Calculate cpu usage on linux

cpu_percent.py

import time

def cpu_percent():
    tmp_total = 0
    tmp_idle = 0
    for i in range(10):
        cpu_data = !head -n1 /proc/stat
        user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice = cpu_data[0].split()[1:]
        diff_idle = int(idle) - tmp_idle
        total_cpu_boot = sum(map(int, [user, nice, system, idle, iowait, irq, softirq, steal]))
        diff_total = total_cpu_boot - tmp_total
        diff_usage = 1000 * (diff_total - diff_idle) / (diff_total + 5) / 10
        print diff_usage
        tmp_total = total_cpu_boot
        tmp_idle = int(idle)
        time.sleep(1)