# module stack stack = [] def init(): global stack stack = [] def push(data): global stack stack.append(data) def pop(): global stack x = stack[-1] del stack[-1] return x def isEmpty(): global stack return not stack >>> import stack1 >>> stack1.push(1) >>> stack1.push(2) >>> stack1.push(3) >>> stack1.stack [1, 2, 3] >>> stack1.pop() 3 >>> stack1.stack [1, 2] >>> stack1.isEmpty() 0 >>> stack1.init(