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:
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→
I recently had my self-published book, “wxPython Cookbook” picked up by Apress and republished as wxPython Recipes. Since they gave me a few complimentary paperback copies, I have decided to do a little contest.
Post a comment telling me why you would want a copy
The most clever or heartfelt commenter will be chosen by me
The contest will run starting now until Monday, January 15th @ 11:59 p.m. CST.
The winner will be contacted by yours truly and I will sign the book and ship it wherever you want me to.
For those of you who want to purchase the book, Apress gave me a lame 20% off coupon that you can use for either the eBook or Paperback on their website: wx20
I was contacted earlier this year by Apress about republishing my book, wxPython Cookbook, under their branding. I thought it might be fun to see what I could learn from a publisher so I went with them as I have enjoyed several of their books in the past. The biggest change to the book is that I ended up grouping recipes into chapters instead of having each recipe be a stand-alone chapter. I also added a few new recipes to help fill in when some chapters weren’t easily sorted into groups.
Anyway, Apress just released the book in the past couple of days:
You can find the book over on Amazon or on the Apress website. You can also see a preview of the book on Google.
You can get 20% off of the book from Apress by using the following code: wx20. This code is good on the paperback and the eBook versions of the book until June 2018.
Regardless, feel free to check it out. If you already bought a copy of the wxPython Cookbook, then you don’t need to get this one too since it’s basically the same thing with a bit more polish and a handful of new recipes. I have plans for some other books that I will be self-publishing hopefully in 2018, so keep an eye on the blog for news about that!
I was recently asked about how to implement drag-and-drop of items in a wx.ListCtrl or in ObjectListView. Unfortunately neither control has this built-in although I did find an article on the wxPython wiki that demonstrated one way to do drag-and-drop of the items in a ListCtrl.
However I did think that implementing some buttons to move items around in an ObjectListView widget should be fairly easy to implement. So that’s what this article will be focusing on.
Changing Item Order
If you don’t have wxPython and ObjectListView installed, then you will want to use pip to install them: