python 如何在精准的时间间隔执行

比如这段：

import sched, time
import datetime

def whileOneSecond():
    while True:
        print(datetime.datetime.now())
        time.sleep(1)

whileOneSecond()

import sched, time

import datetime

def whileOneSecond():

while True:

print(datetime.datetime.now())

time.sleep(1)

whileOneSecond()

输出结果为：

2019-05-15 13:07:10.188710
2019-05-15 13:07:11.188965
2019-05-15 13:07:12.189855
2019-05-15 13:07:13.190381
2019-05-15 13:07:14.190849
2019-05-15 13:07:15.191828
2019-05-15 13:07:16.192440
2019-05-15 13:07:17.193014
2019-05-15 13:07:18.193326
2019-05-15 13:07:19.193606
2019-05-15 13:07:20.194679
2019-05-15 13:07:21.195403
2019-05-15 13:07:22.195706
2019-05-15 13:07:23.195851
2019-05-15 13:07:24.196235
2019-05-15 13:07:25.196626
2019-05-15 13:07:26.197574
2019-05-15 13:07:27.197850
2019-05-15 13:07:28.198161
2019-05-15 13:07:29.198770
2019-05-15 13:07:30.199328
2019-05-15 13:07:31.199998

2019-05-15 13:07:10.188710

2019-05-15 13:07:11.188965

2019-05-15 13:07:12.189855

2019-05-15 13:07:13.190381

2019-05-15 13:07:14.190849

2019-05-15 13:07:15.191828

2019-05-15 13:07:16.192440

2019-05-15 13:07:17.193014

2019-05-15 13:07:18.193326

2019-05-15 13:07:19.193606

2019-05-15 13:07:20.194679

2019-05-15 13:07:21.195403

2019-05-15 13:07:22.195706

2019-05-15 13:07:23.195851

2019-05-15 13:07:24.196235

2019-05-15 13:07:25.196626

2019-05-15 13:07:26.197574

2019-05-15 13:07:27.197850

2019-05-15 13:07:28.198161

2019-05-15 13:07:29.198770

2019-05-15 13:07:30.199328

2019-05-15 13:07:31.199998

这个一秒间隔算是准的，但这是因为程序中什么也没做

加入循环中有耗时大约为30 millisecond的代码，这里直接用 time.sleep(0.03)代替

import sched, time
import datetime

def whileOneSecond():
    while True:
        print(datetime.datetime.now())
        time.sleep(0.03)
        time.sleep(1)

whileOneSecond()

import sched, time

import datetime

def whileOneSecond():

while True:

print(datetime.datetime.now())

time.sleep(0.03)

time.sleep(1)

whileOneSecond()

这样的输出结果就和每一秒执行一次的最初设计越来越远

所以，要计算出程序执行所占用的时间，并在 sleep 里减去这个时间

代码如下

import sched, time
import datetime
import random

def whileOneSecond():
    startMillSecond = int(time.time() * 1000)
    while True:
        print(datetime.datetime.now())
        f= random.random()/10
        #print(f)
        time.sleep(f)
        millSeondDiff = int(time.time() * 1000) - startMillSecond
        #time.sleep(1)
        time.sleep((1000-millSeondDiff)/1000)
        startMillSecond = int(time.time() * 1000)


whileOneSecond()

import sched, time

import datetime

import random

def whileOneSecond():

startMillSecond = int(time.time() * 1000)

while True:

print(datetime.datetime.now())

f= random.random()/10

#print(f)

time.sleep(f)

millSeondDiff = int(time.time() * 1000) - startMillSecond

#time.sleep(1)

time.sleep((1000-millSeondDiff)/1000)

startMillSecond = int(time.time() * 1000)

whileOneSecond()