Book Image

Hands-On Data Structures and Algorithms with Python - Second Edition

By : Dr. Basant Agarwal, Benjamin Baka
Book Image

Hands-On Data Structures and Algorithms with Python - Second Edition

By: Dr. Basant Agarwal, Benjamin Baka

Overview of this book

Data structures allow you to store and organize data efficiently. They are critical to any problem, provide a complete solution, and act like reusable code. Hands-On Data Structures and Algorithms with Python teaches you the essential Python data structures and the most common algorithms for building easy and maintainable applications. This book helps you to understand the power of linked lists, double linked lists, and circular linked lists. You will learn to create complex data structures, such as graphs, stacks, and queues. As you make your way through the chapters, you will explore the application of binary searches and binary search trees, along with learning common techniques and structures used in tasks such as preprocessing, modeling, and transforming data. In the concluding chapters, you will get to grips with organizing your code in a manageable, consistent, and extendable way. You will also study how to bubble sort, selection sort, insertion sort, and merge sort algorithms in detail. By the end of the book, you will have learned how to build components that are easy to understand, debug, and use in different applications. You will get insights into Python implementation of all the important and relevant algorithms.
Table of Contents (16 chapters)

Sorting dictionaries

If we want to do a simple sort on either the keys or values of a dictionary, we can do the following:

>>> d = {'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 'six': 6} 
>>> sorted(list(d))
['five', 'four', 'one', 'six', 'three', 'two']
>>> sorted(list(d.values()))
[1, 2, 3, 4, 5, 6]

Note that the first line in the preceding code sorts the keys alphabetically and the second line sorts the values in order of the integer value.

The sorted() method has two optional arguments that are of interest: key and reverse. The key argument has nothing to do with the dictionary keys, but rather is a way of passing a function to the sort algorithm to determine the sort order. For example, in the following code, we use the...