在时钟上每 5 分钟运行一次 python 脚本

Question

I'm busy with an python script on a raspberry pi for a rain gauge. The script need to count the tips of the bucket and write the total rain amount every 5 minutes to a csv file. The script does the writing now every 299.9 seconds but I want it to write every exact 5 minutes, for example: 14:00, 14:05, 14:10 and so on.

Is there anyone who could help me out?

Thanks in advance!

Answer 1

使用 cronjob，对于树莓派，使用 crontab https://www.raspberrypi.org/documentation/linux/usage/cron.md

Answer 2

You will find lots of helpful functions in the datetime module:

from datetime import datetime, timedelta

# Bootstrap by getting the most recent time that had minutes as a multiple of 5
time_now = datetime.utcnow()  # Or .now() for local time
prev_minute = time_now.minute - (time_now.minute % 5)
time_rounded = time_now.replace(minute=prev_minute, second=0, microsecond=0)

while True:
    # Wait until next 5 minute time
    time_rounded += timedelta(minutes=5)
    time_to_wait = (time_rounded - datetime.utcnow()).total_seconds()
    time.sleep(time_to_wait)

    # Now do whatever you want
    do_my_thing()

Note that when do_my_thing() is called it will actually be fractionally after the exact time in time_to_round , because obviously computers can't do work in precisely zero time. It's guaranteed not to wake up before that time though. If you want to refer to the "current time" in do_my_thing() , pass in the time_rounded variable so that you get neat timestamps in your log file.

In the code above I've deliberately recomputed time_to_wait each time, rather than just setting it to 5 minutes after the first time. That's so that the slight delay I just mentioned don't gradually snowball after you've been running the script for a long time.