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

Errors in web applications


Usually, when a Python WSGI web application crashes, you get a traceback in the Terminal and an empty path in your browser.

That doesn't make it very easy to debug what's going on and unless you explicitly check your Terminal, it might be easy to miss that your page is not showing up because it actually crashed.

Luckily, the Python standard library provides some basic debugging tools for web applications that make it possible to report crashes into the browser so you can see them and fix them without having to jump away from your browser.

How to do it...

The cgitb module provides tools to format an exception and its traceback as HTML, so we can leverage it to implement a WSGI middleware that can wrap any web application to provide better error reporting in the browser:

import cgitb
import sys

class ErrorMiddleware:
    """Wrap a WSGI application to display errors in the browser"""
    def __init__(self, app):
        self.app = app

    def __call__(self, environ,...