Why is my tkinter panedwindow not stretching all the way to the bottom of the window?

Question

From looking at this for a few days, I don't understand is why the pandedwindow widget is not all the way down to the top of the bottom frame. If I block out the frame portion, the PanedWindow goes all the way to the bottom of the window.

Please feel free to criticize or give comments on how I can improve my program in terms of using class.

import tkinter as t

def main():
    root = t.Tk()
    root.geometry("350x470")
    root.config(background="LightBlue4")
    root.title("basic window")
    app = Application (root)
    root.mainloop()

class Application():

    def __init__(self, parent):
        self.window = parent

        self.panes=t.PanedWindow(self.window, sashwidth=3)
        self.panes.pack(fill=t.BOTH, expand="yes")


        self.frame1=t.Frame(self.window, bg="yellow", bd=2,     relief=t.RIDGE)   
        self.frame1.pack(anchor=t.S, fill=t.X, expand=1)

        self.createWidgets()


    def createWidgets(self):

        self.entry=t.Entry(self.frame1, width=25)
        self.entry.pack(side=t.LEFT, expand=1)
        self.label2=t.Label(self.frame1, text="Update ", fg = "light  green", bg = "dark green", font = "Helvetica 16 bold italic" , bd=2,  relief=t.RAISED)
        self.label2.pack(side=t.LEFT, fill=t.X, padx=5)
        self.label3=t.Label(self.frame1, text="Quit", fg = "blue", bg = "yellow", font = "Verdana 12 bold" , bd=2, relief=t.RAISED)
        self.label3.pack(side=t.LEFT, fill=t.X, padx=5)

        self.left = t.Label(self.window, text="Left Pane", bd=4, bg="tan",  relief=t.FLAT)
        self.left.pack()

        self.right = t.Label(self.window, text="Right Pane", bd=4, bg="light cyan", relief=t.FLAT)
        self.right.pack()

        self.panes.add(self.left, stretch="always")
        self.panes.add(self.right )
        self.panes.sash_place(0,120,0)




if __name__ == '__main__':
    main()

Answer 1

The paned window does not extend the full vertical height because it is sharing space with self.frame1 . Both have been packed with the option to expand into the available space, so they end up each taking half.

It you turn expansion off on self.frame1 , the paned window will take all of the available space:

self.frame1.pack(anchor=t.S, fill=t.X, expand=False)

Answer 2

I don't understand is why the pandedwindow widget is not all the way down to the top of the bottom frame.

Why?

That is because the way you packed self.frame1 and self.panes places these 2 widgets on top of each other. That is what you can see when comment this line: #self.createWidgets() :

How to resolve this problem?

If you want the PaneWindow widget to stretch down, you will need to pack self.frame1 and self.panes side by side using the side option:

self.panes.pack(fill=t.BOTH, expand="yes", side = t.LEFT)
self.frame1.pack(anchor=t.S, fill=t.X, expand=1, side = t.LEFT)

Result:

Better options:

1. As you have many widgets to manage, it is better to use the grid() layout manager instead of pack() .
2. For self.label2 and self.label3 use the Button() widget instead.