ValueError：使用序列设置数组元素

Question

When I am trying to run this piece of the code i am getting following exceptions. I have tried a lot of things. I know I am trying to assign a sequence to numpy array single value.

  grid = np.zeros((401, 401))
        for timestamps,poly in sorted(left_camera.iteritems()):
            polygonal = left_camera[timestamps]
            for i in range(0,len(polygonal)):
                if len(polygonal)>0:
                    row = np.int32(polygonal[i][0] * -10 + 200)
                    coloumn = np.int32(polygonal[i][1] * -10 + 200)
                    grid[row,coloumn] = np.array([255,0,0])
        cv2.imshow("image_name", grid)
        cv2.waitKey(0)

exception i am getting here:

grid[row,coloumn] = np.array([255,0,0])

ValueError: setting an array element with a sequence.

Here left_camera is my dict value with time stamps and some polygon is a list.

any solution will be much appreciated. I am new to this .

Thanks in advance!!

Answer 1

The error points that np.array([255,0,0]) cannot fit in the matrix as it is not an expected value to be inserted in the matrix of shape (401, 401) . When you create the matrix = np.zeros((401, 401)) , it creates a matrix with height = 401 and width = 401. Since it has no third dimension, you can only substitute a single integer in this matrix as:

grid = np.zeros((401, 401))
grid[10, 10] = 20      # Works perfectly fine
grid[10, 10] = np.array([10, 20, 20])   # Raises Error

To fix this issue, you need to pass the third dimension while creating the matrix as:

grid = np.zeros((401, 401, 3))
grid[10, 10] = np.array([10, 20, 20])   # Works perfectly fine