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

Safely replacing file's content


Replacing the content of a file is a very slow operation. Compared to replacing the content of a variable, it's usually a few times slower; when we write something to disk, it takes time before it's actually flushed and time before the content is actually written to disk. It's not an atomic operation, so if our software faces any issues while saving a file, there is a good chance that the file might end up being half-written and our users don't have a way to recover the consistent state of their data.

There is a pattern commonly used to solve this kind of issue, which is based on the fact that writing a file is a slow, expensive, error-prone operation, but renaming a file is an atomic, fast, and cheap operation.

How to do it...

You need to perform the following recipes:

  1. Much like open can be used as a context manager, we can easily roll out a safe_open function that allows us to open a file for writing in a safe way:
import tempfile, os

class safe_open:
    def...