This is very simple, rough code, but it does soemthing I have anted to accomplish for a very long time! I did this Jun22,2016.

 

See the codes in:   /home/sco/sco/codes/python/cursor

% cat a.1

# data 
1.0 2.0 
2.0 3.0 
3.0 5.0
4.0  8.0 

% cat cursor6.py
from scomods.ascii_tools import *
import matplotlib.pyplot as plt 
import numpy as np 

x = read1col('1','a.1')
y = read1col('2','a.1')

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(x,y,'ro')
plt.axis([-1.0, 12.0, -1.0, 12.0])

def onclick(event):
    print('button=%d, x=%d, y=%d, xdata=%f, ydata=%f' %
          (event.button, event.x, event.y, event.xdata, event.ydata))
    if event.button == 3:
     plt.close()  

cid = fig.canvas.mpl_connect('button_press_event', onclick)

plt.show()

To run:
% python cursor6.py