stack = []                           # on first import
error = 'stack2.error'               # local exceptions

def push(obj):                       # no need for 'global'
    stack.append(obj)                # add item to end

def pop():	
    if not stack:
        raise error, 'stack underflow'  # raise local error
    top = stack[-1] 
    del stack[-1]                       # remove last item
    return top

def top():
    if not stack:                       # raise local error
        raise error, 'stack underflow'  # or let IndexError
    return stack[-1] 

def empty():      return not stack           # is the stack []?
def member(obj):  return obj in stack        # item in stack?
def item(offset): return stack[-(offset+1)]  # index the stack
def length():     return len(stack)          # number entries
def dump():       print '<Stack:%s>' % stack