import sys

def printTrace(frame, event, arg):
    if (event == 'exception'):
        print arg
        print 'Arg size=', len(arg)
        print arg[2]
    return printTrace

def foo():
    print 'Here foo'
   
sys.settrace(printTrace)
foo()

import threading

try:
    dir(pippo)
except:
    print "Error caught"