ValueError: axes don't match array when trying to transpose

I'm fetching a frame correctly from webcam:

success, image = self.video.read()

But when I try to change the mode of my frame to grayscale using the following code:

gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

I get the following error:

    im = im[..., ::-1].transpose((0, 3, 1, 2))  # BGR to RGB, BHWC to BCHW, (n, 3, h, w)
ValueError: axes don't match array

What seems to be the problem ?

========UPDATE=========== Here is my code:

class xyx(object):
    def __init__(self):
         ...

    def __del__(self):
        self.video.release()

    def get_frame(self):
        success, image = self.video.read()
        
        print(type(image))

        #clean      
        image = np.zeros((480,640,3), 
                dtype=np.uint8)
        image = get_grayscale(image)

        ...

        #...
        x = ...

        #...
        return ...

And for the functions:

def get_grayscale(img):
    return cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

def remove_noise(img):
    return cv2.medianBlur(img,5)

def thresholdImg(img):
    return cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

The error is not deep in the code; without converting to grayscale it works. The whole problem is in the conversion from BGR to grayscale.

You didn't get that error while trying to cvtColor. You got that error while trying to transpose.

Your image has shape (480, 640, 3).

Your attempt to transpose refers to a 4th dimension, 3, which does not exist.

Hence the ValueError.