Book Image

Secret Recipes of the Python Ninja

Book Image

Secret Recipes of the Python Ninja

Overview of this book

This book covers the unexplored secrets of Python, delve into its depths, and uncover its mysteries. You’ll unearth secrets related to the implementation of the standard library, by looking at how modules actually work. You’ll understand the implementation of collections, decimals, and fraction modules. If you haven’t used decorators, coroutines, and generator functions much before, as you make your way through the recipes, you’ll learn what you’ve been missing out on. We’ll cover internal special methods in detail, so you understand what they are and how they can be used to improve the engineering decisions you make. Next, you’ll explore the CPython interpreter, which is a treasure trove of secret hacks that not many programmers are aware of. We’ll take you through the depths of the PyPy project, where you’ll come across several exciting ways that you can improve speed and concurrency. Finally, we’ll take time to explore the PEPs of the latest versions to discover some interesting hacks.
Table of Contents (17 chapters)
Title Page
Copyright and Credits
Packt Upsell
Foreword
Contributors
Preface
Index

Modifying interactive interpreter startup


As mentioned in the Working with environment variables recipe, the PYTHONSTARTUP environment variable can be set to point to a file that contains commands that run prior to the Python interpreter starting up. This functionality is similar to .profile on *NIX shells.

As this startup file is only examined when interactive mode is used, there is no need to worry about trying to set configurations for running scripts (though later on we will show how to include the startup file in a script). The commands in this file are executed within the same namespace as the interactive interpreter, so there is no need to qualify functions or other imports with dot-nomenclature. This file is also responsible for making changes to interactive prompts: >>> (sys.ps1) and ... (sys.ps2).

How to do it...

  1. To read an additional startup file from the current directory, the following example command shows how to code it in the global startup file (read_startup.py):
 ...