The Python Papers

wxPython - Creating a Simple Image Viewer

Mike Driscoll — Wed, 22 Apr 2026 16:50:30 GMT

The first step in creating an application is to come up with an idea. You could try to copy something simple like Microsoft Paint or Notepad. You will quickly find that they aren’t so easy to emulate as you would think, though! So instead, you will create a simple application that can load and display a photo.

When it comes to creating a GUI application, it is a good idea to think about what it will look like. If you enjoy working with pencil and paper, you could draw a sketch of what your application will look like. There are many software applications you can use to draw with or create simple mock-ups. To simulate a Sizer, you can draw a box.

Here is a mockup of what the finished application should look like:

Now you have a goal in mind. This allows you to think about how you might lay out the widgets. Go ahead and create a new file named image_viewer.py and add the following code to it:

Here you create a new class named ImagePanel() that will hold all your widgets. Inside it, you have a wx.Image, which you will use to hold the photo in memory in an object that wxPython can work with. To display that photo to the user, you use wx.StaticBitmap. The other widget you need is the familiar wx.Button, which you will use to browse to the photo to load.

The rest of the code lays out the widgets using a vertically oriented wx.BoxSizer. You use the sizer’s Fit() method to try to make the frame “fit” the widgets. What that means is that you want the application to not have a lot of white space around the widgets.

When you run this code, you will end up with the following user interface:

That looks almost right. It looks like you forgot to add the text entry widget to the right of the browse button, but that’s okay. The objective was to try and get a close approximation to what the application would look like in the end, and this looks pretty good. Of course, none of the widgets actually do anything yet.

Your next step is to update the code so it works. Copy the code from the previous example and make a new file named image_viewer_working.py. There will be significant updates to the code, which you will learn about soon. But first, here is the full change in its entirety:

This change is pretty long. To make things easier, you will go over each change in its own little chunk. The changes all occurred in the ImagePanel class, so you will go over the changes in each of the methods in turn, starting with the constructor below:

There are a few minor changes here. The first one is that you added a max_size for the image. Then you hooked up an event to the the browse button. This button will now call on_browse() when it is clicked.

The next change is that you added a new widget, a wx.TextCtrl to be precise. You stored a reference to that widget in self.photo_txt, which will allow you to extract the path to the photo later.

The final change is that you now have two sizers. One is horizontal and the other remains vertical. The horizontal sizer is for holding the browse button and your new text control widgets. This allows your to place them next to each other, left-to-right. Then you add the horizontal sizer itself to the vertical main_sizer.

Now let’s see how on_browse() works:

Here you create a wildcard which is used by the wx.FileDialog to filter out all the other files types except the JPEG format. Next, you create the wx.FileDialog. When you do that, you set its parent to None and give it a simple title. You also set the wildcard and the style. style is an open file dialog instead of a save file dialog.

Then you show your dialog modally. This means the dialog will appear over your main application and prevent you from interacting with it until you have accepted or dismissed the file dialog. If the user presses the OK button, then you will use GetPath() to get the path of the selected file and set the text control to that path. This effectively saves off the photo’s path so you can use it later.

Lastly, you call load_image() which will load the image into wxPython and attempt to show it. You can find out how by reading the following code:

The first step in this method is to extract the filepath from the text control widget. Then you pass that path along to a new instance of wx.Image. This will load the image into wxPython for you. Next, you get the width and height from the wx.Image object and use the max_size value to resize the image while maintaining its aspect ratio. You do this for two reasons. The first is because if you don’t, the image will get stretched out or warped. The second is that most images at full resolution won’t fit on-screen, so they need to be resized.

Once you have the new width and height, you Scale() the image down appropriately. Then you call your wx.StaticBitmap control’s SetBitmap() method to update it to the new image that you loaded. Finally, you call Refresh(), which will force the bitmap widget to redraw with the new image in it.

Here it is with a butterfly photo loaded in it:

Now you have a fully-functional application that can load JPEG photos. You can update the application to load other image types if you’d like. The wxPython toolkit uses Pillow, so it will load the same types of image file types that Pillow itself can load.

Wrapping Up

The wxPython toolkit is extremely versatile. It comes with many, many widgets built-in and also includes a wonderful demo package. The demo package will help you learn how to use the widgets in your own code. You are only limited by your imagination.

Play around with the code in this tutorial and then take a look at the demo package when you get a chance. Then start creating your own neat applications!

Python 101 - How to Create an "exe" for Mac

Mike Driscoll — Tue, 14 Apr 2026 13:31:13 GMT

Each operating system has its own method of installing or running an application. On Windows, you run an executable most of the time. Executables have an extension of .exe. Apple’s Mac software has the concept of applications that use the extension .app. These are technically a bundle of files including a runnable binary. They are kind of like a runnable zip-file. All you need to do is double-click the .app file to run it.

