为什么这个 xbox 控制器监控程序有效？

Question

我有以下代码，但我不完全确定结局为何有效。

from inputs import get_gamepad
import threading

class XboxController(object):
    MAX_TRIG_VAL = pow(2, 8)
    MAX_JOY_VAL = pow(2, 15)

    def __init__(self):
        
        self.LeftJoystickY = 0
        self.LeftJoystickX = 0
        self.RightJoystickY = 0
        self.RightJoystickX = 0
        self.LeftTrigger = 0
        self.RightTrigger = 0
        self.LeftBumper = 0
        self.RightBumper = 0
        self.A = 0
        self.X = 0
        self.Y = 0
        self.B = 0
        self.LeftThumb = 0
        self.RightThumb = 0
        self.Back = 0
        self.Start = 0
        self.LeftDPad = 0
        self.RightDPad = 0
        self.UpDPad = 0
        self.DownDPad = 0
        self._monitor_thread = threading.Thread(target=self._monitor_controller, args=())
        self._monitor_thread.daemon = True
        self._monitor_thread.start()

    def read(self): # return the buttons/triggers that you care about in this methode
        x = self.LeftJoystickX
        y = self.LeftJoystickY
        a = self.A
        b = self.X # b=1, x=2
        rb = self.RightBumper
        rt = self.RightTrigger
        return [x, y, a, b, rb, rt]

    def _monitor_controller(self):
        while True:
            events = get_gamepad()
            for event in events:
                if event.code == 'ABS_Y':
                    self.LeftJoystickY = event.state / XboxController.MAX_JOY_VAL # normalize between -1 and 1
                elif event.code == 'ABS_X':
                    self.LeftJoystickX = event.state / XboxController.MAX_JOY_VAL # normalize between -1 and 1
                elif event.code == 'ABS_RY':
                    self.RightJoystickY = event.state / XboxController.MAX_JOY_VAL # normalize between -1 and 1
                elif event.code == 'ABS_RX':
                    self.RightJoystickX = event.state / XboxController.MAX_JOY_VAL # normalize between -1 and 1
                elif event.code == 'ABS_Z':
                    self.LeftTrigger = event.state / XboxController.MAX_TRIG_VAL # normalize between 0 and 1
                elif event.code == 'ABS_RZ':
                    self.RightTrigger = event.state / XboxController.MAX_TRIG_VAL # normalize between 0 and 1
                elif event.code == 'BTN_TL':
                    self.LeftBumper = event.state
                elif event.code == 'BTN_TR':
                    self.RightBumper = event.state
                elif event.code == 'BTN_SOUTH':
                    self.A = event.state
                elif event.code == 'BTN_NORTH':
                    self.Y = event.state #previously switched with X
                elif event.code == 'BTN_WEST':
                    self.X = event.state #previously switched with Y
                elif event.code == 'BTN_EAST':
                    self.B = event.state
                elif event.code == 'BTN_THUMBL':
                    self.LeftThumb = event.state
                elif event.code == 'BTN_THUMBR':
                    self.RightThumb = event.state
                elif event.code == 'BTN_SELECT':
                    self.Back = event.state
                elif event.code == 'BTN_START':
                    self.Start = event.state
                elif event.code == 'BTN_TRIGGER_HAPPY1':
                    self.LeftDPad = event.state
                elif event.code == 'BTN_TRIGGER_HAPPY2':
                    self.RightDPad = event.state
                elif event.code == 'BTN_TRIGGER_HAPPY3':
                    self.UpDPad = event.state
                elif event.code == 'BTN_TRIGGER_HAPPY4':
                    self.DownDPad = event.state

if __name__ == "__main__":
    joy = XboxController()
    while True:
       print(joy.read())

当我运行代码时，它完美运行。但是我不确定这是如何实时更新的。在 if name == 'main' 中，While 循环遍历并打印出 joy.read() 的返回值。但由于 joy 是在 while 循环之外定义的，代码如何返回并重新定义 joy 中的所有值？是线程的原因吗？我不确定并且确定可以使用一些帮助来理解这一点。谢谢！！

我试图从一个已经编写好的代码中读取一个 xbox 控制器的输入。代码有效，但我不完全明白为什么。

Answer 1

Klaus 已经声明它是由于线程

这里有一些解释可能对我有帮助，

在 while 循环中调用

joy

时，Python 会尝试在 Environments 中查找 joy 变量（Python 作用域概念遵循

LEGB (Local, Enclosing, Global and Built-in)

规则）。

joy

在我相信的本地环境中，当它被发现时，

XboxController

就会被触发。由于每次从类创建对象时都会调用构造函数

__init__

，因此您提供的代码有效！