修复 NameError

Question

我正在编写一个程序来与两个玩家一起玩井字游戏。我已经完成了基本代码（尽管效率很低），但我一直收到一条错误消息，提示未定义 player2。我已经尝试了很多方法来修复错误，但想知道你们是否有任何想法。它在第一个 player1 == player2 条件下被捕获。这是代码：

   def main():
    board1 = [" "," "," "]
    board2 = [" "," "," "]
    board3 = [" "," "," "]
    game(board1,board2,board3)
def play1():
    global player1
    player1 = int(input("Player 1, where would you like to move? "))
    return player1
def play2():
    global player2
    player2 = int(input("Player 2, where would you like to move? "))
    return player2
def game(brd1,brd2,brd3):
    isvalid = False
    while(not(isvalid)):
        play1()
        try:
            if player1 == player2:
                print("You can't both go to the same spot!")
        except NameError:
            if player1 == 0:
                brd1.pop(0)
                brd1.insert(0,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 1:
                brd1.pop(1)
                brd1.insert(1,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 2:
                brd1.pop(2)
                brd1.insert(2,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 3:
                brd2.pop(0)
                brd2.insert(0,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 4:
                brd2.pop(1)
                brd2.insert(1,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 5:
                brd2.pop(2)
                brd2.insert(2,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 6:
                brd3.pop(0)
                brd3.insert(0,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 7:
                brd3.pop(1)
                brd3.insert(1,"x")
                print(brd1)
                print(brd2)
                print(brd3)
            elif player1 == 8:
                brd3.pop(2)
                brd3.insert(2,"x")
                print(brd1)
                print(brd2)
                print(brd3)
        play2()
        if player2 == player1:
            print("You can't both go to the same spot!")
        elif player2 == 0:
            brd1.pop(0)
            brd1.insert(0,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 1:
            brd1.pop(1)
            brd1.insert(1,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 2:
            brd1.pop(2)
            brd1.insert(2,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 3:
            brd2.pop(0)
            brd2.insert(0,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 4:
            brd2.pop(1)
            brd2.insert(1,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 5:
            brd2.pop(2)
            brd2.insert(2,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 6:
            brd3.pop(0)
            brd3.insert(0,"o")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 7:
            brd3.pop(1)
            brd3.insert(1,"x")
            print(brd1)
            print(brd2)
            print(brd3)
        elif player2 == 8:
            brd3.pop(2)
            brd3.insert(2,"o")
            print(brd1)
            print(brd2)
            print(brd3)
if __name__ == '__main__':
    main()

Answer 1

您的变量 - player1 和 player2 - 在本地范围（play1 和 play2）中定义，您尝试在该范围之外访问它们.在函数的开头，键入 global player1（或 player2）作为它自己的行以在全局范围内定义它。还要在所有函数之上添加 player1, player2 = None, None 以启动它。至于为什么在错误中指定player2，那是因为它是条件中的第一个变量，而Python评估left-to-right。

Answer 2

由于您的错误提示玩家 2 未定义，请尝试添加 try except 条件以检查玩家 2 是否已定义。如果它达到 NameError，它可以继续游戏（打印你的棋盘），否则，通过你的 if 条件。

while(not(isvalid)):
    play1()
    try:
    # Try going through all your conditions
         if player 1 == player 2:
         ...
    except NameError:
    # But if your player 2 is not defined, go through them all except the player 1 == player 2 clause
         if player 1 == 0:
         .....
             print(brd1)
              ....

Answer 3

您只在循环中调用 play1()。您还需要 play2()。但是，这不会解决您的问题，因为 player1 和 player2 是在函数中本地定义的。要解决此问题，请在 play1() 中添加 global player1，并在 play2() 中添加 global player2。代码看起来像这样

def play1():
    global player1
    player1 = int(input("Player 1, where would you like to move? "))
def play2():
    global player2
    player2 = int(input("Player 2, where would you like to move? "))

循环：

while(not(isvalid)):
    play1()
    play2() 
    if player2 == player1:

解决此问题的另一种方法是 return 它们，如下所示：

def play1():
    player1 = int(input("Player 1, where would you like to move? "))
    return player1
def play2():
    player2 = int(input("Player 2, where would you like to move? "))
    return player2

然后在你的循环中：

while(not(isvalid)):
        player1 = play1()
        player2 = play2()
        if player2 == player1:

这样可以避免全局变量。

编辑：为了在每回合后打印棋盘，在文件开头初始化 player2 = None：

player2 = None
def main():
...

您仍然需要 play1() 和 play2()

中的全局变量

def play1():
    global player1
    player1 = int(input("Player 1, where would you like to move? "))
def play2():
    global player2
    player2 = int(input("Player 2, where would you like to move? "))

那么不需要对循环进行适配。

Answer 4

从您的代码中可以清楚地看出，player1 和 player2 在 game 方法的第二行进行了初始化，但未定义。您可能需要定义一些值。

添加这一行

player1 = player2 = None

此外，在查看您的代码后，我建议尝试在开始时将变量定义到全局范围。

global player1, player2
player1 = player2 = None

修复 NameError

Fixing a NameError

python

nameerror