Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsreader4.netcologne.de!news.netcologne.de!bcyclone04.am1.xlned.com!bcyclone04.am1.xlned.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: <python-python-list@m.gmane.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.014
X-Spam-Evidence: '*H*': 0.97; '*S*': 0.00; 'python3': 0.07; 'received:151': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:skip:c 10': 0.09; '10000000': 0.16; 'comp': 0.16; 'dict': 0.16; 'emanuele': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'seems': 0.21; 'header:User-Agent:1': 0.23; 'header:X-Complaints- To:1': 0.27; 'function': 0.29; 'writes:': 0.31; 'call.': 0.33; 'there': 0.35; 'subject:?': 0.36; 'should': 0.36; 'to:addr:python- list': 0.38; 'does': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'che': 0.60; 'taking': 0.65; 'account?': 0.68; 'sound': 0.68; 'faster.': 0.84; 'quando': 0.84; 'factors': 0.97
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Lele Gaifax <lele@metapensiero.it>
Subject: Re: Dict comprehensions - improvement to docs?
Date: Tue, 17 Mar 2015 15:06:08 +0100
Organization: Nautilus Entertainments
References: <mailman.410.1426483550.21433.python-list@python.org> <87fv95fom0.fsf@jester.gateway.sonic.net> <mailman.427.1426494675.21433.python-list@python.org> <87wq2hfibu.fsf@jester.gateway.sonic.net> <me664q$hon$1@ger.gmane.org> <CALwzid=u19YMkfJBhbLZi1qh2U9UK4ohY5wco1zO-i3T5AtyOA@mail.gmail.com> <me8ige$kjp$1@ger.gmane.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
X-Gmane-NNTP-Posting-Host: 151.62.17.65
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.91 (gnu/linux)
Cancel-Lock: sha1:xvr3OZqcSnDEjqZNN46BW6F8fvs=
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.19
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.495.1426601188.21433.python-list@python.org>
Lines: 20
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1426601188 news.xs4all.nl 2934 [2001:888:2000:d::a6]:60826
X-Complaints-To: abuse@xs4all.nl
X-Received-Bytes: 3472
X-Received-Body-CRC: 3154978226
Xref: csiph.com comp.lang.python:87637

"Frank Millman" <frank@chagford.com> writes:

> It seems that a dict comp is noticeably faster.
>
> Does this sound right, or are there other factors I should be taking into 
> account?

The dict comp does not execute any function call. Consider the following:

    $ python3 -m timeit "d=dict()"
    10000000 loops, best of 3: 0.113 usec per loop
    $ python3 -m timeit "d={}"
    10000000 loops, best of 3: 0.0601 usec per loop

ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.