What does '@reify' do and when should it be used?
pyramid, python
Solution
From the source code documentation:
""" Put the result of a method which uses this (non-data) descriptor decorator in the instance dict after the first call, effectively replacing the decorator with an instance variable."""
A description from from the fuzzy notepad blog sums it up nicely.
It acts like @property, except that the function is only ever called once; after that, the value is cached as a regular attribute. This gives you lazy attribute creation on objects that are meant to be immutable.
So in the code you posted, site_menu can be accesses like a cached property.
Problem
I saw it in the Pyramid tutorial for UX design. I couldn't make out much what this decorator is all about. Sample code where I saw its usage. ``` def __init__(self, request): self.request = request renderer = get_renderer("templates/global_layout.pt") self.global_template = renderer.implementation().macros['layout'] @reify def company_name(self): return COMPANY @reify def site_menu(self): new_menu = SITE_MENU[:] url = self.request.url for menu in new_menu: if menu['title'] == 'Home': menu['current'] = url.endswith('/') else: menu['current'] = url.endswith(menu['href']) return new_menu @view_config(renderer="templates/index.pt") def index_view(self): return {"page_title": "Home"} @view_config(renderer="templates/about.pt", name="about.html") def about_view(self): return {"page_title": "About"} ```