Unable to detect face and eye with OpenCV in Python -

this code detect face , eyes using webcam getting error

traceback (most recent call last):     file "d:/acads/7.1 sem/btp/facedetect-master/6.py", line 28, in <module>       eyes = eyecascade.detectmultiscale(roi)   nameerror: name 'roi' not defined 

but when use code detect faces , eyes in image working without error

import matplotlib import matplotlib.pyplot plt import cv2 import sys import numpy np import os  facecascade = cv2.cascadeclassifier('haarcascade_frontalface_default.xml') eyecascade= cv2.cascadeclassifier('haarcascade_eye.xml')  video_capture = cv2.videocapture(0)  while true:     # capture frame-by-frame     ret, frame = video_capture.read()      faces = facecascade.detectmultiscale(frame)      (x, y, w, h) in faces:         cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)         roi = frame[y:y+h, x:x+w]      eyes = eyecascade.detectmultiscale(roi)     (ex,ey,ew,eh) in eyes:         cv2.rectangle(roi,(ex,ey),(ex+ew,ey+eh), 255, 2)      cv2.imshow('video', frame)      if cv2.waitkey(1) & 0xff == ord('q'):         break  video_capture.release() cv2.destroyallwindows() 

i think problem of indentation.

roi out of scope when go out of faces loop.

for (x, y, w, h) in faces:     cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)     roi = frame[y:y+h, x:x+w]      # eyes detection runs each face     eyes = eyecascade.detectmultiscale(roi)     (ex,ey,ew,eh) in eyes:         cv2.rectangle(roi,(ex,ey),(ex+ew,ey+eh), 255, 2)