Message-ID:

The universe seems neither benign nor hostile, merely indifferent. -- Sagan

devel / comp.lang.python / RE: New assignmens ...

RE: New assignmens ...

<mailman.146.1635551032.23718.python-list@python.org>

https://www.rocksolidbbs.com/devel/article-flat.php?id=20278&group=comp.lang.python#20278

copy link Newsgroups: comp.lang.python

Path: i2pn2.org!i2pn.org!news.swapon.de!fu-berlin.de!uni-berlin.de!not-for-mail
From: avigross@verizon.net (Avi Gross)
Newsgroups: comp.lang.python
Subject: RE: New assignmens ...
Date: Fri, 29 Oct 2021 19:43:47 -0400
Lines: 101
Message-ID: <mailman.146.1635551032.23718.python-list@python.org>
References: <MN2PR02MB68461EB83EC01991C31D6752A8839@MN2PR02MB6846.namprd02.prod.outlook.com>
<00a701d7c9e9$0d745650$285d02f0$@verizon.net>
<CAPTjJmpfVz_TjRnpOhmO33eqYqxXitO0FGqnoHr=RvPHV+jm2Q@mail.gmail.com>
<f83e5665-5262-28d2-efc9-6c704e1e1f35@DancesWithMice.info>
<CAPTjJmr-_jPLRwATvMY+8SeHOwP=EfAcjKqZ96+ezGJk_cDOog@mail.gmail.com>
<7fe4dae1-0144-8e99-cc32-17d733961df1@vub.be>
<034401d7cb5f$5b5619e0$12024da0$@verizon.net>
<83918585-0e37-f785-43d8-2a26350c3695@vub.be>
<004a01d7cc22$4c055050$e40ff0f0$@verizon.net>
<ec690126-b073-a14b-cb8f-43af01ec619a@vub.be>
<024201d7cd1e$d1be1f90$753a5eb0$@verizon.net>
Mime-Version: 1.0
Content-Type: text/plain;
charset="utf-8"
Content-Transfer-Encoding: quoted-printable
X-Trace: news.uni-berlin.de agdmiq4AwZGCrYcM/JgNwwfJHK+SDUlq8npFGQ3CGEOA==
Return-Path: <avigross@verizon.net>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
Authentication-Results: mail.python.org; dkim=pass
reason="2048-bit key; unprotected key"
header.d=verizon.net header.i=@verizon.net header.b=BIyU7HjF;
dkim-adsp=pass; dkim-atps=neutral
X-Spam-Status: OK 0.004
X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'this:': 0.03; 'def': 0.04;
'variable': 0.05; 'lets': 0.07; 'string': 0.07; 'suggestion':
0.07; 'bot': 0.09; 'meant': 0.09; 'neat': 0.09; 'question:': 0.09;
'readable': 0.09; 'trivial': 0.09; 'url:mailman': 0.15; 'antoon':
0.16; 'assuming': 0.16; 'avi': 0.16; 'computation.': 0.16;
'gross': 0.16; 'indeed': 0.16; 'instead.': 0.16; 'pardon': 0.16;
'pardon.': 0.16; 'properly.': 0.16; 'received:(vzm hermes smtp
server)': 0.16; 'reference,': 0.16; 'schreef': 0.16; 'things,':
