import numpy as np
import cv2

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
# if face_cascade.empty(): raise Exception("your face_cascade is empty. are you sure, the path is correct ?")

eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')
# if eye_cascade.empty(): raise Exception("your eye_cascade is empty. are you sure, the path is correct ?")

video = cv2.VideoCapture(0)
while(video.isOpened()):
    ret, frame = video.read()

    # if frame not None:
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
    for (x,y,w,h) in faces:
        cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
        roi_gray = gray[y:y+h, x:x+w]
        roi_color = frame[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),2)
    cv2.imshow('Video', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

video.release()
cv2.destroyAllWindows()