Book Image

Modern Python Standard Library Cookbook

By : Alessandro Molina
Book Image

Modern Python Standard Library Cookbook

By: Alessandro Molina

Overview of this book

The Python 3 Standard Library is a vast array of modules that you can use for developing various kinds of applications. It contains an exhaustive list of libraries, and this book will help you choose the best one to address specific programming problems in Python. The Modern Python Standard Library Cookbook begins with recipes on containers and data structures and guides you in performing effective text management in Python. You will find Python recipes for command-line operations, networking, filesystems and directories, and concurrent execution. You will learn about Python security essentials in Python and get to grips with various development tools for debugging, benchmarking, inspection, error reporting, and tracing. The book includes recipes to help you create graphical user interfaces for your application. You will learn to work with multimedia components and perform mathematical operations on date and time. The recipes will also show you how to deploy different searching and sorting algorithms on your data. By the end of the book, you will have acquired the skills needed to write clean code in Python and develop applications that meet your needs.
Table of Contents (21 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Producing permutations and combinations


Given a set of elements, if you ever felt the need to do something for each possible permutation of those elements, you might have wondered what the best way to generate all those permutations was.

Python has various functions in the itertools module that will help with permutations and combinations, the differences between those are not always easy to grasp, but once you investigate what they do, they will become clear.

How to do it...

The Cartesian product is usually what people think of when talking about combinations and permutations.

  1. Given a set of elements, A, B, and C, we want to extract all possible couples of two elements, AA, AB, AC, and so on:
>>> import itertools
>>> c = itertools.product(('A', 'B', 'C'), repeat=2)
>>> list(c)
[('A', 'A'), ('A', 'B'), ('A', 'C'),
 ('B', 'A'), ('B', 'B'), ('B', 'C'), 
 ('C', 'A'), ('C', 'B'), ('C', 'C')]
  1. In case you want to omit the duplicated entries (AA, BB, CC), you can just use permutations...