导入类时未定义错误全局变量 [英] Error Global Variable not defined when importing class

问题描述

我正在尝试实现一个移动系统，让玩家向点击位置移动.但是我遇到了一些关于移动方法参数的问题.

I am trying to implement a movement system where the player move's towards the click position. But I have been running into some problems with the arguments of the movement method.

移动方法目前需要将所有变量作为参数:

The movement method currently needs to take all the variables as arguments:

此代码有效:

def move(self,event,mouse_pos, screen, background):
        if event.type == MOUSEBUTTONDOWN:
            if mouse_pos[1] > self.pos[1]:
                screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                self.speed = 1
                self.move_south() #moves player
            if mouse_pos[0] > self.pos[0]:
                screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                self.speed = 1
                self.move_east() #moves player
            screen.blit(self.image, self.pos) #draws player  

此代码不起作用:

def move(self,event):
        if event.type == MOUSEBUTTONDOWN:
            if mouse_pos[1] > self.pos[1]:
                screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                self.speed = 1
                self.move_south() #moves player
            if mouse_pos[0] > self.pos[0]:
                screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                self.speed = 1
                self.move_east() #moves player
            screen.blit(self.image, self.pos) #draws player   

全班代码:

import pygame, sys
from pygame.locals import *

class GameObject:
    def __init__(self, image, height, speed):
        self.speed = speed
        self.image = image
        self.pos = image.get_rect().move(0, height) #initial placement

    def move_south(self):
        self.pos = self.pos.move(0, self.speed)
        if self.pos.right > 600:
            self.pos.left = 0

    def move_east(self):
        self.pos = self.pos.move(self.speed , 0)
        if self.pos.right > 600:
            self.pos.left = 0

    def move(self,event,mouse_pos, screen, background):
            if event.type == MOUSEBUTTONDOWN:
                if mouse_pos[1] > self.pos[1]:
                    screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                    self.speed = 1
                    self.move_south() #moves player
                if mouse_pos[0] > self.pos[0]:
                    screen.blit(background, self.pos, self.pos) #erases players by bliting bg 
                    self.speed = 1
                    self.move_east() #moves player
                screen.blit(self.image, self.pos) #draws player      

主脚本代码:

import pygame, sys
from pygame.locals import *
from classes import *

screen = pygame.display.set_mode((640, 480))
#Importing Chars
player = pygame.image.load('green_hunter_small.png').convert()
#player.set_alpha(100) #makes whole player transparent
player.set_colorkey((0,0,0)) #sets background colour to transparent

ennemi =  pygame.image.load('red_hunter_small.png').convert()
ennemi.set_colorkey((0,0,0))

background = pygame.image.load('grass_map_640x640.png').convert()
screen.blit(background, (0, 0))
objects = []
mouse_pos = (320, 240)
objects.append(GameObject(player, 80, 0))
for x in range(2):      #create 2 objects
    o = GameObject(ennemi, x*40, 0)
    objects.append(o)
while True:
    for event in pygame.event.get(): #setting up quit
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == MOUSEBUTTONDOWN :
            mouse_pos = pygame.mouse.get_pos()
            print mouse_pos
            for o in objects:
                screen.blit(background, o.pos, o.pos) #erases players by bliting bg 
            for o in objects:
                o.move(event,mouse_pos,screen,background)
    pygame.display.update()
    pygame.time.delay(100)

我有两个问题:1) 如何减少我的方法的参数数量?2) 如何让我的播放器不断向点击位置移动，而不是每次点击一次?

I've got two questions : 1) how to reduce the number of arguments for my method ? 2) how to get my player to move continually towards the click position rather than once at every click ?

推荐答案

你的问题是 python 中的全局"变量实际上并不是全局的，而是定义它们的模块的局部变量.因此，你不能引用classes.py 文件中的 main.py 文件中的全局变量.

Your problem is that "global" variables in python are not actually global, but rather local to the module in which they were defined in. Thus, you cannot reference globals decalred in the main.py file in the classes.py file.

有三种可能的解决方案:

There are three possible solutions:

1. (不推荐)将 screen 和 background 的声明移动到 classes.py 文件中，这会使它们看起来像不合适.

1. (not recomended) Move the declarations of screen and background to the classes.py file, which would put them seemingly out of place.

(也不推荐)在 classes.py 文件中添加一个 from main import screen, background，这会产生循环导入问题，迫使 main.py 模块执行它的 from classes import * after 定义 screen 和 background

(also not recommended) Add a from main import screen, background to the classes.py file, which creates circular import problems, forcing the main.py module to do its from classes import * after defining screen and background

mouse_pos 变量是完全没有必要和误用的:

The mouse_pos variable is totally unnecessary and misused:

1. 您可以直接在 classes.py 文件中使用 pygame.mouse.get_pos()，但是
2. 使用 pygame.mouse.get_pos() 本身是多余的，因为 pygame.MOUSEBUTTONDOWN 事件有一个 pos 属性指向触发事件时的鼠标.

1. You could just use pygame.mouse.get_pos() directly in the classes.py file, but
2. Using pygame.mouse.get_pos() itself is extranious because pygame.MOUSEBUTTONDOWN events have a pos attribute pointing to the position of the mouse when the event was fired.

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