Question

我最近开始使用python编程，到目前为止我喜欢它。我以前用c＃和java编程，这可能导致我的问题。在c＃中，如果你有一个公共变量，它将在每个方法中改变。很抱歉这个错误的解释，但是可视化代码会更容易。

这段代码是我希望在c＃form中以python发生的一个例子。代码实际上并不起作用，因为它只是一个例子。

class Player
{
    public var player; //create the variable
    public var playerRectangle;
    public var playerMovement;

    public Player()
    {
        player = pygame.image.load("player.png"); //set the variables value
        playerRectangle = player.get_rect();

        playerMovement = new int[0,0];
    }

    public void Update()
    {
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN and event.key == pygame.K_w:
                playerMovement[1] = -2   //use the variables value
            if event.type == pygame.KEYDOWN and event.key == pygame.K_s:
                playerMovement[1] = 2
            if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
                playerMovement[0] = -2
            if event.type == pygame.KEYDOWN and event.key == pygame.K_d:
                playerMovement[0] = 2

            if event.type == pygame.KEYUP and event.key == pygame.K_w:
                playerMovement[1] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_s:
                playerMovement[1] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_a:
                playerMovement[0] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_d:
                playerMovement[0] = 0

        playerRectangle = playerRectangle.move(playerMovement)
    }
}

实际的python代码是：

import pygame

class Player:
    player = None #create the variable
    playerRectangle = None
    playerMovement = None

    def __init__():
        global player
        player = pygame.image.load("player.png") #set the variables value
        global playerRectangle
        playerRectangle = player.get_rect()

        global playerMovement
        playerMovement = [0,0]

    def update():
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN and event.key == pygame.K_w:
                playerMovement[1] = -2 #use the variables !!ERROR!!
            if event.type == pygame.KEYDOWN and event.key == pygame.K_s:
                playerMovement[1] = 2
            if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
                playerMovement[0] = -2
            if event.type == pygame.KEYDOWN and event.key == pygame.K_d:
                playerMovement[0] = 2

            if event.type == pygame.KEYUP and event.key == pygame.K_w:
                playerMovement[1] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_s:
                playerMovement[1] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_a:
                playerMovement[0] = 0
            if event.type == pygame.KEYUP and event.key == pygame.K_d:
                playerMovement[0] = 0

        playerRectangle = playerRectangle.move(playerMovement)

    def returnTexture():
        return player

    def returnRectangle():
        return playerRectangle

它表示变量在给定值之前被引用，但我在构造函数中给它一个值。

Answer 1

您已忘记（或未阅读）在您的方法中使用self。

您需要将self放在方法定义中并使用self.<attribute>引用实例上的属性。

示例：

class Player(object): def __init__(self, name): self.name = name def update_name(self, name): self.name = name bob = Player("Bob") print bob.name # Bob bob.update_name("Bob Jones") print bob.name # Bob Jones

注意：在Python中类的方法定义中使用self只是按惯例;您可以使用您喜欢的任何名称，但我们广泛而且通常（按惯例）使用self。

请参阅：Classes

另请参阅：What is the purpose of self?

旁注：其中一个原因（ btw ）是在Python中我们希望更清楚地了解如何编写代码。请参阅Zen of Python
的第二行

Zen of Python

Beautiful is better than ugly. Explicit is better than implicit. ...

更新：它也没有价值（请阅读文档），没有公共与私人成员使用Python的概念类型系统。我们定义＆＃34;私人＆＃34;按惯例，成员通常只带有带前缀的单下划线;例如：def _foo(self):作为私人/ inernal方法。

在赋值之前引用的Python全局变量

1 个答案: