Почему не объявляется переменная

import random
import turtle
 
turn = random.randint(0, 1)
choose = 0
grid = [1, 2, 3, 4, 5, 6, 7, 8, 9]
playerX = []
player0 = []
 
 
def errorX(a):
 
    if a in grid:
        playerX.append(a)
        printX(xPos[a - 1], yPos[a - 1])
        turn = 0
        grid.remove(a)
    else:
        print("Error")
 
 
def error0(a):
    if a in grid:
        player0.append(a)
        print0(xPos[a - 1], yPos[a - 1])
        turn = 1
        grid.remove(a)
    else:
        print("Error")
 
 
def printX(x, y):
    turtle.penup()
    turtle.setposition(x, y)
    turtle.pendown()
    turtle.color("red")
    turtle.setposition(x + 100, y - 100)
    turtle.penup()
    turtle.setposition(x, y - 100)
    turtle.pendown()
    turtle.setposition(x + 100, y)
 
 
def print0(x, y):
    turtle.penup()
    turtle.setposition(x + 50, y - 100)
    turtle.pendown()
    turtle.circle(50)
 
 
turtle.shape("turtle")
turtle.color("blue")
turtle.speed(100)
turtle.pensize(5)
 
turtle.forward(100)
size = 300
turtle.setposition(size, 0)
turtle.setposition(300, 300)
turtle.setposition(0, 300)
turtle.setposition(0, 0)
turtle.setposition(0, 100)
turtle.setposition(300, 100)
turtle.setposition(300, 200)
turtle.setposition(0, 200)
turtle.setposition(0, 300)
turtle.setposition(100, 300)
turtle.setposition(100, 0)
turtle.setposition(200, 0)
turtle.setposition(200, 300)
 
xPos = [0, 100, 200, 0, 100, 100, 200, 0, 100, 200]
yPos = [300, 300, 300, 200, 200, 200, 100, 100, 100]
 
while True:
    if turn == 1:
        choose = int(input("ход Х.Введите номер ячейки: "))
        errorX(choose)
        turn = 0
    elif turn == 0:
        choose = int(input("ход 0 введи номер ячейки: "))
        error0(choose)
        turn = 1

turn = 1