Werkzeug - The comprehensive WSGI web application library

Werkzeug started as a simple collection of various utilities for WSGI applications and has become one of the most advanced WSGI utility modules. It includes a powerful debugger, fully featured request and response objects, HTTP utilities to handle entity tags, cache control headers, HTTP dates, cookie handling, file uploads, a powerful URL routing system and a bunch of community contributed addon modules.

Werkzeug is the base of frameworks such as Flask and more, as well as in house frameworks developed for commercial products and websites.