Jonathan Gardner's PyQt Tutorial

This is a short tutorial to get you up to speed with PyQt. It assumes some knowledge of bash, Python, and Qt.

If you have questions or comments, you can send them to me at You may also make corrections to this page.

A (brazilian) portuguese translation is available at thanks to Rodrigo B. Vieira.


We will cover:


You will need:

PyQt works on other systems. This tutorial may or may not work as well. However, I cannot provide all the details on how to get them to work on all the systems that can use PyQt. You are responsible for figuring that out.

You should already know:

If you haven't fulfilled these requirements, you may have some trouble getting the tutorial to work.

Using Qt Designer

First things first. We'll start where I start. Open up a bash prompt. Start Qt Designer by typing the following command:

You are presented with Qt designer. Depending on which version you are running, it may appear slightly different.

I won't assume you are totally inept at using Qt Designer. If you are, you can easily read the documentation.

Create a new widget. Name it 'at_auto'. Add some stuff to it:

Now, rearrange the layout using the Qt layout tools to your heart's content. You may need to use some spacers as well.

Save the file in a project directory for this tutorial. If you haven't already created one, create one called "pyqt_tutorial" or something. Save the file as "at.ui".

Using pyuic

Go back to your bash prompt, or open up a new one. Go into the project directory, and run these commands.

This command will store the generated python code that comes from the Qt ui file into

Everytime we change the ui file, we need to regenerate the file. Let's add this command to a makefile.

/!\ Tabs are important!

Now run the makefile.

Notice that it says something about all the files being up to date. Let's touch at.ui so it appears newer than, and then run make again.

Now it echos out the commands it runs. You see that it has successfully regenerated


The idea here is that you want the GUI developer to be able to go and make changes to the GUI interface (like moving stuff around) without affecting the logic behind the GUI. So with your setup right now, all the GUI developer has to do is use Qt Designer to change the at.ui file, and then run make to see his changed take effect.

Your make file will get more complicated as you add more files. Be sure to read more about make so that you make good design decisions early on about how to use make properly.

Running Your Application

So we have that at.ui file, and the file. How do we actually run the app?

We have to create Here is what it will look like.

Now, run it.

Tada! You have your application.

NOTE: If you are using Qt designer with Qt version 3.3.0 your .ui file contains: <!DOCTYPE UI><UI version="3.3" stdsetdef="1"> in the header, and pyuic (3.8.1 at least) complains that the version is too recent and won't produce any output.

This is easy to solve; you can create a tiny script which will automatically fix this error, run make and run your new application:


sed -i s/3.3/3.3.0/g at.ui


exec python

chmod 700 myscript and you're set !

Setting the Default Date / Time

Let's set a default value for the QDateTimeEdit widget. The QDateTimeEdit widget expects a QDateTime for an argument to the setDateTime method, so we'll have to create one. But how to set the time of the QDateTime? Examination of the documentation reveals that the setTime_t method will allow us to set the date with the time in seconds from the Unix epoch. We can get that from the time() function in the built-in time module.

Here's the code that does that. We'll put this in the __init__ method so that it gets populated correctly from the beginnin. Remember to import time!

This code snippet should show how easily python and PyQt work with each other. It should also demonstrate the thought processes you'll have to go through to manipulate Qt's widgets.

Signals and Slots

Everything you do from here on out is connecting Signals to Slots. It's pretty easy, which is why I like PyQt.

Python isn't C++. So it has to deal with Signals and Slots in a new way.

First, in Python, anything that is callable is a slot. It can be a bound method, a function, or even a lambda expression. Second, in Python, a signal is just some text that is meaningless.

Let me clarify the distinction between a C++ Signal/Slot and a Python Signal/Slot. It has nothing to do with where the object was created. It has everything to do with where the Signal originated, and where the Slot is located. For instance, a QPushButton has a C++ Signal, "clicked()". If you create your own subclass in Python, called "PyPushButton", it still has a C++ Signal, "clicked()". If you created a new Signal in Python, called "GobbledyGook()", then it is a Python Signal, because nothing in C++ even knows of its existence.

When you bind a signal to a slot, you can do one of the following:

Our application is going to respond to only one signal: the "Schedule" button being pressed. What it will do is run the "at" command with appropriate arguments.

Here is the code to initiate the connection:

Notice that we are connecting a C++ Signal to a Python Slot. However, that slot doesn't exist yet. Let's add it to the 'at' class.

The process here is two fold. First, we check to see if something is specified in the "command" QLineEdit widget. If not, we show a QMessageBox with a critical message.

If there is something in the command box, we open up a pipe to the 'at' command. 'at' expects the command to be coming in on stdin. We then write to it's stdin the command we want to execute. Notice that we don't do any error checking here.

Go ahead and run the application now, and use the 'atq' command to see if the 'at' job was queued up.

Good? Okay.

Here is the final code for the '' file.


With the time remaining, you may want to add a few extensions.

Future Directions

This application could be part of a suite of Unix command line interfaces. What other commands would you like to implement? I suggest giving things like "crontab" and "ps" a try. Parsing the output of these commands isn't too difficult, and the interface with them is pretty easy.

You may also want to try and combine your new apps with the 'at' app. If you like, you can sell them as a Unix graphical interface, but you'll have to buy the commercial license for both Qt and PyQt unless you stick with something like the GPL.

JonathanGardnerPyQtTutorial (last edited 2014-04-14 04:47:53 by DaleAthanasias)

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