the following snippet:

%pdb 1
def foo(x=5):
    if x < 0:
        raise ValueError('foo')
    else:
        return foo(x-1)
foo()

Leads to the following screenshot,

Oops, the raw_input should be last.... Not sure if it's a IPython thing to fix, or a notebook one where we should make sure the raw-input is always last in a cell.