File: class/Workbook/Exercises/Lab5/stack1.py
stack = [] # on first import error = 'stack1.error' # local exceptions def push(obj): global stack # 'global' to change stack = [obj] + stack # add item to front def pop(): global stack if not stack: raise error, 'stack underflow' # raise local error top, stack = stack[0], stack[1:] # remove front item return top def top(): if not stack: # raise local error raise error, 'stack underflow' # or let IndexError return stack[0] def empty(): return not stack # is the stack []? def member(obj): return obj in stack # item in stack? def item(offset): return stack[offset] # index the stack def length(): return len(stack) # number entries def dump(): print '<Stack:%s>' % stack