Decorators

Python · Intermediate

Definition

A decorator is a function that wraps another function to add behavior without changing its code.

Used for logging, timing, caching and access checks.

Diagram

Flowchart

Example: Logging decorator

def log(fn):
    def wrap(*a):
        print('calling', fn.__name__)
        return fn(*a)
    return wrap
@log
def add(x, y): return x + y
print(add(2, 3))

Output: calling add 5

Key points

Use functools.wraps to keep the name
functools.lru_cache is a built-in decorator

Interview questions

What is lru_cache?

A decorator that memoizes function results by arguments.