Face Detection - Python(OpenCV)

import cv2

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
#Read the input image
img = cv2.imread('test.png')
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)
#Display the output
cv2.imshow('img', img)
cv2.waitKey()