Book Image

Getting Started with Python

By : Fabrizio Romano, Benjamin Baka, Dusty Phillips
Book Image

Getting Started with Python

By: Fabrizio Romano, Benjamin Baka, Dusty Phillips

Overview of this book

This Learning Path helps you get comfortable with the world of Python. It starts with a thorough and practical introduction to Python. You’ll quickly start writing programs, building websites, and working with data by harnessing Python's renowned data science libraries. With the power of linked lists, binary searches, and sorting algorithms, you'll easily create complex data structures, such as graphs, stacks, and queues. After understanding cooperative inheritance, you'll expertly raise, handle, and manipulate exceptions. You will effortlessly integrate the object-oriented and not-so-object-oriented aspects of Python, and create maintainable applications using higher level design patterns. Once you’ve covered core topics, you’ll understand the joy of unit testing and just how easy it is to create unit tests. By the end of this Learning Path, you will have built components that are easy to understand, debug, and can be used across different applications. This Learning Path includes content from the following Packt products: • Learn Python Programming - Second Edition by Fabrizio Romano • Python Data Structures and Algorithms by Benjamin Baka • Python 3 Object-Oriented Programming by Dusty Phillips
Table of Contents (31 chapters)
Title Page
Copyright and Credits
About Packt
Contributors
Preface
8
Stacks and Queues
10
Hashing and Symbol Tables
Index

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...