Making a Tkinter button do something while the program is within a loop

Question

This is part of a longer program. All these methods are within the same class. What this program basically does is that whenever the start button is pressed the program runs within a 30 second loop. During these 30 seconds, every time a touch sensor is touched the mouse gets water for 2 seconds. There's also a 'GiveWater' button that allows the mouse to drink every time I press it.

I used tkinter to create the butttons

However, the button only works when the program is not within the 30 second loop. How can I can the 'GiveWater' button work even while the program is within the loop?

I know there's something about multi-threading but I'm new to python and I don't really know what it is or how it works.

I would greatly appreciate if anyone can explain in simple English how I can use multi-threading for this program or an alternative way to make this program work.

def createStartButton(self):
    """creates a button to start the program"""
    #Whenever button is pressed the 'touchSensor' method is invoked.
    self.StartButton = Button(self, text = 'Run touch sensor', command = self.touchSensor)        
    self.StartButton.grid()

def createGiveWaterButton(self):
    """creates a button that gives water to mouse whenever pressed"""
    #Whenever button is pressed the 'giveWater' method is invoked.
    self.WaterButton = Button(self, text = 'Give water', command = self.giveWater).        
    self.WaterButton.grid()

def giveWater(self):
    #Every time setOutputState(n, True) the output sends a signal..
    #..allowing the mouse to get water until it's set to False.
    self.myObject.setOutputState(0, True)
    time.sleep(0.1)
    self.myObject.setOutputState(0, False)

def touchSensor(self):
    """controls how the touch sensor runs"""

    time_at_program_start = time.time()

    #Every time setOutputState(n, True) it the output sends..
    #..a signal until it's set to False

    while True:
        self.myObject.setOutputState(0, False)

        #If the sensorValue > 900 (i.e. it's touched) the output is True       
        #(i.e. sends a signal allowing the mouse to drink.)
        if self.myObject.getSensorValue(2) >900:
            self.myObject.setOutputState(0, True)
            #waits 2 seconds
            time.sleep(2)
            #sets OutputState to False so the signal stops.
            self.myObject.setOutputState(0, False)

        #checks if the program already runs for 30 seconds.
        #If it does the loop/program stops.
        if time.time() - time_at_program_start >= 30:
            break

Don't use time.sleep() in tkinter applications. Use the after method instead. — TigerhawkT3
– TigerhawkT3, Commented Jul 10, 2015 at 17:06
sleep stops execution of the program for a certain amount of time. after puts a task on the application's "to-do list." — TigerhawkT3
– TigerhawkT3, Commented Jul 10, 2015 at 17:14

Noctis Skytower · Accepted Answer · 2015-07-10 17:54:05Z

2

Replace your touchSensor method with the following two methods and use them instead:

def touchSensor(self):
    self.after_idle(self.touchSensorLoop, time.time())

def touchSensorLoop(self, time_at_program_start):
    self.myObject.setOutputState(0, False)
    if time.time() - time_at_program_start < 30:
        if self.myObject.getSensorValue(2) > 900:
            self.myObject.setOutputState(0, True)
            self.after(2000, self.touchSensorLoop, time_at_program_start)
        else:
            self.after_idle(self.touchSensorLoop, time_at_program_start)

answered Jul 10, 2015 at 17:54

Noctis Skytower

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2 Comments

martineau Over a year ago

You're assuming self has after() and after_idle() methods.

Bryan Oakley Over a year ago

@martineau: It's probably a correct assumption. self appears to be a Frame or some other container, because it's used as the first argument when creating buttons... Still, it might be good to spell out that assumption in the answer.

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