The main benefits of layout is that you get stable arrangements.
Space requirements of UI elements can change, e.g. due to different font or font sizes, language, etc.
Layouts make sure that elements are resized and repositioned as needed.
The usual workflow is to layout items together that belong together, by selecting them and then selecting the approriate layout.
A container widget's main layout is then often just a vertical or horizontal arrangement of these sub layouts.
The UIC is a tool from Qt in your case PyQt. I generates code from the XML document that QtDesigner saves to.
Check the path, see if the executable is there.
There are different approaches.
Usually the class generated by uic is imported and then used inside a user defined class, but is is also possible to derive from the generated class.
Cheers,
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