Python Tkinter Example

By | June 23, 2020
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This post works through a simple example of creating a GUI in python using Tkinter. The python tkinter example goes through some simple things that a GUI would need to do such as creating new windows, text input, and labels.

This isn’t a tutorial as such, but instead I’ve tried to pick out a few of the basics of tkinter so that they are in one place. You can use this basic example as a starting point for more sophisiticated GUI applications.

This example is available on github.

tkinter example

Why Tkinter?

There are a number of GUI libraries available for python, so why tkinter?

  • Portability – Tkinter is also designed to make use of the existing styling of the operating system it is running in, rather than bringing its own widgets.
  • Simplicity – Tkinter is also fairly simple to get started with (as you will see in this example), so is good for
  • Availability – Tkinter is typically packaged with python, so if package availability is a challenge for you, then Tkinter may make sense

An Example

In this example I’m going to step through the creation of a simple GUI featuring:

  • A main window
  • Two sub-windows
  • Creating an alert box
  • Creating an ‘About’ menu item

I have deliberately left out the less essential parts of the GUI design such as sizing and exact layout. This is important to consider, but for the purposes of learning I find it can distract from the truly essential parts of the code.

Create The Main Window

We’re going to be making main window that looks like this – two buttons that open sub-windows, and a Help menu.

import tkinter
from tkinter import messagebox
import os

window = tkinter.Tk()

window.title("Main Window")

# create a toplevel menu
menubar = tkinter.Menu(window)
helpmenu = tkinter.Menu(menubar)

menubar.add_cascade(label="Help", menu=helpmenu)
helpmenu.add_command(label="About")

# display the menu
window.config(menu=menubar)

btn = tkinter.Button(window, text="Sub-window 1")
btn.pack(anchor='center')

btn2 = tkinter.Button(window, text="Sub-window 2")
btn2.pack(anchor='center')

window.mainloop()

At this stage the buttons won’t do anything. We’ll add that later.

Add an ‘About’ box

Next, we add an ‘About’ option to the ‘Help’ menu:

Clicking that ‘About’ option will create an ‘About box’

We do this by first creating a function to hold the details of this new ‘About’ window, along with a corresponding reference to that function in the button click.

First, we’ll create a function to hole the ‘About’ window:

def create_about():
    about_window = tkinter.Toplevel(window)
    about_window.title('About')
    lbl = tkinter.Label(about_window, text="About")
    lbl.config(anchor=tkinter.CENTER)
    lbl.pack(anchor='center')
    btn = tkinter.Button(about_window, text="OK", command=about_window.destroy)
    btn.pack(anchor='center')

And then update the ‘helpmenu’ menu bar to include a command which points to that new function.

helpmenu.add_command(label="About", command=create_about)

 

Add the First Sub-window

In this first sub-window, we’ll add quite a bit of functionality:

  • Close a window with a click
  • Add text box / label to a window
  • Centering text box / label
  • Get a value from a button click
  • Use a button to run non-UI functionality
  • Use a button to create an information box

As with the ‘about’ box, we can keep the details of this new sub-window inside its own function, and then reference this function in the button click.

First we can update the button click to reference a function:

btn = tkinter.Button(window, text="Sub-window 1", command=create_subwindow1)

And then add the function itself

def create_subwindow1():
    def retrieve_input():
        entryText = entry.get()

        if os.path.exists(entryText):
            lbl2.config(text='A file')
        else:
            lbl2.config(text='Not a file')

    sub_window = tkinter.Toplevel(window)
    sub_window.title('Sub-window 1')
    lbl = tkinter.Label(sub_window, text="Sub-window 1")
    lbl.config(anchor=tkinter.CENTER)
    lbl.pack(anchor='center')
    btn = tkinter.Button(sub_window, text="Close", command=sub_window.destroy)
    btn.pack(anchor='center')

    lbl2 = tkinter.Label(sub_window, text="")
    lbl2.pack(anchor='center')

    entry = tkinter.Entry(sub_window)
    entry.pack(anchor='center')

    buttonCommit=tkinter.Button(sub_window, text="Check path exists",
                                command=retrieve_input)

    buttonCommit.pack(anchor='center')

    btn2 = tkinter.Button(sub_window, text="Functionality 2", command=lambda: messagebox.showinfo("Info","Not Yet Implemented"))
    btn2.pack(anchor='center')

The resulting sub-window should look like this:

And the ‘Not Yet Implemented’ info message when we click on Functionality 2 comes up as this:

Add the Second Sub-window

Finally we’ll add the code for the second sub-window, although this time we are actually going to make a warning window.

Again, we follow the same pattern of updating the button ‘command’ attribute. A difference here is that rather than creating a separate function, we instead create a inline, lambda function to hold the message box creation:

btn2 = tkinter.Button(window, text="Sub-window 2", command=lambda: tkinter.messagebox.showwarning("Warning","Warning message"))