How to resize widgets in layout?

Question

PyQt

I decided to make myself a handy guide to the SI library with blackjack, search and pretty ladies. I have implemented almost all the functionality, there is a "little thing" that I don't know how to do, namely resizing the widgets.
Here's how I did it: I placed a horizontalLayout on the form, and put QTreeView and QTextBrowser into it. I need to change the size of QTreeView and QTextBrowser with the mouse, but I have no idea where to dig. The only thought that comes to mind is to catch events, do a bunch of different calculations and, depending on them, change the size. But something tells me it's fun cycling. Attached the skin of what I want: