Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!news.stack.nl!newsfeed.xs4all.nl!newsfeed1a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python.list@tim.thechases.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'python.': 0.02; ';-)': 0.03; 'skip:[ 20': 0.04; 'subject:Python': 0.06; 'abuse': 0.07; 'assignment': 0.07; 'dev': 0.07; 'test,': 0.07; 'subject: [': 0.09; 'subject:language': 0.09; 'times,': 0.14; '-tkc': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'stumbled': 0.16; 'language': 0.16; 'code,': 0.22; "i've": 0.25; 'said,': 0.30; 'languages': 0.32; "i'd": 0.34; 'something': 0.35; 'done': 0.36; 'doing': 0.36; 'charset:us-ascii': 0.36; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'even': 0.60; 'offer': 0.62; 'more': 0.64; 'production': 0.68; 'receive': 0.70; 'friends': 0.81; 'received:50.22': 0.84; 'subject:NOT': 0.84; 'ugly,': 0.84
Date: Thu, 27 Mar 2014 11:08:56 -0500
From: Tim Chase <python.list@tim.thechases.com>
To: python-list@python.org
Subject: Python language hack for C-style programmers [DO NOT USE!] :-)
X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; x86_64-pc-linux-gnu)
Importance: low
X-Priority: 4 (Low)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - boston.accountservergroup.com
X-AntiAbuse: Original Domain - python.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - tim.thechases.com
X-Get-Message-Sender-Via: boston.accountservergroup.com: authenticated_id: tim@thechases.com
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
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.8622.1395936527.18130.python-list@python.org>
Lines: 35
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1395936527 news.xs4all.nl 2850 [2001:888:2000:d::a6]:51586
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:69202

Multiple times, I've seen someone want something like what C-style
languages offer where assignment is done in a test, something like

  if (m = re.match(some_string)):
    do_something(m)

So when I stumbled upon this horrific atrocity of language abuse and
scope leakage, I thought I'd share it.

  if [m for m in [regex.match(some_string)] if m]:
    do_something(m)

And presto, assignment in an if-statement.  It even "works" in
while-statements too:

  while [m for m in [regex.match(some_string)] if m]:
    some_string = do_something(m)

That said, it's ugly, far more opaque/inefficient than the traditional

  m = regex.match(some_string)
  if m:
    do_something(m)

and if I ever caught someone on my dev teams doing this in production
code, their backside would receive a stern conversation with my
footwear.

Friends don't let friends program C in Python. ;-)

-tkc