pdb & stack dumping

import pdb
import sys
import traceback

class nob:
    def __init__(self):
        self.D = bytearray(b'', 'utf-8')

    def R(self, r):
        self.D.extend(r)

    def L(self, l):
        if(l <= len(self.D)):
            return self.D[l-1]

    def A(self, a):
        if(a < len(self.D)):
            return(self.D[-a:])
        elif(a == len(self.D)):
            return(self.D)
        else:
            exit(0)

def excepthook(type, value, tb):
    print "*** print_stack:"
    traceback.print_stack()
    pdb.set_trace()

try:
    sys.excepthook = excepthook
    print(dir(traceback))
    Nob = nob()
    Nob.R('D')
    Nob.D.extend(Nob.D)
    print(Nob.L(3))
    print(Nob.A(1))
except Exception as err:
    exc_type, exc_value, exc_traceback = sys.exc_info()
    print "*** print_tb:"
    traceback.print_tb(exc_traceback, limit=1, file=sys.stdout)
    print "*** print_exception:"
    traceback.print_exception(exc_type, exc_value, exc_traceback,
                              limit=2, file=sys.stdout)
    print "*** print_exc:"
    traceback.print_exc()
    print "*** format_exc, first and last line:"
    formatted_lines = traceback.format_exc().splitlines()
    print formatted_lines[0]
    print formatted_lines[-1]
    print "*** format_exception:"
    print repr(traceback.format_exception(exc_type, exc_value,
                                          exc_traceback))
    print "*** extract_tb:"
    print repr(traceback.extract_tb(exc_traceback))
    print "*** format_tb:"
    print repr(traceback.format_tb(exc_traceback))
    print "*** tb_lineno:", exc_traceback.tb_lineno
    pdb.set_trace()