[Matplotlib-users] Problem : Combining mouse button events with pick events in a scatter plot

joh johtoldr at yahoo.gr
Wed Sep 9 02:12:50 CEST 2015

Hello everybody, 

I am trying to combine mouse button events with a pick event in scatter
plot. Different functionalities take place, based on the mouse button
pressed each time. I want each functionality to be triggered with a
combination of mouse buttons events and/or key press events. When the left
mouse button is pressed matplotlib's Lasso widget is called and with the
included points functionality 1 takes place. When Shift+LMB are pressed a
Lasso is drawn and functionality 2 takes place with the included points.
When Alt+LMB are pressed a Lasso is drawn and with the included points
functionality 3 takes place. Last, but not least, when I press the RMB a
pick event is triggered and the index of the selected point in the scatter
plot is given. 

Since I added the pick event, the aforementioned functionalities work
correctly until a pick event is triggered. When it is triggered it seems
that the canvas gets locked and I can not use any other functionality. I
don't get the index of the selected points and I do not get any errors. 


import logging 
import matplotlib 
from matplotlib.widgets import Lasso 
from matplotlib.colors import colorConverter 
from matplotlib.collections import RegularPolyCollection 
from matplotlib import path 
import numpy as np 
import matplotlib.pyplot as plt 
from numpy.random import rand 

logger = logging.getLogger() 

class Datum(object): 
      colorin = colorConverter.to_rgba('red') 
      colorShift = colorConverter.to_rgba('cyan') 
      colorCtrl = colorConverter.to_rgba('pink') 
      colorout = colorConverter.to_rgba('blue') 

      def __init__(self, x, y, include=False): 
         self.x = x 
         self.y = y 
         if include: 
            self.color = self.colorin 
            self.color = self.colorout 

class LassoManager(object): 
      def __init__(self, ax, data): 
         self.axes = ax 
         self.canvas = ax.figure.canvas 
         self.data = data 

         self.Nxy = len(data) 

         facecolors = [d.color for d in data] 
         self.xys = [(d.x, d.y) for d in data] 
         fig = ax.figure 
         self.collection = RegularPolyCollection(fig.dpi, 6,
sizes=(100,),facecolors=facecolors, offsets = self.xys, transOffset =


         self.pick=self.canvas.mpl_connect('pick_event', self.onpick) 
         self.cid = self.canvas.mpl_connect('button_press_event',
         self.keyPress = self.canvas.mpl_connect('key_press_event',
         self.keyRelease = self.canvas.mpl_connect('key_release_event',
         self.lasso = None 
         self.shiftKey = False 
         self.ctrlKey = False 

      def callback(self, verts): 
          logging.debug('in LassoManager.callback(). Shift: %s, Ctrl: %s' %
(self.shiftKey, self.ctrlKey)) 
          facecolors = self.collection.get_facecolors() 
          p = path.Path(verts) 
          ind = p.contains_points(self.xys) 
          for i in range(len(self.xys)): 
              if ind[i]: 
                 if self.shiftKey: 
                    facecolors[i] = Datum.colorShift 
                 elif self.ctrlKey: 
                    facecolors[i] = Datum.colorCtrl 
                    facecolors[i] = Datum.colorin 
                    print self.xys[i] 
                   facecolors[i] = Datum.colorout 

          del self.lasso 

      def onpress(self, event): 
           if self.canvas.widgetlock.locked(): return 
           if event.inaxes is None:    return 
           self.lasso = Lasso(event.inaxes, (event.xdata, event.ydata),
           # acquire a lock on the widget drawing 

      def onKeyPress(self, event): 
          logging.debug('in LassoManager.onKeyPress(). Event received: %s
(key: %s)' % (event, event.key)) 
          if event.key == 'alt': 
             self.ctrlKey = True 
          if event.key == 'shift': 
             self.shiftKey = True 

      def onKeyRelease(self, event): 
          logging.debug('in LassoManager.onKeyRelease(). Event received: %s
(key: %s)' % (event, event.key)) 
          if event.key == 'alt': 
             self.ctrlKey = False 
          if event.key == 'shift': 
             self.shiftKey = False 

      def onpick(self,event): 

          if event.mouseevent.button == 3: 

             index = event.ind 
             print('onpick3 scatter:', index) 

      if __name__ == '__main__': 

         data = [Datum(*xy) for xy in rand(100, 2)] 

         ax = plt.axes(xlim=(0,1), ylim=(0,1), autoscale_on=False) 
         lman = LassoManager(ax, data) 


------------------End of Code----------------------------- 

Any suggestions on what might be causing this malfunction? What am I doing

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