Fedora 30 : Introduction to Qt Designer.

Qt Designer is the Qt tool for designing and building graphical user interfaces (GUIs) with Qt Widgets... see the Qt Designer manual webpage.

[root@desk mythcat]# dnf install qt5-designer.x86_64
...
Installed:
  qt5-designer-5.12.5-1.fc30.x86_64                                             
  qt5-qttools-libs-designercomponents-5.12.5-1.fc30.x86_64                      

Complete!

Let's start this tool with this command:

[mythcat@desk ~]$ designer-qt5 

Follow this video tutorial from my youtube channel:

You can preview your work with Ctrl+R keys.
After you finish with the project then save the file with this name: mytest.ui.
The next command to create your working python file named mytest.py.
Use this command with the -x option creates the main section to the my.py file that will allow us to test quickly whether the GUI looks as we intended.

[mythcat@desk ~]$ pyuic5 -x  mytest.ui -o mytest.py

Now you can run it to see the output:

[mythcat@desk ~]$ python3  mytest.py