UnboundLocalError: 无法访问未赋值的局部变量 'currentPlayer

Question

我不太明白这个错误。'currentPlayer'在第13行被声明和定义了，而且是全局的。为什么在我的ToggleTurn()方法里它会变成未绑定的呢？

错误信息：

Traceback (most recent call last):
  File "...main.py", line 83, in <module>
    PlacePiece(currentPlayer,5)
  File "...main.py", line 51, in PlacePiece
    ToggleTurn()
  File "...main.py", line 28, in ToggleTurn
    if currentPlayer == 1:
       ^^^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'currentPlayer' where it is not associated with a value

import pygame as pg
pg.init()

currentPlayer = 2 # 1 = o and 2 = x

def ToggleTurn():
    if currentPlayer == 1:
        currentPlayer = 2
    elif currentPlayer == 2:
        currentPlayer = 1
    else:
        print("ERROR: Could not progress to the next turn!")
        return False
    return True

def PlacePiece(piece,slot):
    if not (1,slot) in pieceList or not (2,slot) in pieceList:
        pieceList.append((piece,slot))
        ToggleTurn()
    else:
        print("GAME NOTE: A piece has already been placed there!")



RUN = True
while RUN:
    #event handler
    for event in pg.event.get():
        if event.type == pg.QUIT:
            RUN = False
        if event.type == pg.KEYDOWN:
            if event.key == pg.K_KP1:
                PlacePiece(currentPlayer,1)
            #elif for the other numpad buttons
    pg.display.update()

我试着通过值传递currentPlayer，但这样TogglePlayer()方法只更新了局部变量。

Answer 1

这个值不是全局的。如果想让它变成全局的，你需要在'def ToggleTurn'这一行后面加上一行'global currentPlayer'，这样才能在函数里修改这个值。如果你只是想获取currentPlayer的值，而不想修改它，那么你应该在代码的最开始加上'global currentPlayer'这一行。