About reading Python code

[WaterWalk]

Hello. I wonder what's the effective way of figuring out how a piece
of python code works. With C I often find it very useful to be able to
run the code in step mode and set breakpoints in a debugger so I can
watch how the it executes, how the data change and how the code jumps
from one function to another. But with Python, the debugger is a
little primitive. The default IDLE doesn't even allow me to set a
breakpoint. When the code is long, I am often lost in it.

So I'm curious how to read code effectively. I agree that python code
is clear, but when it becomes long, reading it can still be a hard
work.