问题描述

def getMove(win,playerX,playerY):

    #Define variables.
    movePos = 75
    moveNeg = -75
    running = 1

    #Run while loop constantly to update mouse's coordinates.
    while(running):

        mouseCoord = win.getMouse()
        mouseX = mouseCoord.getX()
        mouseY = mouseCoord.getY()
        print "Mouse X = ", mouseX
        print "Mouse Y = ", mouseY

        if mouseX >= playerX:
            playerX = movePos + playerX
            running = 0
        elif mouseX <= playerX:
            playerX = moveNeg + playerX           
            running = 0
        elif mouseY >= playerY:
            playerY = movePos + playerY            
            running = 0
        elif mouseY <= playerY:
            playerY = moveNeg + playerY            
            running = 0
    return playerX,playerY

def main():

    #Create game window.
    win = GraphWin("Python Game", 500, 500)
    drawBoard(win)

    #Define variables.
    playerX = 75
    playerY = 125
    keyX = 325
    keyY = 375
    running = 1


    #Create Key and Player objects, draw the key, but don't draw the player yet.
    key = Text(Point(keyX,keyY),"KEY")
    key.draw(win)

    while(running):
        print "player X = ", playerX
        print "Player Y = ", playerY
        drawBoard(win)
        getMove(win,playerX,playerY)
        player = Circle(Point(playerX,playerY),22)
        player.setFill('yellow')
        player.draw(win)
main()

我正在使用图形库来创建游戏.我的播放器和钥匙被绘制在正确的位置.但是，当调用 getMove 函数时，我的 playerX 和 playerY 没有更新.我添加了调试打印语句以在运行游戏时找到它们的值，它始终是 75 和 125.求助！

I am using a graphics library to create a game. My player and key are drawn in the correct places. However, when calling the getMove function, my playerX and playerY do not update. I have added debug print statements to find their values while running the game and it is always 75 and 125. Help!

推荐答案

在python中，整数是不可变的——当你给一个变量分配一个新的整数值时，你只是让变量指向一个新的整数，而不是改变什么它指向的旧整数的值是.

In python, integers are immutable - when you assign a new integer value to a variable, you are just making the variable point to a new integer, not changing what the old integer it pointed to's value was.

(python 中可变对象的一个​​示例是列表，您可以对其进行修改，并且指向该列表的所有变量都会注意到更改 - 因为 LIST 已更改.)

(An example of a mutable object in python is the list, which you can modify and all variables pointing to that list will notice the change - since the LIST has changed.)

同样，当您将变量传递给 python 中的方法，然后更改该变量在该方法中指向的内容时，您不会更改该变量指向该方法之外的内容，因为它是一个新变量.

Similarly, when you pass a variable into a method in python and then alter what the variable points to in that method, you do not alter what the variable points to outside of that method because it is a new variable.

为了解决这个问题，将返回的 playerX,playerY 分配给方法外的变量:

To fix this, assigned the returned playerX,playerY to your variables outside the method:

playerX, playerY = getMove(win,playerX,playerY)

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