0.16; 'tries': 0.16; 'python': 0.16; 'october': 0.17; 'values':
0.17; 'figure': 0.19; 'to:addr:python-list': 0.20; 'language':
0.21; 'languages': 0.22; 'code': 0.23; 'lines': 0.23; 'run': 0.23;
'skip:- 10': 0.25; 'url-ip:188.166.95.178/32': 0.25; 'url-
ip:188.166.95/24': 0.25; 'python,': 0.25; 'extension': 0.25;
'url:listinfo': 0.25; 'url-ip:188.166/16': 0.25; 'again,': 0.26;
'friday,': 0.26; 'object': 0.26; 'creating': 0.27; 'function':
0.27; 'purpose': 0.28; 'attempt': 0.31; 'url-ip:188/8': 0.31;
'think': 0.32; 'python-list': 0.32; 'but': 0.32; 'there': 0.33;
'someone': 0.34; 'mean': 0.34; 'header:In-Reply-To:1': 0.34;
'question.': 0.35; 'request': 0.35; 'functions': 0.36; 'work,':
0.36; 'people': 0.36; 'change': 0.36; 'necessarily': 0.37;
'currently': 0.37; 'using': 0.37; 'way': 0.38; 'adding': 0.39;
'setting': 0.39; 'something': 0.40; 'try': 0.40; 'should': 0.40;
'family': 0.60; 'including': 0.60; 'above': 0.62; 'from:': 0.62;
'to:': 0.62; 'showing': 0.62; 'security': 0.64; 'down': 0.64;
'imagine': 0.64; 're:': 0.64; 'won\xe2\x80\x99t': 0.64; 'your':
0.64; 'well': 0.65; 'choose': 0.67; 'exactly': 0.68; 'within':
0.69; 'front': 0.70; '2021': 0.71; 'interesting': 0.71;
'challenges': 0.76; 'implemented': 0.76; 'sent:': 0.78;
'returned': 0.81; 'var': 0.81; 'extra': 0.84; 'reasons': 0.84;
'method,': 0.84; 'that:': 0.91; 'aspects': 0.93
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=verizon.net; s=a2048;
t=1635551029; bh=cWvzUKcRUNBSJf5ADksulcFrxagl5DG5lfJfnxjC4bo=;
h=From:To:References:In-Reply-To:Subject:Date:From:Subject:Reply-To;
b=BIyU7HjF7M3L89CELHYyGJwgrIsD3n1MZq1PNBuUZwAqs0P3SGRk25bCCoNWDLo4+/OZ/UTWIVg5dNZRsYf5kB5GsMoj0qdzPwvYZZhzd8D/kOqCY7MDf+jpb5qWNIu2fttc4vi7iS10HRfghz5Lvxd/B7Z8FGC4mke2ut1GLTfHzIlkMG9xUOdsXhUHITv1S4NNPgrqJ8ywAr4Ew8VvLaubyU9INoB7oCOWCSofYX++lvsCoHGP6DIDWAPTYxAXNrjWwr3cSRiH8OBrxPgNaoN9fqPDZ5YFGpVdjQqCTJhcttpGGmptev2dHSS5MhAskpf64vlNYMEL8jYKTIP+iw==
X-SONIC-DKIM-SIGN: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048;
t=1635551029; bh=E5QhH1tj4ztUb3jK1PGF+8Px+cXZRKSoS/iUJugBU3I=;
h=X-Sonic-MF:From:To:Subject:Date:From:Subject;
b=McyA6S9jgw4069+CTrOuaxaz1SgYF/gPCLfiRvlUxkWe+0glvnCxpCTdgPIlc3fai04w6m/z0KP+PxQSQiIG1rfY+zicGz+dEfvmRihkSKbaB2EdZlUcqtfmOxNFaXNBuOoMNXd2ett5IZWvK2HAOlb17TEDw3s4PX9llhfW2SyjG9opNG4b+g4usq/FHO6I9K8AqKteieLP23sziOJ/w9mwnprlT0YEUMqIrGCZGogw6w3RN9wL+HO3eiho4yjmk2FZ3BFBTWZ9Jae9fxxzdYUklvdVyXih7Akaj4nt3PTARvd6OlgtekIU/HNudWZwZGmaIiyilMSbYdYwgmGYzg==
