[Python-Dev] metaclass and author are already decorators (original) (raw)

Phillip J. Eby pje at telecommunity.com
Sat Aug 21 18:54:37 CEST 2004

At 12:29 PM 8/21/04 -0400, Paul Morrow wrote:

[I posted this on comp.lang.python.general but I'm not sure how many of the folks here read that newsgroup, so my apologies if you're seeing this twice.]

Thinking about decorators, and looking at what we are already doing in our Python code, it seems that metaclass, author, version, etc. are all examples of decorators. So we already have a decorator syntax.

The items you describe are not decorators, they are attributes. The current syntax for decorators is 'x = decorator(x)'.

def baz(self, a, b): """ This describes the baz method. """ synchronized = True returns = None author = 'Neville Shunt' # body of baz goes here...

This syntax already has a different and conflicting meaning in today's Python. A different such syntax:

 [synchronized(), returns(None), author("Neville Shunt")]
 def baz(self, a, b):
     """ This describes the baz method. """
     # body of baz goes here...

has already been rejected on the basis that this too has meaning in today's Python, and that the syntax produces "spooky action at a distance". That is, it's "magical" that the function calls affect the definition below.

Following this logic, expecting assignments to magic names contained within a function's body to magically invoke decorator functions with different names before and outside the block where those names are assigned to in the code, seems far less likely to be considered acceptable.

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