decorators-descriptors | Descriptors Decoded '' PyCon US 2017 Tutorial

decorators-descriptors is a Python library. decorators-descriptors has no bugs, it has no vulnerabilities, it has a Permissive License and it has low support. However decorators-descriptors build file is not available. You can download it from GitHub.

Python developers use decorators and descriptors on a daily basis, but many don't understand them well enough to create (or debug) them. Decorators are widely deployed in popular Python Web frameworks. Descriptors are the key to the database mappers used with those frameworks, but under the covers they play an even more crucial role in Python as the device that turns plain functions into bound methods, setting the value of the self argument. This tutorial is a gentle introduction these important Python features, using a test-driven presentation and exercises. Decorators without closures are presented first, highlighting the difference between run time and import time that is crucial when meta-programming. We then get a firm grounding on closures and how they are implemented in Python, before moving to higher order function decorators. Coverage of descriptors starts with a close look at Python's property built-in function and dynamic attribute look up. We then implement some ORM-like field validation descriptors, encounter a usability problem, and leverage a class decorator to solve the issue. A metaclass appears briefly at the very end to make the solution transparent to our library users, while making the library maintainers life more interesting.