Python: Tkinter LabelFrame: How to make the surrounding line of the LabelFrame expand with the window

Question

The aim of my code is that the LabelFrame-line expands with the window. I already looked up several different solutions that work alone but not within the class I want to use.

The following is the code I wish to adapt (Code_1):

import tkinter as tk

class window(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

        # LabelFrame
        self.group = tk.LabelFrame(self, text="My first Label Frame")
        self.group.pack(expand="yes", fill="both")

        # Label inside LabelFrame
        self.label = tk.Label(self.group, text="Hello")
        self.label.pack()



root = tk.Tk()
app = window(root)
app.mainloop()

It gives me this Result: Result_Code_1

And this is the code that is working alone (Code_2):

import tkinter as tk

root = tk.Tk()

labelframe = tk.LabelFrame(root, text="This is a LabelFrame")
labelframe.pack(fill="both", expand="yes")

left = tk.Label(labelframe, text="Inside the LabelFrame")
left.pack()

root.mainloop()

Result_Code_2

Question: What is causing the difference of behaviour between Code_1 and Code_2 and how can I modify Code_1 to act the same way as Code_2 does?

Answer 1

Because the first one is inside a frame which is inside the root window itself. But the second one is directly inside the root window without being inside any container widget:

class window(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

This means your widgets will inherit from the Frame widget as long as you make their parents self .
Add a Frame widget to your second code (whose parent is root ) and make this the parent of the LabelFrame widget:

frm = tk.Frame(root)
frm.pack()

labelframe = tk.LabelFrame(frm, text="This is a LabelFrame")
labelframe.pack(fill="both", expand="yes")

Now you are getting the same view with the first code.

And in order to make Code_1 to act the same way as Code_2 does: Change this:

class window(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

to this:

class window(tk.Frame):
    def __init__(self, master):
        self.master = master

And change this:

self.group = tk.LabelFrame(self, text="My first Label Frame")

to this:

self.group = tk.LabelFrame(master, text="My first Label Frame")

Also, change: app.mainloop() to: root.mainloop() .