m and z crashes

main.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.graphics import Color, Ellipse, Line
from kivy.uix.boxlayout import BoxLayout
from kivy.core.window import Window
from kivy.interactive import InteractiveLauncher
from kivy.properties import NumericProperty
from kivy.event import EventDispatcher


import random

framePoints = [150, 250, 750, 250, 750, 600, 150, 600, 150, 250]
CIRCLEPOSITIONS = ([200,300],[350,300],[500,300],[650,300],[200,400],[350,400],[500,400],[650,400],[200,500],[350,500],[500,500],[650,500])
CIRCLESIZE = 80

RED = (0.3,0.3,0.3)
BLUE = (.6, .8, .6)
WHITE = (1,1,1)

NTRIALS = 12

itemGroups = {'YN': [[['T','TICK'],['T','POCK'],['Z','TICK'],['Z','POCK'],['M','TICK'],['M','POCK']],[['T','TICK'],['T','POCK'],['Z','TICK'],['Z','POCK'],['M','TICK'],['M','POCK']]]}


class Circles:

    def __init__(self, posx, posy, color):
        self.x = posx
        self.y = posy
        self.col = color
			
			
class Configuration:

    def __init__(self, nred = 6, nblue = 6):
        self.nred = nred
        self.nblue = nblue
        self.circles = []
        self.setupConf()
						
    def setupConf(self):
	
        circlePosz = list(CIRCLEPOSITIONS)
			
        for i in range(0,self.nred):
            coord = circlePosz.pop(0)
            self.circles.append(Circles(coord[0],coord[1],RED))
			
        for i in range(0,self.nblue):
            coord = circlePosz.pop(0)
            self.circles.append(Circles(coord[0],coord[1],BLUE))

class Trials:
		
    def __init__(self):
        self.setup = None
        self.question = None 
        self.ans = None 
        self.time = None 

    def evaluate (self, answer):
        return True
				
				

class Session(Widget):

    trialDisplayed = NumericProperty(0)


    def __init__(self, tyype, number):
        self.tyype = tyype
        self.number = number
        self.trials = []
        self.makeSession()
							
    def makeSession(self):
			
        for group in itemGroups[self.tyype]:
					
            random.shuffle(group)
            for tr in group:
									
                if tr[0] == 'T': nred = 12
                if tr[0] == 'Z': nred = 0
                if tr[0] == 'M': nred = random.randint(4,8)
									
                thisTrial = Trials()
                thisTrial.setup = Configuration(nred,12-nred)
                thisTrial.question = tr[1]
                self.trials.append(thisTrial)				


# here I'm trying defining trialDisplayed as a Numeric Property

	
    
# here I'm trying to define on_key_down as a keyboard listener (but it doesn't listen :/ )
    



							
					
#					if self.tyype == 'YN':
					
#					if self.tyype == 'COMPARISON':
					
					


class DisplayWidget(Widget):
	
  			
    def __init__(self, frame, setup, **kwargs):
        super(DisplayWidget, self).__init__(**kwargs)
#        Window.clearcolor = (0.1, 0.1, 0.1, 1.)


        with self.canvas:
        
            Color(*WHITE)
            Line(points=frame, width=2.5)           
                                                    
            for circle in setup.circles:            
                Color(*circle.col)
                d = CIRCLESIZE
                Ellipse(pos=(circle.x , circle.y), size=(d, d))


	

class TiktokApp(App):


    def build(self):		
		
        Window.bind(on_key_down=self.on_key_down)

        session = Session('YN',1)
        layout = BoxLayout(orientation='vertical')
        

#      here I want to put the trialDisplayed instead of the [0] to select the right Trials object in session.trials        

        display = DisplayWidget(framePoints, session.trials[session.trialDisplayed].setup)
        text = Label(text=session.trials[session.trialDisplayed].question + ' cercles sont rouges')
        layout.add_widget(display)
        layout.add_widget(text)
                      
        return layout

    def build_config(self, config):
        config.setdefaults('graphics', {
            'width': '1280',
            'height': '1024'
        })
        
    def on_key_down(self, keycode, *args):
        print args[2]
        if args[2] in ['m','y']: 
            session.trialDisplayed += 1
            print 'yayyy'		
#            print session.trialDisplayed	
        



if __name__ == '__main__':
    TiktokApp().run()