Tkinter: is there a way to check checkboxes by default?

Just adding onto GunnerStone's answer - Because I was looking for something where I can reset my values/checkboxes.

If you'd like to de-select the checkbox value for whatever reason, use deselect():

from Tkinter import *

CheckVar = IntVar()
self.checkbutton = Checkbutton(self.root, text = "Test", variable = CheckVar)
self.checkbutton.deselect()

or use toggle to switch between the two:

self.checkbutton.toggle()

I think the function you are looking for is .select()

This function selects the checkbutton (as can be assumed from the function name)

Try calling this function after your widget is defined:

from Tkinter import *

CheckVar = IntVar()
self.checkbutton = Checkbutton(self.root, text = "Test", variable = CheckVar)
self.checkbutton.select()

By calling the function right after the widget is created, it looks as though it's selected by default.

Your CheckVar is a local variable. It's getting garbage collected. Save it as an object attribute. Also, you can create the variable and initialize it all in one step:

self.CheckVar = IntVar(value=1)
self.checkbutton = Checkbutton(..., variable = self.CheckVar)

You can also use the select function of the checkbutton:

self.checkbutton.select()