What is PyQt's equivalent to tkinter's canvas?
I think what you need here is QPainter class, Quoting from PyQt Sourceforge documentation:
The QPainter class performs low-level painting on widgets and other paint devices.
QPainter provides highly optimized functions to do most of the drawing GUI programs require. It can draw everything from simple lines to complex shapes like pies and chords. It can also draw aligned text and pixmaps. Normally, it draws in a "natural" coordinate system, but it can also do view and world transformation. QPainter can operate on any object that inherits the QPaintDevice class.