Sign not displaying on Pygame window when clicking (tictactoe)

I am coding a tictactoe game and I have something similar to the code in this link.

When the board is clicked, it doesn't write anything (X or O). I can't seem to figure out what is the problem after trying multiple times. How could that be fixed?

import pygame
import sys
# ? 2019 TheFlyingKeyboard and released under MIT License
# theflyingkeyboard.net
def map_mouse_to_board(x, y):
    if x < gameSize / 3:
        column = 0
    elif gameSize / 3 <= x < (gameSize / 3) * 2:
        column = 1
    else:
        column = 2
    if y < gameSize / 3:
        row = 0
    elif gameSize / 3 <= y < (gameSize / 3) * 2:
        row = 1
    else:
        row = 2
    return column, row
def draw_board(board):
    myFont = pygame.font.SysFont('Tahoma', gameSize // 3)
    for y in range(3):
        for x in range(3):
            if board[y][x] == xMark:
                color = xColor
            else:
                color = oColor
            text_surface = myFont.render(board[y][x], False, color)
            screen.blit(text_surface, (y * (gameSize // 3) + margin + (gameSize // 18), x * (gameSize // 3) + margin))
def is_full(board):
    return not any(None in sublist for sublist in board)
def get_winner(board):
    # Diagonals
    if ((board[0][0] == board[1][1] and board[1][1] == board[2][2]) \
            or (board[0][2] == board[1][1] and board[1][1] == board[2][0])) and board[1][1] is not None:
        return board[1][1]
    for i in range(3):
        if board[i][0] == board[i][1] and board[i][1] == board[i][2] and board[i][0] is not None:  # Rows
            return board[i][0]
        if board[0][i] == board[1][i] and board[1][i] == board[2][i] and board[0][i] is not None:  # Columns
            return board[0][i]
    return None
def draw_lines():
    # Vertical lines
    pygame.draw.line(screen, lineColor, (margin + gameSize // 3, margin),
                     (margin + gameSize // 3, screenSize - margin), lineSize)
    pygame.draw.line(screen, lineColor, (margin + (gameSize // 3) * 2, margin),
                     (margin + (gameSize // 3) * 2, screenSize - margin), lineSize)
    # Horizontal lines
    pygame.draw.line(screen, lineColor, (margin, margin + gameSize // 3), (screenSize - margin, margin + gameSize // 3),
                     lineSize)
    pygame.draw.line(screen, lineColor, (margin, margin + (gameSize // 3) * 2),
                     (screenSize - margin, margin + (gameSize // 3) * 2), lineSize)
screenSize = 1920
margin = 50
gameSize = 1920 - (2 * margin)
lineSize = 10
backgroundColor = (0, 0, 0)
lineColor = (255, 255, 255)
xColor = (200, 0, 0)
oColor = (0, 0, 200)
xMark = 'X'
oMark = 'o'
board = [[None, None, None], [None, None, None], [None, None, None]]
currentMove = 'X'
pygame.init()
screen = pygame.display.set_mode((screenSize, screenSize))
pygame.display.set_caption("Tic Tac Toe")
pygame.font.init()
myFont = pygame.font.SysFont('Tahoma', gameSize // 3)
screen.fill(backgroundColor)
canPlay = True
draw_lines()
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_r:
                board = [[None, None, None], [None, None, None], [None, None, None]]
                screen.fill(backgroundColor)
                draw_lines()
                canPlay = True
            if event.key == pygame.K_ESCAPE:
                pygame.quit()
                sys.exit()
        if event.type is pygame.MOUSEBUTTONDOWN and canPlay:
            (mouseX, mouseY) = pygame.mouse.get_pos()
            (column, row) = map_mouse_to_board(mouseX, mouseY)
            if board[column][row] is None:
                board[column][row] = currentMove
                if currentMove == xMark:
                    currentMove = oMark
                else:
                    currentMove = xMark
                draw_board(board)
                winner = get_winner(board)
                if winner is not None:
                    myFont = pygame.font.SysFont('Tahoma', screenSize // 5)
                    text_surface = myFont.render(str(winner) + " has won!", False, lineColor)
                    screen.blit(text_surface, (margin, screenSize // 2 - screenSize // 10))
                    canPlay = False
                else:
                    if is_full(board):
                        myFont = pygame.font.SysFont('Tahoma', screenSize // 5)
                        text_surface = myFont.render("Draw!", False, lineColor)
                        screen.blit(text_surface, (screenSize // 10, screenSize // 2 - screenSize // 10))
    pygame.display.update()

Solution

Let me refer to Difference between == and is operator in Python:

The Equality operator (==) compares the values of both the operands and checks for value equality. Whereas the is operator checks whether both the operands refer to the same object or not.

Hence if you want to test if event.type is equal to pygame.MOUSEBUTTONDOWN, you have to use == rather than is:

~~if event.type is pygame.MOUSEBUTTONDOWN and canPlay:~~

if event.type == pygame.MOUSEBUTTONDOWN and canPlay: