python - __init__() 得到意外的关键字参数 'y'

Question

我正在阅读《绝对初学者的 Python 编程》一书，并决定通过制作自己的游戏来测试我的一些技能。这个游戏基本上是“不要被飞行的尖刺击中”，我遇到了一个问题。使用此代码运行它时:

class Player(games.Sprite):
    """The player that must dodge the spikes."""

    def update(self):
        """Move to the mouse."""
        self.x = games.mouse.x
        self.y = games.mouse.y
        self.check_collide()

    def check_collide(self):
        """Check for a collision with the spikes."""
        for spike in self.overlapping_sprites:
            spike.handle_collide()


def main():


    pig_image = games.load_image("Mr_Pig.png")
    the_pig = Player(image = pig_image,
                     x = games.mouse.x,
                     y = games.mouse.y)
    games.screen.add(the_pig)
    games.mouse.is_visible = False
    games.screen.event_grab = True

    games.screen.mainloop()

main()

我没问题。但是当我想使用“init”时，如以下代码所示:

class Player(games.Sprite):
    """The player that must dodge the spikes."""

    def update(self):
        """Move to the mouse."""
        self.x = games.mouse.x
        self.y = games.mouse.y
        self.check_collide()

    def check_collide(self):
        """Check for a collision with the spikes."""
        for spike in self.overlapping_sprites:
            spike.handle_collide()

    def __init__(self):
        """A test!"""
        print("Test.")


def main():

    pig_image = games.load_image("Mr_Pig.png")
    the_pig = Player(image = pig_image,
                     x = games.mouse.x,
                     y = games.mouse.y)
    games.screen.add(the_pig)
    games.mouse.is_visible = False
    games.screen.event_grab = True

    games.screen.mainloop()

main()

运行游戏时出现此错误:

File "run.py", line 85, in main
    y = games.mouse.y)
TypeError: __init__() got an unexpected keyword argument 'y'.

Answer 1

这一行:

the_pig = Player(image = pig_image,
                 x = games.mouse.x,
                 y = games.mouse.y)

(某种程度上)相当于:

the_pig = Player.__init__(image = pig_image,
                 x = games.mouse.x,
                 y = games.mouse.y)

这意味着您的 __init__ 应该接受参数 image、x 和 y，但您已经定义了它如:

def __init__(self):
    """A test!"""
    print("Test.")

如果你想简单地传递所有参数，你可以这样做:

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    """A test!"""
    print("Test.")

这使用 * and **语法来获取所有参数和关键字参数，然后使用 super使用这些参数调用父类(super class) __init__。

替代方案(更多工作)是:

def __init__(self, image, x, y):
    super().__init__(image=image, x=x, y=y)
    """A test!"""
    print("Test.")