Question

Exercise: Advanced counting

Complete the program below in the answer box by entering functions so the program can modify the value variable either by adding 1, adding 5, subtracting 1, or subtracting 5. There should only be one function updating the value. The functions subtract_one, add_one, etc. are helper functions as described above; they should simply call the value update function.

from tkinter import *
from tkinter.ttk import *

# Write your functions here

def main():
"""Set up the GUI and run it"""

global value, value_label
window = Tk()
value = 0
value_label = Label(window, text=str(value))
value_label.grid(row=0, column=0, columnspan=4)
subtract_five_button = Button(window, text="-5", command=subtract_five)
subtract_five_button.grid(row=1, column=0)
subtract_one_button = Button(window, text="-1", command=subtract_one)
subtract_one_button.grid(row=1, column=1)
add_one_button = Button(window, text="+1", command=add_one)
add_one_button.grid(row=1, column=2)
add_five_button = Button(window, text="+5", command=add_five)
add_five_button.grid(row=1, column=3)
window.mainloop()

main()

Answer 1

1. Using one function

Code:

from tkinter import *
from tkinter.ttk import *

global value, value_label
window = Tk()

counter = 0  #declare counter and intialize with 0

value = StringVar()   #declare a variable for update 
value.set(str(0))   #set first value with 0
value_label = Label(window, textvariable=value)   #declare label for counter
value_label.grid(row=0, column=0, columnspan=4)

def update_counter(button):  #this function is used to add value to the counter according to the clicked button
    global counter    
    temp = counter    
    counter = counter + int(button.cget('text'))   #here update counter value with text of clicked button 
    value.set(str(counter))   #update new value to label

def main():
    
    #here whenever you click any button then update_counter function called with button as an argument 
    subtract_five_button = Button(window, text="-5", command=lambda:update_counter(subtract_five_button))   
    subtract_five_button.grid(row=1, column=0)
    
    subtract_one_button = Button(window, text="-1", command=lambda:update_counter(subtract_one_button))   
    subtract_one_button.grid(row=1, column=1)
    
    add_one_button = Button(window, text="+1", command=lambda:update_counter(add_one_button))   
    add_one_button.grid(row=1, column=2)
    
    add_five_button = Button(window, text="+5", command=lambda:update_counter(add_five_button))   
    add_five_button.grid(row=1, column=3)
    
    window.mainloop()
       
main()   #call main function to set gui to the window

Output:

After clicking +5 Button:

2. Using 4 different functions

Code:

from tkinter import *
from tkinter.ttk import *

global value, value_label
window = Tk()

counter = 0  #declare counter and intialize with 0

value = StringVar()   #declare a variable for update 
value.set(str(0))     #set first value with 0
value_label = Label(window, textvariable=value)   #declare label for displaying result
value_label.grid(row=0, column=0, columnspan=4)

def update_label(counter):#whenever any button is clicked then this function is called  
    value.set(str(counter)) #to set new value to the result 

def subtract_five():
    global counter    
    counter = counter-5     #update counter value by subtracting 5
    update_label(counter)   #then this function is clled to display the new result 
    
def subtract_one():
    global counter    
    counter = counter-1     #update counter value by subtracting 1
    update_label(counter)   #then this function is clled to display the new result 
    
def add_one():
    global counter    
    counter = counter+1     #update counter value by adding 1
    update_label(counter)   #then this function is clled to display the new result 
    
def add_five():
    global counter    
    counter = counter+5      #update counter value by subtracting 1
    update_label(counter)    #then this function is clled to display the new result 

def main():
    subtract_five_button = Button(window, text="-5", command=subtract_five)   #subtract_five() called when button clicked
    subtract_five_button.grid(row=1, column=0)
    
    subtract_one_button = Button(window, text="-1", command=subtract_one)   #subtract_one() called when button clicked
    subtract_one_button.grid(row=1, column=1)
    
    add_one_button = Button(window, text="+1", command=add_one)   #add_one() called when button clicked
    add_one_button.grid(row=1, column=2)
    
    add_five_button = Button(window, text="+5", command=add_five)   #add_five() called when button clicked
    add_five_button.grid(row=1, column=3)
    
    window.mainloop()
       

main()   #call main function to set gui to the window

Output:

After clicking +1 Button: