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

Pickling and shelving


If there is a lot of information that your software needs or if you want to preserve history across different runs, there is little choice apart from saving it somewhere and loading it back on the next run.

Manually saving and loading back data can be tedious and error-prone, especially if the data structures are complex.

For this reason, Python provides a very convenient module, shelve, that allows us to save and restore Python objects of any kind as far as it's possible to pickle them.

How to do it...

Perform the following steps for this recipe:

  1. shelf, implemented by shelve, can be opened like any other file in Python. Once opened, it's possible to read and write keys into it like a dictionary:
>>> with shelve.open('/tmp/shelf.db') as shelf:
...   shelf['value'] = 5
...
  1. Values stored into shelf can be read back as a dictionary, too:
>>> with shelve.open('/tmp/shelf.db') as shelf:
...   print(shelf['value'])
... 
5
  1. Complex values, or even custom classes, can...