python - 在 python 中限制 Fps

Question

我希望我的程序每 x 帧执行一次任务。但是它似乎不起作用，因为 python 中的计时器似乎不准确。我如何让这段代码服从我设置的帧率？

import time
fps = 5
skipticks = 1/(fps*1.0)
i= 0
nextsnap=time.clock()
print skipticks, fps
while (True):
    tim= time.clock()
    i=i+1
    # this prints the fps
    #'print 'Fps at start',i, 1/(time.time()-tim)
    # this is the sleep that limits the fps
    nextsnap+=skipticks
    sleeptime = nextsnap-time.clock()
    if (sleeptime>0):
        time.sleep (sleeptime)
    else:
        print 'took too long'
    print 'Fps at end:#', i, 1/(time.clock()-tim)

这在我的电脑上产生:

 Fps at end:# 45 4.36627853079
Fps at end:# 46 6.44119324776
Fps at end:# 47 4.53966049676
Fps at end:# 48 4.66471670624
Fps at end:# 49 7.18312473536
Fps at end:# 50 4.34786490268
Fps at end:# 51 6.5263951487
Fps at end:# 52 4.71715853908
Fps at end:# 53 4.59636712435
Fps at end:# 54 6.87201830723
Fps at end:# 55 4.31062740848

为什么有些帧渲染的太快了？为什么 fps 计数不准确？

Answer 1

如果是关于测量 time.clock() 和 time.sleep() 的准确性，请使用尽可能简单的方法，例如:

import time

fps = 5
time_delta = 1./fps

while True:
    t0 = time.clock()
    time.sleep(time_delta)
    t1 = time.clock()
    print 1. / (t1 - t0)

您的操作系统是什么？这个简单措施的结果是什么？

如果是关于清理您的代码，我会更清楚地分开FPS 评估、处理 和 sleep 调用。这是一个示例(应忽略显示的循环 #0 频率)。

import time
import random
from itertools import count

fps = 5
loop_delta = 1./fps

current_time = target_time = time.clock()
for i in count():
    #### loop frequency evaluation
    previous_time, current_time = current_time, time.clock()
    time_delta = current_time - previous_time
    print 'loop #%d frequency: %s' % (i, 1. / time_delta)

    #### processing
    # processing example that sleeps a random time between 0 and loop_delta/2.
    time.sleep(random.uniform(0, loop_delta / 2.))

    #### sleep management
    target_time += loop_delta
    sleep_time = target_time - time.clock()
    if sleep_time > 0:
        time.sleep(sleep_time)
    else:
        print 'took too long'

此外，您可能需要 time.time() 而不是 time.clock()。参见 time.clock() vs. time.time() - accuracy回答。