28. Clock

The Clock class will be used to build four counters, each working at a different rate.

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We import division from the __future__ module so Python 2.7 can also run this program. The layout is a GridLayout. There are four counters, each with its own NumericProperty. The Clock class is imported so we can have periodic functions.

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The root class has four counter variables. These are updated in the four functions, which are called at different rates.

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In the app class, we set the four rates as 1 Hz, 2 Hz, 3 Hz and 4 Hz.

# ex28.py

from __future__ import division
from kivy.uix.gridlayout import GridLayout
from kivy.app import App
from kivy.properties import NumericProperty
from kivy.clock import Clock

class Ex28(GridLayout):
    counter1 = NumericProperty(0)
    counter2 = NumericProperty(0)
    counter3 = NumericProperty(0)
    counter4 = NumericProperty(0)
    def update1(self, dt): self.counter1 += 1
    def update2(self, dt): self.counter2 += 1
    def update3(self, dt): self.counter3 += 1
    def update4(self, dt): self.counter4 += 1
    
class Ex28App(App):
    def build(self):
        ex28=Ex28()
        Clock.schedule_interval(ex28.update1, 1)
        Clock.schedule_interval(ex28.update2, 1/2)
        Clock.schedule_interval(ex28.update3, 1/3)
        Clock.schedule_interval(ex28.update4, 1/4)
        return ex28

if __name__=='__main__':
    Ex28App().run()

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In the kv file, we set the background as blue. The columns are defined to be two. We will have 8 widgets in total. This would require 4 rows.

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Next horizontal and vertical lines are drawn, dividing the screen into four equal parts.

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This creates 4 Borders around each counter. The borders are all 200 by 150 pixels in size. We use the Line command as we do not want a filled rectangle.

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There are two labels in 1st row and there are 2 buttons in 2nd row. The first row shows the values of counter 1 and counter 2. The text of the button indicates the rate of the counter, and when the button is clicked, we reset the respective counter.

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We do the same in Rows 3 and 4 but this time with counter 3 and counter 4.

# ex28.kv

<Ex28>:
    cols: 2
    canvas:
        Color:
            rgb: 0,0,1
        Rectangle:
            size: root.width,root.height
            pos: 0,0
        Color:
            rgb: 1, 0, 1
        Line:
            points: 0,root.height/2, root.width,root.height/2
            width: 5
        Line:
            points: root.width/2,0, root.width/2,root.height
            width: 5
        Color:
            rgb: .25, .25, .25
        Line:
            rectangle: 100,100, 200,150
            width: 5
        Line:
            rectangle: root.width/2+100,100, 200,150
            width: 5
        Line:
            rectangle: 100,root.height/2+100, 200,150
            width: 5
        Line:
            rectangle: root.width/2+100,root.height/2+100, 200,150
            width: 5
    Label:
        size_hint_y: .8
        text: '[size=32]'+str(root.counter1)+'[/size]'
        markup: True
    Label:
        size_hint_y: .8
        text: '[size=32]'+str(root.counter2)+'[/size]'
        markup: True
    Button:
        size_hint_y: .2
        text: '[size=32]1 Hertz[/size]'
        markup: True
        on_press: root.counter1=0
    Button:
        size_hint_y: .2
        text: '[size=32]2 Hertz[/size]'
        markup: True
        on_press: root.counter2=0
    Label:
        size_hint_y: .8
        text: '[size=32]'+str(root.counter3)+'[/size]'
        markup: True
    Label:
        size_hint_y: .8
        text: '[size=32]'+str(root.counter4)+'[/size]'
        markup: True
    Button:
        size_hint_y: .2
        text: '[size=32]3 Hertz[/size]'
        markup: True
        on_press: root.counter3=0
    Button:
        size_hint_y: .2
        text: '[size=32]4 Hertz[/size]'
        markup: True
        on_press: root.counter4=0
    

        

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This is the result after clicking to reset the 2nd, 3rd and 4th counter. For example if counter 4 had not been reset it would be around 120, 4 times the value of first counter.

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