Chechboxes in Tkinter

Question

I'm new to GUIs, and I'm writing some code segments for school. This is an issue I've been having in multiple assignments and I can't seem to wrap my head around it. When I implement checkboxes, the value returned is always positive regardless of whether or not I check to box. For example, this is a code I've been writing that is supposed to create a menu for the user to select from, and them display the correct total:

from tkinter import * 
def main(): 
    class Application(Frame):
        #GUI application that creates a menu to be chosen from and selections    to be made.
        def __init__(self, master):
            #Initialize Frame. 
            Frame.__init__(self, master)
            self.grid()
            self.createWidgets()

        def addPrices(self):
            #store price float
            price = 0.00

        #add all contents of the list selected
        #use if statement to determine which prices need to be added
            if self.isPizza:
                price += 3.00
            if self.isFries:
                price += 0.50
            if self.isCoke:
                price += 0.25
            if self.isChurro:
                price += 1.50 

        #display totals
        #Use label to print total
            Label(self,text = "Your total is: ").grid(row = 9, column = 0, columnspan = 2, sticky = W)
            Label(self,text = price).grid(row = 10, column = 0, columnspan = 2, sticky = W)   


        def createWidgets(self):
            #create instruction label 
            Label(self,text = "Please Select your Items:").grid(row = 0, column = 4, columnspan = 2, sticky = W)

            #create labels for checkboxes / menu
            Label(self,text = "Pizza.... $3.00").grid(row = 1, column = 5, sticky = W)
            Label(self,text = "Fries... $0.50").grid(row = 2, column = 5,  sticky = W)
            Label(self,text = "Coke... $0.25").grid(row = 3, column = 5,  sticky = W)
            Label(self,text = "Churro... $1.50").grid(row = 4, column = 5, sticky = W)

            #create input via checkboxes 
            #Create a plain of checkboxes to select items 
            self.isPizza = BooleanVar()
            Checkbutton(self,text = "Pizza",variable = self.isPizza).grid(row = 6, column = 0, sticky = W)
            self.isFries = BooleanVar()
            Checkbutton(self, text = "Fries",variable = self.isFries).grid(row = 6, column = 1, sticky = W)
            self.isCoke = BooleanVar()
            Checkbutton(self, text = "Coke",variable = self.isCoke).grid(row = 7, column = 0, sticky = W)
            self.isChurro = BooleanVar()
            Checkbutton(self, text = "Churro",variable = self.isChurro).grid(row = 7, column = 1, sticky = W)

            #Create submit button 
            Button(self,text = "Click to submit order",command = self.addPrices).grid(row = 8, column = 0, sticky = W)



    root = Tk()
    root.geometry("800x400") 
    root.title(" Order Up!")
    app = Application(root)
    root.mainloop()

main()

The program always returns 5.25 as the total, which is just the amount of all items added together. Am I missing a segments that will change my Boolean variables depending on user input?

Answer 1

You need to test the boolean value of the each Var's value, not of the Var itself. Change if self.isPizza: to if self.isPizza.get():, etc, and your program works.

PS Wrapping your entire program in def main: and calling main(), as you did, is useless and wastes an indentation level and makes the program harder to read. If you want to make a file useful for import, as well as direct running, define your top-level classes and functions as module level and only put code that does things that should not happen on import inside main, and then guard the execution of main. In this case:

from tkinter import *

class Application:
...
def main():
    root = Tk()
    ...
    root.mainloop()

if __name__ == '__main__':
    main()

You can now import this file into a test file and test the Application class without root.mainloop() taking control.