Python - GUI Programming - PanedWindow Widget

Python's PanedWindow widget is a container widget that can hold two or more child widgets and divides its available space into panes. Users can adjust the size of the panes by dragging a separator that divides the panes.

In this tutorial, we'll explore the PanedWindow widget in detail and create a simple GUI application using it.

Creating a PanedWindow Widget

To create a PanedWindow widget, we first need to import the tkinter module and then create an instance of the PanedWindow class:

import tkinter as tk
root = tk.Tk()
paned_window = tk.PanedWindow(root, orient=tk.HORIZONTAL)
paned_window.pack(fill=tk.BOTH, expand=True)
left_pane = tk.Label(paned_window, text="Left Pane")
paned_window.add(left_pane)
right_pane = tk.Label(paned_window, text="Right Pane")
paned_window.add(right_pane)
root.mainloop()

In this example, we first create a Tk object and then create an instance of the PanedWindow class with the parent widget as the Tk object. We set the orient parameter to tk.HORIZONTAL, which specifies that the panes should be arranged horizontally.

Next, we create two Label widgets as child widgets of the PanedWindow and add them using the add() method. We then call the pack() method on the PanedWindow to fill and expand it to fill the available space in the Tk window.

Configuring the Panes

We can configure the panes of the PanedWindow widget using several methods. For example, we can set the minimum and maximum sizes of each pane using the paneconfigure() method:

paned_window.paneconfigure(left_pane, minsize=100, maxsize=200)
paned_window.paneconfigure(right_pane, minsize=200, maxsize=400)

In this example, we set the minimum size of the left pane to 100 and the maximum size to 200. Similarly, we set the minimum size of the right pane to 200 and the maximum size to 400.

We can also set the initial size of each pane using the configure() method:

paned_window.configure(sashrelief=tk.RAISED, sashwidth=5, sashpad=5)
paned_window.sashpos(0, 200)

In this example, we set the sashrelief parameter to tk.RAISED, which specifies that the separator should be raised above the surrounding panes. We also set the sashwidth parameter to 5, which specifies the width of the separator in pixels. Finally, we set the sashpad parameter to 5, which specifies the padding around the separator in pixels.

We then set the initial position of the separator using the sashpos() method. The first parameter is the index of the pane (0 for the left pane and 1 for the right pane), and the second parameter is the position of the separator in pixels.

Handling Events

The PanedWindow widget in Tkinter is a container widget that allows you to split the window into multiple panes or frames. It contains a handle, which is a separator between two panes and can be dragged to adjust the size of each pane.

In order to handle events with the PanedWindow widget, we need to create a function that will be triggered whenever an event occurs. We can do this using the bind() method, which binds a function to a specific event.

Let's say we have a PanedWindow widget called paned_window and we want to trigger a function called handle_paned_event() whenever the user drags the handle. We can do this by calling the bind() method on the PanedWindow widget like this:

paned_window.bind("<B1-Motion>", handle_paned_event)

This code binds the handle_paned_event() function to the <B1-Motion> event, which is triggered when the user drags the handle with the left mouse button.

Now let's create the handle_paned_event() function:

def handle_paned_event(event):
    sash_position = event.widget.sashpos(0)
    print("Sash position:", sash_position)

This function takes an event object as its parameter, which contains information about the event that occurred. In this case, we're interested in the position of the handle, which we can access using the sashpos() method on the event widget.

The sashpos() method takes an index that specifies which pane's sash we're interested in. In this case, we only have two panes, so we use an index of 0 to get the position of the first pane's sash.