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Modern Python Standard Library Cookbook

You're reading from   Modern Python Standard Library Cookbook Over 100 recipes to fully leverage the features of the standard library in Python

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Product type Paperback
Published in Aug 2018
Publisher Packt
ISBN-13 9781788830829
Length 366 pages
Edition 1st Edition
Languages
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Author (1):
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 Molina Molina
Author Profile Icon Molina
Molina
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Toc

Table of Contents (21) Chapters Close

Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
1. Containers and Data Structures FREE CHAPTER 2. Text Management 3. Command Line 4. Filesystem and Directories 5. Date and Time 6. Read/Write Data 7. Algorithms 8. Cryptography 9. Concurrency 10. Networking 11. Web Development 12. Multimedia 13. Graphical User Interfaces 14. Development Tools 1. Other Books You May Enjoy 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...
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