[Python-Dev] Re: method decorators (PEP 318) (original) (raw)

Robert Mollitor mollitor at earthlink.net
Sun Mar 28 18:27:19 EST 2004

On Sunday, March 28, 2004, at 04:38 PM, Skip Montanaro wrote:

Robert> My point here is we may want to aim for making the information Robert> kept on the function object itself as rich as possible and make Robert> the "decorations" do the work of pulling information from Robert> whatever the function "publishes". You can do that with just the decorator syntax: def attrs(**kwds): def setattributes(f): for k in kwds: setattr(f, k, kwds[k]) return f return setattributes def func(arg1, arg2) [attrs(accepts=(int, (int,float)), returns=((int,float))), checktypes]: pass

Upon which object are the attributes set in each of the following cases?

def cm(cls,arg1, arg2) [attrs(accepts=(int, (int,float)),

returns=((int,float))), check_types, classmethod]: pass

def cm(cls,arg1, arg2) [classmethod, attrs(accepts=(int, (int,float)),

returns=((int,float))), check_types]: pass

classmethod(cm).foo = "abc" is currently disallowed, and if it wasn't, we would need to somehow redirect things so 'foo' is placed in the original 'cm' function object's dict, no?

Even ignoring classmethod/staticmethod, what is the docstring of 'func' after you do

def printout(f):
    def new_f(*args, **kwds):
        print "Running f"
        return f(*args, **kwds)
    return new_f

def func(arg1, arg2) [printout]:
    """My function."""
    print "Inside f"

That is, what would "help(func)" generate?

Robert> ... there is a trivial workaround if we restrict the transformer Robert> list to identifiers:

Robert> sync = synchronized(lockattr="baz") Robert> def func [sync] (arg1, arg2): Robert> pass I think restricting decorators to only be identifiers would be shortsighted. I can understand having to create workarounds for unforseen situations, but it's clear at this point in the discussion that decorator functions might need to accept parameters. Why not let them?

It is easier to expand a public grammar than it is to shrink one.

Robert Mollitor

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