How to change the size of a Qt widget in code?

Question

Qt

I created my own widget, in which I add other widgets. I would like that when adding, the size of the parent widget increases by 100. How can this be done in the program code?

Answer 1

doc.qt.io/qt-5/layout.html is for adaptability.
And it's just that there are methods for setting the size of widgets, for example resize.