import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)
ax.set_title('click on points')
# 设置绘图元素的picker属性启用对象拾取事件
line, = ax.plot(np.random.rand(10)*10, 'o', picker=5)
ax.axis([0,10,0,10])

def onpick(event):
  # 通过event.artist属性获取被拾取到的数据元素
  thisline = event.artist
  # 获取数据元素的x,y坐标数组
  xdata = thisline.get_xdata()
  ydata = thisline.get_ydata()
  # 获取到当前元素的索引
  ind = event.ind
  # xdata[ind]为当前元素的x坐标，ydata[ind]为当前元素的y坐标。
  ax.plot((0,xdata[ind]), (ydata[ind],ydata[ind]), 'g--')
  ax.plot((xdata[ind],xdata[ind]), (0,ydata[ind]), 'g--')
  # 重绘图像
  thisline.figure.canvas.draw()
# 绑定事件
fig.canvas.mpl_connect('pick_event', onpick)

plt.show()