Decorators & Closures

Decorators 101

** A decorator is a callable that takes another function as argument (the decorated func.)** The decorator may perform some processing with the decorated function, and return it or replaces it with another function or callable object.

Both these code snippet shas the same effect:

@decorate
def target():
    print("running target()")

v/s

## this code snippet has the same effect as the above one (using @decorate decorator)
def target():
    print("running target()")

target = decorate(target)

Decorators are just syntactic sugar. We can always call a decorator like any regular callable, passing another function (as shown in 2^nd snippet above).

1. Decorators have the power to replace the decorated-function with a different one.
2. Decorators are executed immediately when a module is loaded.

When does Python executs decorators?

A key feature of decorators is that they run right after the decorated function is defined. This happens usually at the import time (i.e. when the module is loaded).

An example

## registration.py module
registry = []