calculating the center of a board

Am trying to print an Reversi broad given a user defined rows and columns. Am having a bit trouble with finding the center four pieces in implementing and printing the board. Here is what I have so far:

def new_game_board(columns,rows) -> [[str]]:
    ''' Creates a new game board.  Initially, a game board has the size
    BOARD_COLUMNS x BOARD_ROWS and is comprised only of strings with the
    value NONE
    '''
    board = []

    for col in range(columns):
        board.append([])
        for row in range(rows):
            board[-1].append('*')
    black = (rows+1)*columns//2
    white = rows//2
    white = columns//2

    return board

def drawBoard(board,columns,rows):
    print('  '.join(map(lambda x: str(x + 1), range(columns))))
    for y in range(rows):
        print('  '.join(board[x][y] for x in range(columns)))

How can I find the new center pieces are place accordingly to the user input? The final board should look like this:

1  2  3  4  5  6 
.  .  .  .  .  .
.  .  .  .  .  .
.  .  B  W  .  .
.  .  W  B  .  .
.  .  .  .  .  .
.  .  .  .  .  .

You have rectangle with size columns x rows so the middle is in the middle of each axis: columns/2 and rows/2.

import math

middle_start_row = math.floor(rows/2)
middle_start_col = math.floor(columns/2)