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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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Alessandro Molina Alessandro Molina
Author Profile Icon Alessandro Molina
Alessandro Molina
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Toc

Table of Contents (16) Chapters Close

Preface 1. Containers and Data Structures 2. Text Management FREE CHAPTER 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 15. Other Books You May Enjoy

Time-zone-aware datetime


Python datetimes are usually naive, which means they don't know which time zone they refer to. This can be a major problem because, given a datetime, it's impossible to know when it actually refers to.

The most common error in working with dates in Python is trying to get the current datetime through datetime.datetime.now(), as all datetime methods work with naive dates, it's impossible to know which time that value represents.

How to do it...

Perform the following steps for this recipe:

  1. The only reliable way to retrieve the current datetime is by using datetime.datetime.utcnow(). Independently of where the user is and how the system is configured, it will always return the UTC time. So we need to make it time-zone-aware to be able to decline it to any time zone in the world:
import datetime

def now():
    return datetime.datetime.utcnow().replace(tzinfo=datetime.timezone.utc)
  1. Once we have a time-zone-aware current time, it is possible to convert it to any other time...
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