Book Image

Python Data Structures and Algorithms

By : Benjamin Baka
Book Image

Python Data Structures and Algorithms

By: Benjamin Baka

Overview of this book

Data structures allow you to organize data in a particular way efficiently. They are critical to any problem, provide a complete solution, and act like reusable code. In this book, you will learn the essential Python data structures and the most common algorithms. With this easy-to-read book, you will be able to understand the power of linked lists, double linked lists, and circular linked lists. You will be able to create complex data structures such as graphs, stacks and queues. We will explore the application of binary searches and binary search trees. You will learn the common techniques and structures used in tasks such as preprocessing, modeling, and transforming data. We will also discuss how to organize your code in a manageable, consistent, and extendable way. The book will explore in detail sorting algorithms such as bubble sort, selection sort, insertion sort, and merge sort. By the end of the book, you will learn how to build components that are easy to understand, debug, and use in different applications.
Table of Contents (20 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
5
Stacks and Queues
7
Hashing and Symbol Tables

Hash table


A hash table is a form of list where elements are accessed by a keyword rather than an index number. At least, this is how the client code will see it. Internally, it will use a slightly modified version of our hashing function in order to find the index position in which the element should be inserted. This gives us fast lookups, since we are using an index number which corresponds to the hash value of the key.

We start by creating a class to hold hash table items. These need to have a key and a value, since our hash table is a key-value store:

    class HashItem: 
        def __init__(self, key, value): 
            self.key = key 
            self.value = value 

This gives us a very simple way to store items. Next, we start working on the hash table class itself. As usual, we start off with a constructor:

    class HashTable: 
        def __init__(self): 
            self.size = 256 
            self.slots = [None for i in range(self.size)] 
            self.count = 0 

The hash...