Matplotlib制作交互式驻波动画

最近学写了matplotlib的动画的制作，于是就用FuncAnimation作了这个小程序，暂停部分还有问题，希望大家能帮忙解决下

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import Button
import matplotlib.animation as animation

#振幅、波长、角速度
A = 0.5
lm = 1
global w
w = 1
#暂停标志位,last_time用于存储上一个时间
pause = False
last_time = 0

#创建两个实例，fig用于返回图像,ax用于绘制动画,可能理解有出入
fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.2)
#创建fig返回的初始图像
x = np.arange(0, 2*np.pi, 0.01)
line, = ax.plot(x, 2*A*np.cos(2*np.pi*x/lm)*np.cos(w*0))
line2, = ax.plot(x, A*np.cos(w*0-2*np.pi*x/lm))
line3, = ax.plot(x, A*np.cos(w*0+2*np.pi*x/lm))

def zhubo(i):
    if pause:
        global last_time
        i = last_time
        return line,line2,line3
    line.set_ydata(2*A*np.cos(2*np.pi*x/lm)*np.cos(w*i))
    line2.set_ydata(A*np.cos(w* i-2*np.pi*x/lm))
    line2.set_color('g')
    line3.set_ydata(A*np.cos(w*i+2*np.pi*x/lm))
    line3.set_color('r')
    last_time = i
    w_text = ax.text(0.05, 0.9, 'Stop', transform=ax.transAxes)
    w_text.set_text('w = '+str(w))
    return line,line2,line3,w_text


# init一下清理屏幕
def init():
    line.set_ydata(np.ma.array(x, mask=True))
    line2.set_ydata(np.ma.array(x, mask=True))
    line3.set_ydata(np.ma.array(x, mask=True))
    return line,
    

class Index(object):
    ind = 0
#暂停
    def stop(self, event):
        global pause
        pause ^= True
#减小w
    def redu(self, event):
        global w
        w -= 1
#增加w
    def incr(self, event):
        global w
        w += 1

callback = Index()
#参数：每一帧返回的图像实例，绘制每一帧的函数，动画长度，
#       是否启用一个函数来刷新，如果不设置则用第二个参数的第一帧刷新
#       帧率？貌似是
#       是否刷新所有的点
zb = animation.FuncAnimation(fig, zhubo, np.arange(1,10,0.1), init_func=init,
                              interval=50, blit=True)

#设置三个功能按钮，并绑定槽函数
axincr = plt.axes([0.39, 0.05, 0.2, 0.075])
axredu = plt.axes([0.6, 0.05, 0.2, 0.075])
axstop = plt.axes([0.81, 0.05, 0.1, 0.075])

bstop = Button(axstop, 'Stop')
bstop.on_clicked(callback.stop)

bredu = Button(axredu, 'Reduce the cycle')
bredu.on_clicked(callback.redu)

bincr = Button(axincr, 'Increase the cycle')
bincr.on_clicked(callback.incr)
#zb.save('111.html')
plt.show()