If you want to distribute a Python application on Mac OSX, you have three options:

PyInstaller - https://www.pyinstaller.org/
Briefcase - https://beeware.org/project/projects/tools/briefcase/
py2app - https://py2app.readthedocs.io/en/latest/

You learned about the PyInstaller package in chapter 44. In this chapter you will learn how to use PyInstaller to create an .app bundle.

In this tutorial, you will cover the following two topics:

Installing PyInstaller
Creating an Executable with PyInstaller

Being able to create .app bundles gives to a way to distribute your application to Mac users. Let’s find out how to install the Python packages that you need so you can get started!

Installing PyInstaller

Both PyInstaller and Briefcase can be installed using pip. Here is how you would install PyInstaller:

python -m pip install pyinstaller

This is a pretty quick installation because PyInstaller has a few dependencies. Once PyInstaller is installed, you can move on to the next section and create an executable for Mac OSX.

Creating an Executable with PyInstaller

Creating an executable requires code. You can use a simple wxPython application for this tutorial. Here is the image_viewer program code that you can use to open and display images:

You can use the same commands for PyInstaller that you use on Windows to create a Mac application bundle. Open up a console window on your Mac and navigate to the folder that contains image_viewer.py. Then run the following command:

pyinstaller image_viewer.py --windowed

Running this command will give you this output, which is quite similar to the output you would see on Windows:

Of course, when you run PyInstaller on a Mac, you will see that the platform information reflects that. When this finishes, you will have a dist folder that contains your app bundle. There does seem to be a bug in Python 3.7 and 3.8 that occurs when you try to launch the app bundle:

FileNotFoundError: Tcl data directory

To fix this issue, you will need to run the following commands in your console:

Now, when you go to run the application bundle, it will launch your wxPython GUI correctly. Because of this issue, if you use the --onefile option, you won’t be able to add those two folders. So the --onefile option won’t actually launch. Instead, you will see it attempt to launch and immediately crash. Hopefully, PyInstaller or a newer version of Python will resolve this issue.

Wrapping Up

Creating executables on macOS is a bit more complicated than on Windows. You also have fewer options for creating application bundles. Windows offers many Python packages to choose from for creating binaries. Mac has PyInstaller and Beeware’s Briefcase. The latter is designed to work with other Beeware products, but can be used with regular Python too.

Go ahead and give them both a try to see what works best for you. PyInstaller is a much more mature option, but sometimes it’s nice to try newer packaging applications.

Get the Book

Did you enjoy this article? Well, it’s from my book, Python 101 - 2nd Edition. Check it out at any of the following websites:

Textual - An Intro to DOM Queries (Part II)

Mike Driscoll — Wed, 08 Apr 2026 17:06:39 GMT

Last week, you learned the basics of Textual’s DOM queries. If you missed it, you can read the article now!

In this tutorial you will be learning about the following topics:

The DOMQuery object
Getting the first or last widget
Query filters
Query exclusions
Other query methods

Let’s get started!

The DOMQuery Object

The DOMQuery object gets returned whenever you …

Textual - An Intro to DOM Queries (Part I)

Mike Driscoll — Tue, 31 Mar 2026 17:54:55 GMT

In this article, you will learn how to query the DOM in Textual. You will discover that the DOM keeps track of all the widgets in your application. By running queries against the DOM, you can find widgets quickly and update them, too.

You will be learning the following topics related to the DOM:

The query one method
Textual queries

You will learn more in th…

Python Pop Quiz - List Popping

Mike Driscoll — Thu, 26 Mar 2026 15:05:09 GMT

The Python list data type is much like an array in other programming languages. The list includes many different methods. You can get a full listing of those methods like this:

my_list = []
print(dir(my_list))

One of those methods is called pop(). You can pass an index of the item you want to pop from the list (if you don’t, the last item is chosen). That…

Python Pop Quiz - Truthy or Falsey

Mike Driscoll — Wed, 18 Mar 2026 13:40:58 GMT

Python supports Booleans in much the same way as other programming languages do. In Python’s case, it uses the True and False keywords. But there is also the concept of truthy and falsey. An example of a truthy value in Python is a number greater than zero (also a number less than zero), and an example of a falsey value would be an empty string. When us…

Textual - Creating a Custom Checkbox

Mike Driscoll — Wed, 11 Mar 2026 18:04:42 GMT

Textual is a great Python user interface package. Textual lets you create a GUI-like interface in your terminal.

You can use many different widgets in Textual. However, the widget you will be focusing on in this tutorial is the humble checkbox.

Checkboxes are used for Boolean choices. They return a True if checked and a False if unchecked. You can use a c…

Python Pop Quiz - Positional Arguments

Mike Driscoll — Thu, 05 Mar 2026 13:37:38 GMT

Python functions can take in several different types of arguments. What are the different argument types called?

If you don’t know, you should review the following:

Positional arguments
Keyword arguments

This information may help you solve the quiz, or it may confuse you more. Read the next section when you’re ready to take a crack at it!

