绘制一个进程的CPU使用率

感谢Vamei的matplotlib 的文章：
http://www.cnblogs.com/vamei/archive/2013/01/30/2879700.html

代码如下：
首先用psutil 获得进程的CPU 使用率，然后再用matplotlib绘图。

import psutil
import sys
import re
ll=[]
def processinfo(pid):
    p=psutil.Process(pid)
    for i in range(10):
        #print(p.cpu_percent(interval=3))
        ll.append(p.cpu_percent(interval=1))
    return ll


#print(processinfo(1051))
import random
from matplotlib.figure import Figure
from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
def plot_cpu_usage(y):
    x=list(range(3,31,3)) #x
    #I will manipulate Y if ll is empty
    if not y:
        y=[random.randint(1,5) for i in range(10)] #y

    fig = Figure()
    canvas = FigureCanvas(fig)
    ax = fig.add_axes([0.1, 0.1, 0.8, 0.8])
    line, = ax.plot(x,y)
    ax.set_title("cpu usage for PID 1051")
    ax.set_xlabel(" time in seconds  ")
    ax.set_ylabel(" cpu usage in %")
    canvas.print_figure('demo.jpg')

#processinfo(1051)
plot_cpu_usage(ll)

另外我发现3.5的python 跟matplotlib 配合使用的时候，无法使用GTKAgg 作为backend. 

#next 5 lines error out on Kali linux with python3.5, but works with python2.7
import matplotlib as mpl
mpl.use('GTKAgg')        #use GTK UI
mpl.use('GTKCairo')
import matplotlib.pyplot as plt
plt.plot([1,3,2,4])
plt.show()

但是我可以正常的import Gtk 

python3
import gi
gi.require_version('Gtk','3.0')
from gi.repository import Gtk as gtk