Python tkinter RadioButton回调函数

Question

This comes from a button that when pressed generates a radiobutton. I am not able to access to the choice made with radiobutton. Everything works fine, but the output of selected function is zero. I try using both local and global var but the result is the same.

def callback_st(): # RadioButton select technology
    var = IntVar()
    m=0
    for m in range(len(un_tech)):
        Radiobutton(radio_frame, text=un_tech[m], value=m, variable=var,
                    command=selected(var)).pack(anchor=W)

def selected(var):
    print(var)

This doesn't work. I solved using lambda:

    def selected(jst):
        global sel_technology
        sel_technology=un_tech[jst]
        print(sel_technology)

def callback_st(): #RadioButton select technology
    var_st = IntVar()
    m=0
    for m in range(len(un_tech)):
    Radiobutton(radio_frame, text=un_tech[m], value=m, variable=var_st,
                command = lambda jst=m: selected(jst)).pack(anchor=W)

This works as i want, but it isn't the solution that i want and i think is not the correct way. So, somebody can help me to find the right way?

Answer 1

In your first try, you call selected immediately, when var has a value of 0 . You avoided this with the lambda expression, but you are correct that this is an awkward workaround for the original mistake. Make var global and have selected access it as a global. Modifying your first code:

var = IntVar()
def selected():
    print(var.get())
def callback_st():
    ...
         ...command=selected...

If you were defining a class and methods, var would be an instance attribute instead of global.