Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed1.news.xs4all.nl!xs4all!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 0.008
X-Spam-Evidence: '*H*': 0.98; '*S*': 0.00; '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; 'python': 0.11; 'wrote': 0.14; 'dict': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'skip:[ 40': 0.16; 'bit': 0.19; 'header:X-Complaints-To:1': 0.27; 'code': 0.31; '100000': 0.31; 'writes:': 0.31; 'quite': 0.32; 'but': 0.35; 'format.': 0.36; 'subject:?': 0.36; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'frank': 0.68; 'felt': 0.74; 'skip:n 40': 0.81
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: "Frank Millman" <frank@chagford.com>
Subject: Re: Dict comprehensions - improvement to docs?
Date: Mon, 16 Mar 2015 10:30:50 +0200
References: <mailman.410.1426483550.21433.python-list@python.org> <87fv95fom0.fsf@jester.gateway.sonic.net>
X-Gmane-NNTP-Posting-Host: 197.89.15.108
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.3790.4657
X-RFC2646: Format=Flowed; Original
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4913
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.427.1426494675.21433.python-list@python.org>
Lines: 28
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1426494675 news.xs4all.nl 2933 [2001:888:2000:d::a6]:36993
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:87531


"Paul Rubin" <no.email@nospam.invalid> wrote in message 
news:87fv95fom0.fsf@jester.gateway.sonic.net...
> "Frank Millman" <frank@chagford.com> writes:
>> I like dict comprehensions, but I don't use them very often, so when I do 
>> I
>> need to look up the format.
>
> I never felt a need for them.  Do they generate better code than
>
>   d = dict((k,v) for k,v in [('name','paul'),('language','python')])  ?
>

I ran timeit, and dict comps are quite a bit quicker. This is with Python 
3.4.1 -

C:\>python -m timeit -s "x=range(65, 91); y=(chr(z) for z in x)" "dict((a, 
b) for a, b in zip(x, y))"
100000 loops, best of 3: 16.1 usec per loop

C:\>python -m timeit -s "x=range(65, 91); y=(chr(z) for z in x)" "{a: b for 
a, b in zip(x, y)}"
100000 loops, best of 3: 6.38 usec per loop

Frank