[Python-Dev] Re: __metaclass__ and __author__ are already
decorators
Bob Ippolito
bob at redivi.com
Sun Aug 22 01:11:12 CEST 2004
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
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