Tkinter绑定：如何理解for循环中的作用域？

Question

这里似乎已经有人问过这个问题：

• Events and Bindings in tkinter does not work in loop
• tkinter bind function with variable in a loop
• Tkinter assign button command in loop with lambda

但我不明白答案。 下面是同一问题的另一个代码示例：

如何理解for循环中的作用域？

[edit]我的“orient”函数定义如下：[/edit]

orient = lambda snake, direction: snake.changeDirection(direction)

我尝试用这个循环分配tkinter绑定：

for player in Parameters.players:
    snake = self.snakes[player]
    self.root.bind(bindings[player]['up'], lambda event : orient(snake, Direction.N))
    self.root.bind(bindings[player]['left'], lambda event : orient(snake, Direction.W))
    self.root.bind(bindings[player]['down'], lambda event : orient(snake, Direction.S))
    self.root.bind(bindings[player]['right'], lambda event : orient(snake, Direction.E))

但是这两个绑定被分配给了最后一条蛇

所以我试着“手动”循环：

player1 = Parameters.players[0]
snake1 = self.snakes[player1]
self.root.bind(bindings[player1]['up'], lambda event : orient(snake1, Direction.N))
self.root.bind(bindings[player1]['left'], lambda event : orient(snake1, Direction.W))
self.root.bind(bindings[player1]['down'], lambda event : orient(snake1, Direction.S))
self.root.bind(bindings[player1]['right'], lambda event : orient(snake1, Direction.E))

player2 = Parameters.players[1]
snake2 = self.snakes[player2]
self.root.bind(bindings[player2]['up'], lambda event : orient(snake2, Direction.N))
self.root.bind(bindings[player2]['left'], lambda event : orient(snake2, Direction.W))
self.root.bind(bindings[player2]['down'], lambda event : orient(snake2, Direction.S))
self.root.bind(bindings[player2]['right'], lambda event : orient(snake2, Direction.E))

它起作用了（每一条蛇都有自己的束缚）

lambda函数实际上是如何创建的？为什么它“捕获”变量并因此被覆盖而不是保留其值

Answer 1

最终代码是：

orient = lambda snake, direction: snake.changeDirection(direction)
for player in Parameters.players:
    snake = self.snakes[player]
    self.root.bind(bindings[player]['up'], lambda event, snake=snake : orient(snake, Direction.N))
    self.root.bind(bindings[player]['left'], lambda event, snake=snake : orient(snake, Direction.W))
    self.root.bind(bindings[player]['down'], lambda event, snake=snake : orient(snake, Direction.S))
    self.root.bind(bindings[player]['right'], lambda event, snake=snake : orient(snake, Direction.E))

注意lambda定义中的“snake=snake”

此处解释：Creating functions in a loop