Eye Detection - Python(OpenCV)

import cv2

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye_tree_eyeglasses.xml')

#Read the input image
#img = cv2.imread('test.png')
cap = cv2.VideoCapture(0) #zero for webcam

while cap.isOpened():
    _, img = cap.read()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.1, 4)

    for(x, y, w, h) in faces:
        cv2.rectangle(img, (x,y), (x+w, y+h), (255, 0, 0), 3)
        roi_gray = gray[y:y+h, x:x+w]
        roi_color = img[y:y+h, x:x+w]
        eyes = eye_cascade.detectMultiScale(roi_gray)
        for(ex, ey, ew, eh) in eyes:
            cv2.rectangle(roi_color, (ex, ey), (ex+ew, ey+eh), (0, 255, 0), 5)
    #Display the output
    cv2.imshow('img', img)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()