Lesson 22 — Cache decorator (expert)

Remember slow answers

A decorator is a function that wraps another function to add behaviour; you apply it with @name above the def. A cache decorator stores results by argument, so the second call with the same input skips the slow work. Django has @cache_page for whole views.

if city not in weather:
    weather[city] = fetch(city)   # only the first time
return weather[city]

Note: the exercise runs in your browser without Django installed, so it is a small plain-Python simulation of what Django does for you.

Why it matters: caching is the cheapest way to make a busy page fast.