[Python-Dev] Re: __metaclass__ and __author__ are already decorators

[Bob Ippolito]

On Aug 21, 2004, at 6:54 PM, Paul Morrow wrote:

> Bob Ippolito wrote:
>
>> On Aug 21, 2004, at 6:24 PM, Paul Morrow wrote:
>>>
>>> It seems that writing a decorator is going to be a bizarre 
>>> experience. In the example, I would need to write a function named 
>>> 'decoration' that returns a function that will recieve a function 
>>> (foo) to be decorated and then return a function.  Does that sound 
>>> about right?
>> Yes that is correct.
>>> What would functions like 'decoration' typically look like?  Could 
>>> you show a short code snippet?
>> http://python.org/peps/pep-0318.html
>
> Thanks.  Of the 5 examples there, the first two are apparently not 
> implemented correctly, as they expect that the function/class to be 
> decorated is passed directly to them, rather than to the function they 
> return.  Would you agree?  I pasted them here for your 
> consideration...

No, they are correct.  You are confused.  What is expected is that the 
result of the expression after @ is callable and takes one parameter.  
If the expression after @ is just a name, then nothing particularly 
exciting happens at that time.

@bar # NOTE THE LACK OF PARENTHESES
def foo():
	....

is equivalent to:

_tmp = bar
def foo():
	....
foo = _tmp(foo)

_tmp = bar clearly doesn't do anything special

However, you're confusing that with examples that look more like:

@bar()  # NOTE THE PARENTHESES
def foo():
	....

which are equivalent to:

_tmp = bar()
def foo():
	....
foo = _tmp(foo)

-bob