Decorators

A decorator is just a function that takes a function and returns a (usually wrapped) function.

The anatomy

@timed          # syntactic sugar for: fib = timed(fib)
def fib(n): ...

@wraps(fn) from functools preserves the original function's name and docstring on the wrapper.

Common uses

• Logging / timing
• Caching (@functools.lru_cache)
• Authentication checks
• Retry logic

Try it

1. Add an @functools.lru_cache(maxsize=None) above @timed and watch fib(30) get instant.
2. Write a @retry(times=3) decorator factory that retries on exceptions.