lists and pointer structures you will have already seen lists in python they are convenient and powerful normallyany time you need to store something in listyou use python' built-in list implementation in this howeverwe are more interested in understanding how lists work so we are going to study list internals as you will noticethere are different types of lists python' list implementation is designed to be powerful and to encompass several different use cases we are going to be bit more strict in our definition of what list is the concept of node is very important to lists we shall discuss them in this but this concept willin different formscome back throughout the rest of the book the focus of this will be the followingunderstand pointers in python treating the concept of nodes implementing singlydoublyand circularly linked lists in this we are going to deal quite bit with pointers so it may be useful to remind ourselves what these are to begin withimagine that you have house that you want to sell lacking timeyou contact an agent to find interested buyers so you pick up your house and take it over to the agentwho will in turn carry the house to anybody who may want to buy it ludicrousyou saynow imagine that you have few python functions that work with images so you pass high-resolution image data between your functions of courseyou don' carry your house around what you would do is write the address of the house down on piece of scrap paper and hand it over to the agent the house remains where it isbut the note containing the directions to the house is passed around you might even write it down on several pieces of paper each one is small enough to fit in your walletbut they all point to the same house