createTrackbar() does not work.

[MainForm]

I want to make some trackbar by opencv.
But, It doesn't work.
Program just quit after call createTrackbar() function.
So, I uninstalled this opencv version I download at this git.
And, I reinstalled opencv of recent version.
And, It worked.

here is my code.

from os import truncate
import cv2
import numpy as np

frame = np.zeros((500,500,3),np.uint8)

WindowTitle = 'TrackBar'
cv2.namedWindow(WindowTitle)

def trackbar_callback(color,value):
frame[:,:,color] = value

cv2.createTrackbar('r',WindowTitle,0,255,lambda v:
trackbar_callback(2,v))

cv2.createTrackbar('g',WindowTitle,0,255,lambda v:
trackbar_callback(1,v))

cv2.createTrackbar('b',WindowTitle,0,255,lambda v:
trackbar_callback(0,v))

while True:

cv2.imshow(WindowTitle,frame)

if cv2.waitKey(1) == 27:
    break

cv2.destroyAllWindows()