class Test(Exception):
    pass

def traceback_list(tb):
    result = list()
    while True:
        result.append(tb)
        if tb is None:
            break
        tb = tb.tb_next
    return result

try:
    a = Test("thing1")
    print("a.__traceback__ before raise :", traceback_list(a.__traceback__))
    raise a
except Exception as a:
    print("a.__traceback__ after raise :", traceback_list(a.__traceback__))
    try:
        b = Test("thing2").with_traceback(a.__traceback__)
        tracebacks = traceback_list(b.__traceback__)
        print("b.__traceback__ before raise :", tracebacks)
        raise b from a
    except Exception as b:
        tracebacks = traceback_list(b.__traceback__)
        print("b.__traceback__ after raise :", tracebacks)

# produces output like:
# a.__traceback__ before raise : [None]
# a.__traceback__ after raise : [<traceback object at 0xb6fb3b1c>, None]
# b.__traceback__ before raise : [<traceback object at 0xb6fb3b1c>, None]
# b.__traceback__ after raise : [<traceback object at 0xb6fb3b44>, <traceback
#     object at 0xb6fb3b1c>, None]