Python导入全局变量比导入局部变量快?

因此,我和朋友们一起在Pygame中制作了一个游戏,我刚刚开始为主角编写动画。

我想有几种方法可以做到这一点。或者制作一个图像列表并在列表上循环,或者制作一个包含精灵表上图片坐标的字典。

我选择了第二个选项,现在我决定检查哪一个更快。所以我以一种非常简单的方式对它们进行编程,只是为了快速检查它们的性能。

结果非常接近(字典为0.41,没有字典为0.40)。然后我决定,我想试试如果我选择第一个选项,除了打电话 pygame.image.load 在单独的文件中,并将动画帧存储为全局变量,然后将其导入主文件。

我想它会很慢,因为我在某处读到python导入速度非常慢。。。但令人惊讶的是,我得到了0.021秒的结果!

这对性能来说是一个巨大的变化,这可能对我的游戏至关重要,所以我想知道是否有人会碰巧知道为什么这种方法速度如此之快,并且仅仅是因为某些x或y,为什么在这种情况下速度更快,而在另一种情况下速度会非常慢。

下面是与我的游戏当前状态类似的代码:

    import pygame
import time
start_time = time.time()
playerSpriteSize = 192
img = (0, 0)
class SpriteSheet():
    def __init__(self, filename):
        self.sheet = pygame.image.load(filename).convert()

    def get_image(self, coords, size, flip=False):
        surf = pygame.Surface(size).convert()
        surf.blit(self.sheet, (0, 0), (coords[0], coords[1], size[0], size[1]))
        pygame.transform.flip(surf, False, True)
        surf.set_colorkey((0, 0, 0))
        surf = pygame.transform.flip(surf, flip, False)
        return surf

pygame.init()

displaySurface = pygame.display.set_mode((400, 400))
x = SpriteSheet("playerAnimation.png")


animationList = {0: (0, playerSpriteSize*0), 1: (0, playerSpriteSize*1), 2: (0, playerSpriteSize*2),
                 3: (0, playerSpriteSize*3), 4: (0, playerSpriteSize*4), 5: (0, playerSpriteSize*5),
                 6: (0, playerSpriteSize*6)}
rounda = 0
for i in animationList:
    a1 = x.get_image(animationList[rounda], (playerSpriteSize, playerSpriteSize))
    displaySurface.blit(a1, (30, 30))
    rounda += 1
    pygame.display.update()


print("--- %s seconds ---" %(time.time() - start_time))

现在,这是使用在主游戏循环之前加载的图像的代码:

import pygame
import time
start_time = time.time()
imageSize = 192
img = (0, 0)
class SpriteSheet():
    def __init__(self, filename):
        self.sheet = pygame.image.load(filename).convert()

    def get_image(self, coords, size, flip=False):
        surf = pygame.Surface(size).convert()
        surf.blit(self.sheet, (0, 0), (coords[0], coords[1], size[0], size[1]))
        pygame.transform.flip(surf, False, True)
        surf.set_colorkey((0, 0, 0))
        surf = pygame.transform.flip(surf, flip, False)
        return surf

pygame.init()

displaySurface = pygame.display.set_mode((400, 400))
x = SpriteSheet("playerAnimation.png")

a1 = x.get_image((0, 0), (imageSize, imageSize))
a2 = x.get_image((0, 192), (imageSize, imageSize))
a3 = x.get_image((0, 384), (imageSize, imageSize))
a4 = x.get_image((0, 576), (imageSize, imageSize))
a5 = x.get_image((0, 768), (imageSize, imageSize))
a6 = x.get_image((0, 960), (imageSize, imageSize))
a7 = x.get_image((0, 1152), (imageSize, imageSize))

animationList = [a1, a2, a3, a4, a5, a6, a7]

for i in animationList:
    displaySurface.blit(i, (30, 30))
    pygame.display.update()

print("--- %s seconds ---" %(time.time() - start_time))

这是代码(分为2个文件),运行时间约为0.021秒: 文件1(主文件)

import pygame
import time
from mainDifferentExtern import a1, a2, a3, a4, a5, a6, a7


start_time = time.time()
imageSize = 192
img = (0, 0)
class SpriteSheet():
    def __init__(self, filename):
        self.sheet = pygame.image.load(filename).convert()

    def get_image(self, coords, size, flip=False):
        surf = pygame.Surface(size).convert()
        surf.blit(self.sheet, (0, 0), (coords[0], coords[1], size[0], size[1]))
        pygame.transform.flip(surf, False, True)
        surf.set_colorkey((0, 0, 0))
        surf = pygame.transform.flip(surf, flip, False)
        return surf

pygame.init()

displaySurface = pygame.display.set_mode((400, 400))
x = SpriteSheet("playerAnimation.png")

animationList = [a1, a2, a3, a4, a5, a6, a7]

for i in animationList:
    displaySurface.blit(i, (30, 30))
    pygame.display.update()

print("--- %s seconds ---" %(time.time() - start_time))

以及从中导入的文件:

import pygame
imageSize = 192


class SpriteSheet():
    def __init__(self, filename):
        self.sheet = pygame.image.load(filename).convert()

    def get_image(self, coords, size, flip=False):
        surf = pygame.Surface(size).convert()
        surf.blit(self.sheet, (0, 0), (coords[0], coords[1], size[0], size[1]))
        pygame.transform.flip(surf, False, True)
        surf.set_colorkey((0, 0, 0))
        surf = pygame.transform.flip(surf, flip, False)
        return surf

pygame.init()
pygame.display.set_mode((1, 1))
x = SpriteSheet("playerAnimation.png")

a1 = x.get_image((0, 0), (imageSize, imageSize))
a2 = x.get_image((0, 192), (imageSize, imageSize))
a3 = x.get_image((0, 384), (imageSize, imageSize))
a4 = x.get_image((0, 576), (imageSize, imageSize))
a5 = x.get_image((0, 768), (imageSize, imageSize))
a6 = x.get_image((0, 960), (imageSize, imageSize))
a7 = x.get_image((0, 1152), (imageSize, imageSize))

编辑:根据match的建议,我改变了测量时间的方法,改为使用python评测(使用cProfile),但我得到的结果大致相同,只是前两种方法的时间稍微长一点