|
Data Structures and Algorithms
with Object-Oriented Design Patterns in Python |
Program 
defines the __iter__ method
of the StackAsLinkedList class.
The __iter__ method returns an instance
of the nested class StackAsLinkedlist.Iterator
that implements the iterator protocol (lines 3-16).
Program: StackAsLinkedList class __iter__ method.
The Iterator class has two instance attributes, _container and _position. The _container instance attribute refers to the stack whose elements are being enumerated. The _position instance attribute is used to keep track of the position in the linked list of the next object to be enumerated.
The purpose of the _next method is
to advance the iterator to the next object in the stack
and to raise a StopIteration exception
when there are no more elements to be enumerated.
In Program elements remain as long as
the _position is not None.
Clearly, the running time of _next is O(1).
Copyright © 2003, 2004 by Bruno R. Preiss, P.Eng. All rights reserved.