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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

Verifying a file's integrity


If you've ever downloaded a file from a public network, you might have noticed that their URLs are frequently in the form of http://files.host.com/somefile.tar.gz#md5=3b3f5b2327421800ef00c38ab5ad81a6.

That's because the download might go wrong and the data you got might be partially corrupted. So the URL includes an MD5 hash that you can use to verify that the downloaded file is fine through the md5sum tool.

The same applies when you download a file from a Python script. If the file provided has an MD5 hash for verification, you might want to check whether the retrieved file is valid and, in cases where it is not, then you can retry downloading it again.

How to do it...

Within hashlib, there are multiple supported hashing algorithms, and probably the most widespread one is md5, so we can rely on hashlib to verify our downloaded file:

import hashlib

def verify_file(filepath, expectedhash, hashtype='md5'):
    with open(filepath, 'rb') as f:
        try:
         ...
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