A lot of beginner tutorials start with “Hello World” examples. There are plenty of websites that use a calculator application as a kind of “Hello World” for GUI beginners. Calculators are a good way to learn because they have a set of widgets that you need to lay out in an orderly fashion. They also require a certain amount of logic to make them work correctly. For this calculator, let’s focus on being able to do the following:
If you’d like to get a copy at a cheaper price than it will be when it is released in May later this year, the Kickstarter is really the way to go. You can check out the current table of contents in this post from last week.
I am pleased to announce my latest book project, Creating GUI Applications with wxPython which I am running a Kickstarter campaign for.
Creating GUI Applications with wxPython is a book that will teach you how to use wxPython to create applications by actually creating several mini-programs. I have found that while learning how the various widgets work in wxPython is valuable, it is even better to learn by creating a simple application that does something useful.
The code in this book will be targeted for Python 3 only using wxPython 4.
For more information, please check out the Kickstarter.
Let’s break this down a bit. You will notice at the top of the code that we need to import the Grid widget separately in wxPython. We also need to import a mixin called GridWithLabelRenderersMixin. We subclass the Grid class and add in the mixin and then initialize both.
Next we create a subclass of GridLabelRenderer, which is also from the mixin. This allows us to create a spacing Draw method that will give us the ability to apply different colors or fonts to the labels in our Grid. In this case, I just made it so that we could change the color of the text in the labels.
The last piece of code that we are interested in is in the MyPanel class where we actually instantiate the Grid and change the color of the background of the labels in the columns. Here is what the grid ended up looking like:
The wxPython toolkit has dozens of pre-built widgets that you can use to create cross-platform user interfaces. The wxPython demo has a much more involved example than this article does that you might also find interesting. If you haven’t given wxPython a try, you really should go get it. It is pip installable from PyPI and compatible with Python 3.
I see questions relating to the title of this article a lot. How do I open a second frame / window? How do I get all the frames to close when I close the main application? When you are first learning wxPython, these kinds of questions can be kind of hard to find answers for as you aren’t familiar enough with the framework or the terminology to know how to search for the answers.
A common UI element that you used to see a lot of was the Splash Screen. A splash screen is just a dialog with a logo or art on it that sometimes includes a message about how far along the application has loaded. Some developers use splash screens as a way to tell the user that the application is loading so they don’t try to open it multiple times.
wxPython has support for creating splash screens. In versions of wxPython prior to version 4, you could find the splash screen widget in wx.SplashScreen. However in wxPython’s latest version, it has been moved to wx.adv.SplashScreen.
Let’s look at a simple example of the Splash Screen:
Here we create a subclass of wx.Frame and we load up an image using wx.Bitmap. You will note that wx.Bitmap does not actually require you to only load bitmaps as I am using a PNG here. Anyway, the next line instantiates our splash screen instance. Here we pass it the bitmap we want to show, a flag to tell it how to position itself, a timeout in milliseconds for how long the splash screen should show itself and what its parent should be. These are all required arguments.
There are also three additional arguments that the splash screen widget can accept: pos, size and style. You will note that in this example we tell the splash screen to center itself onscreen. We could also tell it to center on its parent via SPLASH_CENTRE_ON_PARENT.
You will, of course, need to modify this example to use an image of your own.
The splash screen is actually pretty useful if you have an application that takes a long time to load. You can easily use it to distract the user and give the illusion that your application is still responsive even when it hasn’t fully loaded yet. Give it a try and see what you think.
The other day, I saw an interesting question in the wxPython IRC channel. They were asking if there was a way to set which display their application would appear on. Robin Dunn, the creator of wxPython, gave the questioner some pointers, but I decided to go ahead and write up a quick tutorial on the topic.
The wxPython toolkit actually has all the bits and pieces you need for this sort of thing. The first step is getting the combined screen size. What I mean by this is asking wxPython what it thinks is the total size of the screen. This would be the total width and height of all your displays combined. You can get this by calling wx.DisplaySize(), which returns a tuple. If you would like to get individual display resolutions, then you have to call wx.Display and pass in the index of the display. So if you have two displays, then the first display’s resolution could be acquired like this:
index = 0
display = wx.Display(index)
geo = display.GetGeometry()
Every now and then, someone will ask about how they can run the demo code from wxPython’s demo outside of the demo. In other words, they wonder how you can extract the code from the demo and run it in your own. I think I wrote about this very topic quite some time ago on the wxPython wiki, but I thought I should write on the topic here as well.
What to do about the log
The first issue that I always see is that the demo code is riddled with calls to some kind of log. It’s always writing to that log to help the developer see how different events get fired or how different methods get called. This is all well and good, but it makes just copying the code out of the demo difficult. Let’s take the code from the wx.ListBox demo as an example and see if we can make it work outside of the demo. Here is the demo code: Continue reading How to Use wxPython Demo Code Outside the Demo→