Question

我一直在按照教程向初学者展示如何制作太空侵略者＆＃34;游戏。我大多只想要一种方法来玩龟图形或类似的东西。一切都进展顺利，直到我注意到我的if语句，我在我定义我的move_left函数时创建，不起作用。然而问题不在于if语句本身。我试图在它下面做的任何数学运算都被程序完全忽略，没有错误信息或任何东西。我甚至试图在if语句下做一个print语句，只是为了看到实际的语句是否有响应，并且确实看到了我按计划打印的语句。什么给出了什么？为什么我不能在这两个函数下做任何数学方程式或类似的东西？

所以，这是我在下面遵循的代码：

import turtle
import os

def main():
    #Set up the screen

    wn = turtle.Screen()
    wn.bgcolor("black")
    wn.title("Space Invaders")

    #Draw Border
    border_pen = turtle.Turtle()
    border_pen.speed(0)
    border_pen.color("white")
    border_pen.penup()
    border_pen.setposition(-300, -300)
    border_pen.pendown()
    border_pen.pensize(3)

    for side in range (4):
        border_pen.fd(600)
        border_pen.lt(90)
    border_pen.hideturtle()

    #create the player turtle

    player = turtle.Turtle()
    player.color("blue")
    player.shape('triangle')
    player.penup()
    player.speed(0)
    player.setposition(0, -250)
    player.setheading(90)


    #Player controls

    playerspeed = 15

    def move_left():
        x = player.xcor()
        x -= playerspeed
        player.setx(x)
        print(x)
        if x < -280:
            print("Reached") #It is here I tested rather or not the if statement 
                             #above works, which it does
            x = -280 #The following code here will not take effect. I tried all
                     #of different signs to use. Nothing happens. Not even an 
                     #error

    def move_right(): #I did not put the if statement here since I noticed the
                      #problem with the left side first
        x = player.xcor()
        x += playerspeed
        player.setx(x)
        if x > 280:
            x = 280

    turtle.listen()
    turtle.onkey(move_left, "Left")
    turtle.onkey(move_right, "Right")

    turtle.mainloop()

main()

Answer 1

代码没有影响的原因是因为你修改了x的值，一个局部变量到函数范围，而不是玩家位置。更新本地变量player.setx(x)后，调用x实际更新玩家位置。如果您想绑定您的位置，您还可以使用内置的min / max方法：

   def move_left():
        x = player.xcor()
        x -= playerspeed
        player.setx(max(x, -280))

    def move_right():
        x = player.xcor()
        x += playerspeed
        player.setx(min(x, 280))

Python：数学运算符怎么会起作用？

1 个答案: