This is gonna be a short one: If you want to trigger the ipdb and set breakpoints within the ipython notebook the following won’t work: import ipdb; ipdb.set_trace()

It will get you to the interactive debugger, but you won’t be able to do anything, e.g. print variables etc. (At least this was the case the last time I tried it).

Fortunately, you will get a working interactive debugger session by importing and calling the Tracer as described below (and also in this SO post):

from IPython.core.debugger import Tracer
def fobar(n):
    x = 1337
    y = x + n
    Tracer()() #this one triggers the debugger
    return y

fobar(3)

As a quick reference for the debugger commands available I can warmly recommend the pdb cheatsheet by nblock.