5 and distance > 400:
        return 0
    else:
        return distance

@route('/')
def index():
    return template('index.html')


@route('/start')
def start():
    global isMotorEnabled
    isMotorEnabled = True
    return 'ok'


@route('/stop')
def start():
    global isMotorEnabled
    isMotorEnabled = False
    return 'ok'


@route('/refresh')
def refresh():
    global lastMotorPower
    global isMotorEnabled
    
    if isMotorEnabled == True:
        dist = calculateDistance()
        motorPower = dist + 20
        motorPower = min(100, motorPower)

        if (abs(lastMotorPower - motorPower) > 5):
            lastMotorPower = motorPower
        
        print(motorPower, lastMotorPower)
        
        pwmPIN.ChangeDutyCycle(lastMotorPower)
        
        GPIO.output(DIRA, GPIO.HIGH)
        GPIO.output(DIRB, GPIO.LOW)

        return '%d' % lastMotorPower
    else:
        turnOff()
    
    return 0

try:
    run(host = '0.0.0.0', port = '5000')

except KeyboardInterrupt:
    pass


GPIO.cleanup()
turnOff()