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Newsgroups: comp.lang.python
Date: Tue, 18 Sep 2012 16:47:44 -0700 (PDT)
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Subject: Re: Decorators not worth the effort
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Xref: csiph.com comp.lang.python:29456

Terry Reedy=E6=96=BC 2012=E5=B9=B49=E6=9C=8815=E6=97=A5=E6=98=9F=E6=9C=9F=
=E5=85=ADUTC+8=E4=B8=8A=E5=8D=884=E6=99=8240=E5=88=8632=E7=A7=92=E5=AF=AB=
=E9=81=93=EF=BC=9A
> 2nd try, hit send button by mistake before
>=20
>=20
>=20
> On 9/14/2012 5:28 AM, Jean-Michel Pichavant wrote:
>=20
>=20
>=20
> > Decorators are very popular so I kinda already know that the fault is
>=20
> > mine. Now to the reason why I have troubles writing them, I don't
>=20
> > know. Every time I did use decorators, I spent way too much time
>=20
> > writing it (and debugging it).
>=20
>=20
>=20
> You are writing parameterized decorators, which require inverted=20
>=20
> currying of the wrapper maker. Perhaps that is why you have trouble. As=
=20
>=20
> I showed in response to Cameron, it may be easier to avoid that by using=
=20
>=20
> a traditional post-def wrapping call instead of decorator syntax.
>=20
>=20
> =20
> --=20
>=20
> Terry Jan Reedy

I'll give another example to show the decorators in python in
versions above 2.4 .

# a general function with the variable input : def  fname( *argc,  **argn)
# a deco is a mapping from an input  funtion to another  function

def deco( fn, *list_in, **dict_in): # use list_in and dict_in to modify fn
    """ deco wrapper """ # deco.__doc__=20

    #print list_in, dict_in, " in the deco"
=20
    def wrapper( fn, *argc, **argan): # to be returned as a function
       # do things one wants before calling fn=20
       result=3Dfn(*argc, **argn)  # call the original, save the result
       # do things after calling fn  =20
       return result=20
    # enhance the  wrapper and get info of fn
    wrapper.__doc__=3Dfn.__doc__
    # enhance wrapper with result, fn, list_in, dict_in
    #....
     return wrapper

def f1():
   """ doc of f1"""
   print "inside f1"

f2=3Ddeco(f1, 2,3,4,5,6, MSG=3D"deco f1 to f2")

f2() # invoke the decorated function from f1


# For a deco maps a deco to another deco  can be done similarly