The Quiz

How do you …

Python Pop Quiz - Type Addition

Mike Driscoll — Wed, 25 Feb 2026 13:43:24 GMT

Python has multiple built-in functions you can use to introspect your code. You’ll learn more about those functions in a later quiz.

For this quiz, you’ll focus on isinstance(), a function you can use to check if a variable is a particular type. For example, you might want to check if a variable is a string or an integer.

Good luck!

The Quiz

What will be th…

Python Pop Quiz - Letter Explosion

Mike Driscoll — Tue, 17 Feb 2026 15:17:53 GMT

You learned about exploding a range object in the last quiz. For this quiz, you will extend that knowledge and discover what happens when you explode a string.

But wait! There’s more here than meets the eye. What is up with the numbers in the squiggly brackets?

If you’re familiar with string methods, you can figure this quiz out pretty quickly!

The Quiz

Wha…

Python Basic Type Hinting

Mike Driscoll — Tue, 10 Feb 2026 17:13:09 GMT

When Python first added type hinting to the language in version 3.5, you could only add type hints to functions. However, in Python 3.6, the language added the ability to annotate variables as well. Over the following years, Python has steadily added more features to its type hinting capabilities and slowly refined the typing interface.

You will be study…

Python Pop Quiz - Number Explosion

Mike Driscoll — Fri, 06 Feb 2026 00:43:48 GMT

You will sometimes come across examples of code that use one or two asterisks. Depending on how the asterisks are used, they can mean different things to Python.

Check your understanding of what a single asterisk means in the following quiz!

The Quiz

What will be the output if you run this code?

A) {range}

B) (range)

C) [0, 1, 2]

D) (0, 1, 2)

E) {0, 1, 2}

St…

Python Typing Book Kickstarter

Mike Driscoll — Tue, 03 Feb 2026 15:25:28 GMT

Python has had type hinting support since Python 3.5, over TEN years ago! However, Python’s type annotations have changed repeatedly over the years. In Python Typing: Type Checking for Python Programmers, you will learn all you need to know to add type hints to your Python applications effectively.

You will also learn how to use Python type checkers, con…

Vibe Coding Pong with Python and pygame

Mike Driscoll — Wed, 28 Jan 2026 13:48:22 GMT

Pong is one of the first computer games ever created, way back in 1972. If you have never heard of Pong, you can think of it as a kind of “tennis” game. There are two paddles, on each side of the screen. They move up and down. The goal is to bounce a ball between the two paddles. If you miss the ball, your opponent scores a point.

Atari created Pong and …

Python 101 - Introspection

Mike Driscoll — Thu, 22 Jan 2026 13:36:03 GMT

One of the reasons Python is special is that it provides lots of tools that allow you to learn about Python itself. When you learn about yourself, it is called introspection. There is a similar type of introspection that can happen with programming languages.

Python provides several built-in functions that you can use to learn about the code that you are…

New Book: Vibe Coding Video Games with Python

Mike Driscoll — Thu, 15 Jan 2026 12:46:21 GMT

My latest book, Vibe Coding Video Games with Python, is now available as an eBook. The paperback will be coming soon, hopefully by mid-February at the latest. The book is around 183 pages in length and is 6x9” in size.

Vibe Coding Video Games with Python

In this book, you will learn how to use artificial intelligence to create mini-games. You will attempt…

Textual - How to Log to Both the Console and a File

Mike Driscoll — Tue, 13 Jan 2026 14:41:39 GMT

Textual is a wonderful Python package that allows you to create a text-based user interface (TUI) in your terminal. You may have read about Textual several times in this newsletter.

When you are debugging Textual applications, you can log or print to something called the Textual console. You run this console in a separate terminal and then run your Textu…

How to Type Hint a Decorator in Python

Mike Driscoll — Tue, 06 Jan 2026 19:25:45 GMT

Decorators are a concept that can trip up new Python users. You may find this definition helpful: A decorator is a function that takes in another function and adds new functionality to it without modifying the original function.

Functions can be used just like any other data type in Python. A function can be passed to a function or returned from a functi…

How to Switch to ty from Mypy

Mike Driscoll — Tue, 30 Dec 2025 14:48:34 GMT

Python has supported type hinting for quite a few versions now, starting way back in 3.5. However, Python itself does not enforce type checking. Instead, you need to use an external tool or IDE. The first and arguably most popular is mypy.

Microsoft also has a Python type checker that you can use in VS Code called Pyright, and then there’s the lesser-kn…

Product Review: Python Flash Cards

Mike Driscoll — Tue, 23 Dec 2025 14:10:23 GMT

No Starch Press is best known for creating books on computer programming. However, they recently released a new product called Python Flash Cards by Eric Matthes, the author of Python Crash Course. I thought this was a unique product and decided to ask for a review copy.

The cards and their box are high-quality. I like the cardstock they used quite a bit…