img = cv2.imread('image.jpg')
blank_image = np.zeros((1, 40, 3), np.float32)
img = np.concatenate((img, blank_image), axis=1)

ValueError: all the input arrays must have same number of dimensions

shape = img.shape
shape = list(shape)
#axis dimmension
shape[1] = 1
shape = tuple(shape)
blank_image = np.zeros(shape, np.float32)

def createBorder( ):
global img # image in which we want to append
borderType = cv.BORDER_CONSTANT
TDLU=[0 , 1, 0 , 1 ]#top,down,left,right values
img = cv.copyMakeBorder(img, TDLU[0] , TDLU[1] , TDLU[2] , TDLU[3] , borderType, None, 255)
row, col = img.shape
print(row, col)