demo of multiple levels of decorator unwrapping with __wrapped__ attribute

wrapped.py

from functools import wraps

def w(func):
    print("wrapping")
    @wraps(func)
    def wrapper(*args, **kwargs):
        print("I'm inside the wrapper")
        result = func(*args, **kwargs)
        print("leaving the wrapper")
        return result
    return wrapper

@w
@w
@w
def foo():
    print("in foo")

if __name__ == "__main__":
    foo()
    foo.__wrapped__()
    foo.__wrapped__.__wrapped__()
    foo.__wrapped__.__wrapped__.__wrapped__()

This functionality exists in Python 3.4+ (verified on 3.6), but does not exist on Python 2.x.