窗口标签未打印：Python

Question

I want to create two windows.

Behaviour of windows:

Window1 has a label and a button . When I click on that button , 2nd window has to open. 2nd window have a label .

Problem:

Label in 2nd window is not appearing.

Code:

def window1():
    root = tkinter.Tk()
    root.geometry("200x200")
    root.title("Window1")
    var = tkinter.StringVar()

    tkinter.Label(root,  textvariable = var, bg = "red").grid(row = 0, column = 0)
    var.set("This is window1")

    tkinter.Button(root, text = "Button1", command = OnBut).grid(row =  0, column = 1)

    root.mainloop()

def OnBut():
    window2()

def window2():
    root = tkinter.Tk()
    root.title("Window2")
    root.geometry("250x250")

    var = tkinter.StringVar()

    tkinter.Label(root,  textvariable = var, bg = "blue").grid(row = 1, column = 0, padx = 3, pady = 3)
    tkinter.Button(root, text = "Button", command = OnBut).grid(row =  0, column = 1, padx  =3, pady = 3)
    var.set("This is window2")       #not appearing <-- problem

    root.mainloop()

window1()

when I call window2 seperately, its working fine. Why label not printing in 2nd window, by clicking on button ?

Answer 1

You don't really need a real function for your command in this case. This is what lambda s are made for -- callbacks!

Remove your onBut function (which is the problem anyway, since root isn't defined there) and replace your command in each button with:

command = lambda: window2(root)

Currently, when you call onBut , it tries to do:

window2(root)
# HELP I DON'T KNOW WHAT root IS!!

This throws a NameError on my copy. Your code may vary.

Since you're editing willy nilly, let me just write you some working code.

import tkinter

def run():
    root = tkinter.Tk()
    root.title("Window1")
    s_var = tkinter.StringVar()
    tkinter.Label(root, textvariable = s_var).pack()
    tkinter.Button(root, text = "Button", command = lambda: makewindow(root)).pack()
    s_var.set("Window #1")

def makewindow(root):
    top = tkinter.Toplevel(root)
    top.title("Window2")
    s_var = tkinter.StringVar()
    tkinter.Label(top, textvariable = s_var).pack()
    tkinter.Button(top, text = "Button", command = lambda: makewindow(root)).pack()
    s_var.set("Window #2")

if __name__ == "__main__":
    run()