Python decorator? - can someone please explain this?

Question

Apologies this is a very broad question.

The code below is a fragment of something found on the web. The key thing I am interested in is the line beginning @protect

Answer 1

The decorator syntax:

@protected(check_valid_user) 
def do_upload_ajax():
    "..."

is equivalent to

def do_upload_ajax():
    "..."
do_upload_ajax = protected(check_valid_user)(do_upload_ajax)

but without the need to repeat the same name three times. There is nothing more to it.

For example, here's a possible implementation of protected():

import functools

def protected(check):
    def decorator(func): # it is called with a function to be decorated
        @functools.wraps(func) # preserve original name, docstring, etc
        def wrapper(*args, **kwargs):
            check(bottle.request) # raise an exception if the check fails
            return func(*args, **kwargs) # call the original function
        return wrapper # this will be assigned to the decorated name
    return decorator