There was an error trying to code the implementation of a 3*3 Tiktecto game competing with ai.

if __name__ == "__main__":
    while True:
        gameScreen = [",",",",",",",",""]
        player, AI = choosePlayer()
        drawingBoard(gameScreen)

        if player == 'X':
        while True:
            putPlayerStone(gameScreen, player)
            checkWinner(gameScreen, player, AI)
            drawingBoard(gameScreen)
            putAIStone(gameScreen, player, AI)
            checkWinner(gameScreen, player, AI)
            drawingBoard(gameScreen)

def choosePlayer():
  print ('Enter uppercase letter X or O')
  while True:
    chosen = input ('uppercase letter X or O input') #
    if chosen!='O' and chosen !='X':
      print ('Re-enter the letter O or X')
      continue
    elif chosen == 'O':
        return 'O','X'
    elif chosen == 'X':
        return 'X','O'

def drawingBoard(screen):
  print()
  print('____________________________________________')
  print(' '+screen[6]+' '+'|'+' '+screen[7]+' '+'|'+' '+screen[8])
  print('____________________________________________')
  print(' '+screen[3]+' '+'|'+' '+screen[4]+' '+'|'+' '+screen[5])
  print('____________________________________________')
  print(' '+screen[0]+' '+'|'+' '+screen[1]+' '+'|'+' '+screen[2])
  print('____________________________________________')
  print()

def putPlayerStone(screen, mark):
  while True:
    print ('>>Select stone position: ',end=') #end=' is one command
    position = input()
    if position not in ['1','2','3','4','5','6','7','8','9']:
      continue
    if screen[int(position)-1]!= '':
      continue
    else:
      break
  screen[int(position)-1] = mark
  return position, screen

def putAIStone (screen, player, AI):
  AI_willPut_here=[]

  Put_player = [0, 0, 0, 0, 0, 0, 0, 0, 0]
  for i in range(0,9):
      if player == screen[i]:
          Put_player[i] = True

  Put_AI = [0, 0, 0, 0, 0, 0, 0, 0, 0]
  for i in range(0,9):
      if AI == screen[i]:
          Put_AI[i] = True

  hldx = 8
  while hldx >= 2:
    if Put_AI[hldx -1]==True:
        if Put_AI [hldx -1-1]==True:
            AI_willPut_here.append(hldx -1+1)
        elif Put_player[hldx-1+1] == True:
            AI_willPut_here.append(hldx -1-1)
    elif Put_AI[hldx -1-1] == True and Put_AI[hldx -1+1] == True:
        AI_willPut_here.append(hldx -1)
    hldx -= 3

    vldx = 4

  while vldx <= 6:
    if Put_AIr[vldx -1] == True:
        if Put_AI[vldx-1+3] == True:
            AI_willPut_here.append(vldx -1-3)
        elif Put_AI[vldx -1-3] == True:
            AI_willPut_here.append(vldx -1+3)    
    elif Put_AI[vldx -1+3] == True and Put_AI[vldx -1-3] == True:
        AI_willPut_here.append(vldx -1)
    vldx += 1    

    if Put_AI[5-1] == True:
        if Put_AI[7-1] == True:
            AI_willPut_here.append(3-1)
        elif Put_AI[7-1] == True:
            AI_willPut_here.append(3-1)
        elif Put_AI[7-1] == True:
            AI_willPut_here.append(3-1)
        elif Put_AI[7-1] == True:
            AI_willPut_here.append(3-1) 
    if Put_AI[7-1] == True and Put_AI[3-1] == True:
        AI_willPut_here.append(5-1)
    if Put_AI[9-1] == True and Put_AI[1-1] == True:
        AI_willPut_here.append(5-1)

  for i in range(0,len(AI_willPut_here)):
      if screen[AI_willPut_here[i]] == '':
          available.append(AI_willPut_here[i])
  available = random.choice(available)
  screen[int(available)] = AI
  return screen

def checkWinner(screen,player,AI):
  playerPut = [0, 0, 0, 0, 0, 0, 0, 0, 0]
  for i in range(0.9):
    if player == screen[i]:
        playerPut[i] = True
  vldx = 7
  while vldx <= 9:
    if playerPut[vldx-1] == True and playerPut[vldx-1-3] == True and playerPut[vldx-1-6] == True:
        playerWin(screen)
        return True
    vldx += 1

  hldx = 7
  while hldx >= 1:
    if playerPut[hldx-1] == True and playerPut[hldx-1+1] == True and playerPut[hldx-1+2] == True:
        playerWin(screen)
        return True
    hldx -= 3

    if playerPut[7-1]==True and playerPut[5-1]==True and     playerPut[3-1]==True:
        playerWin(screen)
        return True
    elif playerPut[9-1]==True and playerPut[5-1]==True and playerPut[1-1]==True:
        playerWin(screen)
        return True

  for i in range(0,9):
          if screen[i]=='':
              break
          elif i==8:
              drawingGameScreen(screen)
              print ("Draw")
              return True
'''