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

Applying variable context managers


When using context managers, you must rely on the with statement to apply them. While it's possible to apply more than one context manager per statement by separating them with commas, it's not as easy to apply a variable number of them:

@contextlib.contextmanager
def first():
    print('First')
    yield

@contextlib.contextmanager
def second():
    print('Second')
    yield

The context managers that we want to apply must be known when writing the code:

>>> with first(), second():
>>>     print('Inside')
First
Second
Inside

But what if sometimes we only want to apply the first context manager, and sometimes we want to apply both?

How to do it...

contextlib.ExitStack serves various purposes, one of which is to allow us to apply a variable number of context managers to a block.

For example, we might want to apply both context managers only when we are printing an even number in a loop:

from contextlib import ExitStack

for n in range(5):
    with...