使用pygame时如何在python中处理时间

Question

我正在做一个模拟，它代表一条带有移动产品的生产线。

我对纸上某个 (x,y) 的产品到达时间的计算与我的模拟计算不匹配。

我的 pygame while 循环的迭代时间为 0.01 秒，不确定性非常小。

所以我的像素移动为 0.5，长度为例如 645 像素。 所以我认为每一步都是 0.5 像素，总共需要 1290 步。迭代时间为 0.01 秒，这应该有 12.9 秒的持续时间。

但是，对于 645 像素的长度，我的模拟需要 16 秒。

有人能解释一下区别吗？

我用一个 RECT 做了一段代码，所以迭代时间比较快但是还是有区别的

示例：

import pygame, sys, time, random
init_time = time.time()
from pygame.locals import *



pygame.init()

w_x = 1550
w_y = 800

DISPLAYSURF = pygame.display.set_mode((w_x,w_y))
pygame.display.set_caption('COPAL')

## COLORS USED (SIZE CORRESPONDS TO COLOR)
# background
BLACK = (0,0,0)

# boxes
GREEN = (0,100,0)
PINK = (255,0,255)
BLUE = (0,0,128)

xx = 0
yy = 400

but_on = True
sum_duration = 0
total_iteration = 0

total = []



box = [[xx,yy]]

## Filling background
DISPLAYSURF.fill(BLACK)
start = time.time()

start2 = time.time()


while True:


    init_end = time.time()


    if but_on == True:
        print(init_end-init_time)
        but_on = False    


    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()



    DISPLAYSURF.fill(BLACK)

    pygame.draw.rect(DISPLAYSURF,BLUE,(xx,yy,30,30))


    pygame.draw.line(DISPLAYSURF,PINK,(645,0),(645,800))

    xx += 0.5

    if xx == 645:

        timex = time.time()
        print(timex - start2)

        print(time_iteration_avg)


    stop = time.time()

    duration = stop - init_end

    total.append(duration)

    sum_duration += duration

    time_iteration_avg = sum_duration / len ( total )




   pygame.display.update()

示例编辑

import pygame, sys, time, random
init_time = time.time()
from pygame.locals import *



pygame.init()

# window aize
w_x = 1550
w_y = 800

# time for each step
ite = 0.00387

DISPLAYSURF = pygame.display.set_mode((w_x,w_y))
pygame.display.set_caption('COPAL')


# background
BLACK = (0,0,0)

# boxes
GREEN = (0,100,0)
PINK = (255,0,255)
BLUE = (0,0,128)

# start position
xx = 0
yy = 400

but_on = True
sum_duration = 0
total_iteration = 0

total = []

oo= 0

step = 0.5

duration = ite

box = [[xx,yy]]

## Filling background
DISPLAYSURF.fill(BLACK)
start = time.time()

start2 = time.time()


while True:


    init_end = time.time()


    if but_on == True:
        init_t = (init_end - init_time)

        print(init_t)
        but_on = False    


    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()



    DISPLAYSURF.fill(BLACK)

    pygame.draw.rect(DISPLAYSURF,BLUE,(xx,yy,30,30))


    pygame.draw.line(DISPLAYSURF,PINK,(645,0),(645,800))

    xx += step

    if round(xx) == 645:

        timex = time.time()
        print("elapsed time ")
        print(timex - start2)

        print(time_iteration_avg)




    if duration == ite:

        step = 0.5



    if duration < ite:
        dif_ite = ite - duration
        time.sleep(dif_ite)

        print("Smaller")

        step = 0.5

    if duration > ite:
        dif_pix = duration - ite

        pix_ex = 5 / duration

        step = 645 / pix_ex

        print("Bigger")

    total.append(duration)

    sum_duration += duration

    time_iteration_avg = sum_duration / len ( total )


    print(step)


    stop = time.time()
    duration = stop - init_end


    pygame.display.update()

Answer 1

Jammy Dodger 已经指出了主要问题，但我会尝试进一步解释。
当您编写游戏（或任何物理模拟）时，您不能依赖于您的代码片段将始终花费相同的时间来执行这一事实。有可能：
1- 您尝试挂起您的应用程序（通过睡眠），但操作系统可能无法在您指定的确切时间恢复程序的执行。我会说这是主要原因。
2- 您尝试在屏幕/GPU/RAMbuffer 上绘制一些东西，设备的工作速度可能因您的每个请求而异。
3- 可能还有几十个我现在想不出来的原因。

正确的做法是测量帧之间经过的时间量，并相应地调整您的物理模拟（例如：代码中框的速度）。阅读 xx += ... 部分附近的 cmets。 （有些人可能会因为使用time.sleep而不是pygame的clock.tick而批评代码，但我只是想让它易于理解）：

import pygame, sys, time, random
init_time = time.time()
from pygame.locals import *


#  frame per second you want
FPS = 100

#  speed at each frame
SPEED = 0.5

#  use a pygame clock object to control FPS
#clock = pygame.time.Clock()





pygame.init()

w_x = 1550
w_y = 800

DISPLAYSURF = pygame.display.set_mode((w_x,w_y))
pygame.display.set_caption('COPAL')

## COLORS USED (SIZE CORRESPONDS TO COLOR)
# background
BLACK = (0,0,0)

# boxes
GREEN = (0,100,0)
PINK = (255,0,255)
BLUE = (0,0,128)

xx = 0
yy = 400

but_on = True
sum_duration = 0
total_iteration = 0

total = []



box = [[xx,yy]]

## Filling background
DISPLAYSURF.fill(BLACK)
start = time.time()

start2 = time.time()


#  initial value
time_spend_py = 1 / FPS

elapsed_step = 0
while True:
    init_end = time.time()
    loop_start_time = time.time()

    if but_on == True:
        print(init_end-init_time)
        but_on = False    

    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    DISPLAYSURF.fill(BLACK)

    pygame.draw.rect(DISPLAYSURF,BLUE,(xx,yy,30,30))


    pygame.draw.line(DISPLAYSURF,PINK,(645,0),(645,800))


    #  amount of change depends on elapsed time since last frame!
    #  Example:
    #  FPS: 100, time_spend=0.012 s
    #  your loop took more time at last iteration
    #  because of that we need to adjust speed
    #  xx += SPEED * (0.012 / (1/100))
    #  xx += SPEED * (0.012 / 0.010)
    #  xx += SPEED * 1.2
    #  so object moves faster
    xx += SPEED * (time_spend_py / (1 / FPS))    

    if xx >= 645:

        timex = time.time()
        print(timex - start2)

        print(time_iteration_avg)
        print("Elapsed step:{}".format(elapsed_step))
        exit(0)


    pygame.display.update()

    stop = time.time()
    duration = stop - init_end
    total.append(duration)
    sum_duration += duration
    time_iteration_avg = sum_duration / len ( total )

    #time_spend = clock.tick(FPS)
    time.sleep(0.01)
    elapsed_step += 1
    loop_end_time = time.time()
    time_spend_py = loop_end_time - loop_start_time