How do I set the default value of a TkInter widget?

Question

I have a Checkbutton that I need ticked as a default when I open the window. Setting the variable to the on value doesn't seem to work, so what should I do? Here is a short, self contained example of what yields an unticked checkbox.

#!/usr/bin/python3

from tkinter import ttk
from tkinter import *
class Sizzle(Frame):

    def __init__(self, parent):
        Frame.__init__(self, parent)   

        self.parent = parent

        self.initUI()
    def initUI(self):
        self.parent.title("Sizzle")
        self.style = ttk.Style()
        self.style.theme_use("default")
        self.pack(fill=BOTH, expand=1)
        ifalphagrams=BooleanVar()
        b=Checkbutton(self, variable=ifalphagrams, onvalue=True, offvalue=False)
        b.grid(row=1,column=3 ,sticky=W)
        b.select()
def main():

    root = Tk()
    root.geometry("700x700+700+700")
    app = Sizzle(root)
    root.mainloop()  
if __name__ == '__main__':
    main()  

Answer 1

Most likely you're using a local variable to hold the reference to the StringVar , and it's getting garbage collected. When you prevent the variable from being garbage-collected your code works fine:

from Tkinter import *

class Example(Frame):
    def __init__(self, parent):
        Frame.__init__(self, parent)

        ifalphagrams = StringVar()
        alp = Checkbutton(self, variable=ifalphagrams, onvalue='yes', offvalue='no')
        alp.grid(row=1,column=3, sticky=W)
        alp.select()
        self.ifalphagrams = ifalphagrams

if __name__ == "__main__":
    root = Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()