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Re: I love the decorator in Python!!!

From K.-Michael Aye <kmichael.aye@gmail.com>
Subject Re: I love the decorator in Python!!!
Date 2011-12-08 17:24 +0100
Organization University of Bern
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Newsgroups comp.lang.python
Message-ID <mailman.3428.1323361468.27778.python-list@python.org> (permalink)

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On 2011-12-08 11:43:12 +0000, Chris Angelico said:

> On Thu, Dec 8, 2011 at 10:22 PM, K.-Michael Aye <kmichael.aye@gmail.com> wrote:
>> I am still perplexed about decorators though, am happily using Python for
>> many years without them, but maybe i am missing something?
>> For example in the above case, if I want the names attached to each other
>> with a comma, why wouldn't I just create a function doing exactly this? Why
>> would I first write a single name generator and then decorate it so that I
>> never can get single names anymore (this is the case, isn't it? Once
>> decorated, I can not get the original behaviour of the function anymore.
> 
> The example given is a toy. It's hardly useful. However, there are a
> number of handy uses for decorators; mostly, they consist of giving a
> single simple keyword to a complicated set of logic. One example is
> the @classmethod and @staticmethod decorators - the code to implement
> them could be uglier than nested inline assembly, but you don't have
> to care, because you just type "@staticmethod" in front of your def
> statement and it does its magic.
> 
> Here's a handy trick that I'm sure someone has done in a more 
> sophisticated way:
> 
> def trace(func):
>     if debugmode:
>         return lambda *a,**ka:
> (print(">"+func.__name__),func(*a,**ka),print("<"+func.__name__))[1]
>     return func
> 
> Then you put @trace in front of all your functions, and if debugmode
> is False, nothing will be done - but set it to true, and you get
> console output at the entry and exit of each function.
> 
>>>> @trace
> def test(x):
> 	print("Test! "+x)
> 	return 5
> 
>>>> test("asdf")
>> test
> Test! asdf
> <test
> 5
> 
> Again, it's helpful because it condenses all the logic (including the
> 'debugmode' flag) down to a single high level directive: "Trace this
> function".
> 
> ChrisA

I understand this one, it seems really useful. And maybe i start to 
sense some more applicability. Like this, with extra flags that could 
be set at run time, I could influence the way a function is executed 
without designing the function too complex, but by decorating it, which 
at the end could be easier to read than complicated if-then statements 
in the function.
Thanks for your example.
Michael

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Thread

I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-07 23:18 -0800
  Re: I love the decorator in Python!!! Chris Rebert <clp2@rebertia.com> - 2011-12-08 00:04 -0800
  Re: I love the decorator in Python!!! Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-12-08 09:59 +0100
    Re: I love the decorator in Python!!! Chris Angelico <rosuav@gmail.com> - 2011-12-08 20:37 +1100
    Re: I love the decorator in Python!!! K.-Michael Aye <kmichael.aye@gmail.com> - 2011-12-08 12:22 +0100
      Re: I love the decorator in Python!!! Francesco Bochicchio <bieffe62@gmail.com> - 2011-12-09 04:00 -0800
    Re: I love the decorator in Python!!! Chris Angelico <rosuav@gmail.com> - 2011-12-08 22:43 +1100
      Re: I love the decorator in Python!!! Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-12-09 10:57 +0100
      Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-09 10:28 -0800
        Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-09 16:21 -0800
        Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-09 16:21 -0800
          Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-10 06:04 -0800
            Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-10 06:09 -0800
              Re: I love the decorator in Python!!! alex23 <wuwei23@gmail.com> - 2011-12-11 19:35 -0800
            Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-10 06:09 -0800
          Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-10 06:04 -0800
      Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-09 10:28 -0800
    Re: I love the decorator in Python!!! K.-Michael Aye <kmichael.aye@gmail.com> - 2011-12-08 17:24 +0100
    Re: I love the decorator in Python!!! Chris Angelico <rosuav@gmail.com> - 2011-12-09 03:38 +1100
      Re: I love the decorator in Python!!! alex23 <wuwei23@gmail.com> - 2011-12-08 21:02 -0800
        Re: I love the decorator in Python!!! Robert Kern <robert.kern@gmail.com> - 2011-12-09 10:08 +0000
          Re: I love the decorator in Python!!! alex23 <wuwei23@gmail.com> - 2011-12-11 19:36 -0800
            Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-11 20:51 -0800
              Re: I love the decorator in Python!!! alex23 <wuwei23@gmail.com> - 2011-12-11 21:47 -0800
                Re: I love the decorator in Python!!! 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-12 04:16 -0800
            Re: I love the decorator in Python!!! Ethan Furman <ethan@stoneleaf.us> - 2011-12-11 23:47 -0800
            Re: I love the decorator in Python!!! Robert Kern <robert.kern@gmail.com> - 2011-12-12 16:27 +0000
              Re: I love the decorator in Python!!! alex23 <wuwei23@gmail.com> - 2011-12-12 16:46 -0800
    Re: I love the decorator in Python!!! Andrew Berg <bahamutzero8825@gmail.com> - 2011-12-08 10:54 -0600
    Re: I love the decorator in Python!!! Andrew Berg <bahamutzero8825@gmail.com> - 2011-12-08 10:55 -0600
    Re: I love the decorator in Python!!! Ethan Furman <ethan@stoneleaf.us> - 2011-12-08 15:34 -0800
    Re: I love the decorator in Python!!! Ethan Furman <ethan@stoneleaf.us> - 2011-12-08 15:56 -0800

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