Path: csiph.com!usenet.pasdenom.info!gegeweb.org!usenet-fr.net!nerim.net!novso.com!newsfeed.xs4all.nl!newsfeed1.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.017 X-Spam-Evidence: '*H*': 0.97; '*S*': 0.00; 'explicitly': 0.05; 'arguments': 0.09; 'decorator': 0.09; 'subject:Function': 0.09; 'variables.': 0.09; 'def': 0.12; '**kwargs)': 0.16; '**kwargs):': 0.16; 'class:': 0.16; 'complicated,': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'levels,': 0.16; 'nesting': 0.16; 'referencing': 0.16; 'repetition': 0.16; 'scope,': 0.16; 'wrote:': 0.18; 'to:name:python-list@python.org': 0.22; 'mon,': 0.24; 'header:In-Reply-To:1': 0.27; 'function': 0.29; 'message-id:@mail.gmail.com': 0.30; "i'm": 0.30; 'class': 0.32; 'skip:_ 10': 0.34; 'received:google.com': 0.35; 'really': 0.36; 'method': 0.36; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'sure': 0.39; 'to:addr:python.org': 0.39; 'even': 0.60; 'simple': 0.61; 'skip:n 10': 0.64; 'more': 0.64; 'gain': 0.79; '2015': 0.84; 'ethan': 0.84; 'furman': 0.84; 'n):': 0.84; 'self.n': 0.84; 'capture': 0.91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=myhBfyqI6i10WIti7aXfPsnLc8flHLJ1V6NM7W9LIAQ=; b=ynwfhtTKxUKlRKjyKPA9F9ALR1cJH/vCmK91AJ0+dhomUOglMNf36EoG44kW2JVVMm L6HQV+fm4LFdrOGoJX7YvWSgjUodR0MUyrTUnKV6sTAk6awgyZwJy5VrcPf+ahJMU8a1 qb1Xymwgihh35xrvkhAdCQ/me2D1LDOiC/p4Yeed7myy7P49Ji5sXODDo89BiQo4/qOy EYKx8jVv+ptg3r8+143OofoDdNTvRxrl6qty5a0LEw9MJCFe0w98iN7RtQFW4z+FVlfM 0iOKSoiUPBXOjS8n4+YSOkjbk7Tg/0WFss+yxFB3m9RT+luPyeMsm9Z5JlsMsS3X+2hu EAqA== MIME-Version: 1.0 X-Received: by 10.50.176.137 with SMTP id ci9mr11169891igc.2.1430109125414; Sun, 26 Apr 2015 21:32:05 -0700 (PDT) In-Reply-To: <20150427042426.GD32422@stoneleaf.us> References: <20150427042426.GD32422@stoneleaf.us> Date: Mon, 27 Apr 2015 14:32:05 +1000 Subject: Re: Function decorator having arguments is complicated From: Chris Angelico To: "python-list@python.org" Content-Type: text/plain; charset=UTF-8 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 35 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1430109133 news.xs4all.nl 2920 [2001:888:2000:d::a6]:44740 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:89441 On Mon, Apr 27, 2015 at 2:24 PM, Ethan Furman wrote: > On 04/27, Makoto Kuwata wrote: >> >> I feel that function decorator having arguments is complicated, >> because three 'def' are nested: >> >> def multiply(n): >> def deco(func): >> def newfunc(*args, **kwargs): >> return n * func(*args, **kwargs) >> return newfunc >> return deco > > When I have to write an argument-taking decorator, I use a class: > > class multiply(object): # don't need 'object in 3.x' > > def __init__(self, n): > self.n = n > > def __call__(self, func): > def newfunc(*args, **kwargs): > return self.n * func(*args, **kwargs) > return newfunc What's the advantage of that over a simple closure? You have the same number of nesting levels, plus a lot more boiler-plate repetition - instead of just referencing names from the outer scope, you have to explicitly capture them all with "self.n=n" for each one. I'm not sure you really even gain much clarity. In a way, a closure is a short-hand for an object with a __call__ method that auto-captures all its local variables. ChrisA