Multiple QWidgets in the central widget

I'm just starting out with Qt and I'm trying to write an app with an interface, written by hand, not with Qt Designer, that looks like this

but I can't figure out how to add more than one widget to the central widget, and I can't find any documentation or ex开发者_如何学Pythonamples that I could use. Can anyone help me with this?

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I would suggest building your desired interface using QtDesigner and examining the code it generates. You don't have to use QtDesigner in your application, but this will help you to self-educate on how to properly add items, use layout management, etc.