cpu-usage.py

#!/usr/bin/env python3
from time import sleep

with open("/proc/stat", "r") as fh:
    last_total, last_busy = None, None
    while True:
        fh.seek(0)
        for line in fh:
            if line.startswith('cpu '):
                parts = list(map(int, line.split()[1:]))
                user, nice, system, idle, iowait, irq, *_ = parts
                total = user + nice + system + idle + iowait + irq
                busy = total - idle - iowait
                if last_total is not None and last_busy is not None:
                    diff_total = total - last_total
                    diff_busy = busy - last_busy
                    usage = diff_busy / diff_total
                    print('%7.3f%%' % (100 * usage))
                last_total, last_busy = total, busy
        sleep(1)