Tkinter Checkbutton doesn't change my variable

Question

I'm trying to use a Checkbutton with a function, my_var never changes but it always call my function.

here the code:

my_var = False
def controllo_carta():
    global my_var
    print str(my_var)

[...]

c = tk.Checkbutton(toolbar, text="press me",onvalue=True,offvalue=False,variable=my_var,command=controllo_carta)
c.select()
c.pack(side=tk.LEFT,padx=2,pady=2)

print 'my var:' + str(my_var)

[...]

where is my mistake?

thanks!

Answer 1

To make your code work I would use BooleanVar() and the associated get() method to retrieve its value (http://effbot.org/tkinterbook/variable.htm)

For example: (from: http://effbot.org/tkinterbook/checkbutton.htm)

from Tkinter import *

master = Tk()

var = BooleanVar()

def cb():
    print "variable is {0}".format(var.get())

c = Checkbutton(master, text="Press me", variable=var, command=cb)
c.pack()

mainloop()