Book Image

Modern Python Standard Library Cookbook

By : Molina
Book Image

Modern Python Standard Library Cookbook

By: 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 (16 chapters)

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...