X-YMail-OSG: ReYgdycVM1lvp_mVjMvsWItiLl4YCZvW_SwebcMGg.JiS45gawymz55ul.00gHc
MdpLGyISohQ1j_ZWZgdq5LT1VZlu45R43GQA4AEvNlIP2ruUXdg4TKhrQnNhNoR.AuRT5v5kRIuH
xsdQmmRHgOLyWwONQt0juMrZkT5Hrd6VnzmTETpD1WVBhOwglfcuw7B7m1JOhTskHo11d6haYHp2
Dty2R8CGMd_rB4hXaXOe1HyhqSMpxEnaLrhtrOTJ40.g0fIBHCkxAI2fWxrEIdilY1rucv_ZB_Pd
1BKPG1cl.E8bI0dQO4ARl7pa_tulgCa3l2KdjIVAqwcIxkTvI804lyNYvm8FC1ZSovQLi16F.Fi1
FR3m93d9wVX4xX_RM3J.UzmNfNNJMCLeypj1kwg_o8noe6B_qxGhpLoJX1NHHLIf7lCspR9FJFhc
K_zIAsV6GqHnO1tnVarehfb4ApScgdjuXB0xzUMeHErc.1aTyQzfznR70fs11PIbCCeIPPJBr57m
dov3NwQV1oU75Doh4caHKEDqQdeNPTxDi1FrmoFX3cQ4LuZOH7AigDdHxVtguhnP.A8FYSny.LY5
k9gfXQ2KvwPFaIp1dcUbJchZxr_uSIPvHrdzfXgAi4k1KYFpNLpjCsnHydrc7sc2rOL2T7sYhV0a
NAJx7Idsz5_bMKRCaIWqBvA31hDoe8e68bsh4BFesBuUWGla2drICEc974PhfdR1VDWKnRnGx4x3
h1PpkAPaAHYrQ3UX4TH9D4SEiiPgvgWkK91vaXDlLzC17GHgS0jn6nqPOpZn9cIcCttr4sF3wuH3
NF.c9fiONjcwiOYTkn4bBXl1DG3Q6VOonnmPql1GnK0jsICv2yDex_CroAuy7W41YaJXabIujF2W
9feryMkfPLaZ5atM1uRjHfo.bEADQIs9wuKOMvP5iePJFvdhoSKkSzbtpWHxNLW_y8y7v.6sW3Si
jzXenCdH43tB9Lt5gSQ74WaU6JPu3nEPpPe9XmaJs3hMKhEcKDNlBs2yNENRM36Rp74aKv.TWRzw
wHQu5dZ36fp59NV7U37WMbxu3.pwXs9KLDbk4iJfJOURYYy3G7GxUIQNjKpnTGjSh1kiUoyZn2Ff
QIAUZmc4J0WfNk2lTtZsJcgHGjSQbGd39MXcd81JT_FpQ7vCOvu87QqNnNXX6mqvlfXOgdRsnjHk
ScSSwdguq.ygP1iN_zORqowOATTYX9.09xpb3G85VbL3rkBKtJwVs0mJxreZHSLFOUZAA3rM7Ok1
6PPhxTjngkAG9QueGNge0PGzSnztBES1u2ZjHLRUpBvYLnEZAc9xQ.MRX7AotzZx4v5BzOIXTgr2
G987DkE8edL.F3vhOIdO7f2Xzt7N5HAa1NTu6OwcPOTiz9xoB3TMhpTvK.Yn132VkUhHuMisiSXJ
iF7YX4coe3DWs5nF2IGnc2QHl9S98lszS9LfD5AiRowU11dFlPWAAE0W9r8ydxm9zsLiZUooJ1to
ISBT9Xh81M2j_mi3lw4Oi2l2E1WuH0vLcNEbNh83izyGskLoqWnNSkMP1YfrL1_xjOKzvQy05SRH
PnOG_eNcsZtBq82BP4XZnCHsihXkz76go5JkND9KvUZuuiiCVn1pfaYIZsWwugwFoD_oIF.5uSgM
RnnoEIrntYhJ_I094TbkeDF.0wCBuPCedC3T.H2NwwMcS57BRlUfJ_W8OJp2OKbpOl3_IXoTciU.
dqSypktagcGGfftzydIsC0sHffFfuAM9ZCVjd5uFJbfjGokSXOLPQ3PJX4Vl2UQExTyyagA8ei.k
8Lw.KmmEHG.8rGmw95ht1HeQEd3rkKdVRqThuRmKzmLnhEcANHQDtjVBq6b0LMl5KWGBQSV.xlbA
eiCJiVg4Gk0AeHXpwwP7V4yKZ0_YyyuOWIZnyUGEpN4Yu9wMplDDhxalbduvXWYzQ.UIW2_ILyfG
tbM5YsMv1dsShhsw6bOVsmVAfz2Vx8QT5pe05Fj51Ki5U5kKMYleFwLh_.2VaA7wfQ6bQakCXRxf
k8lyo9jBtS_rVsf6fMjl0h9Lw6tVLJ8Ijqnss95jpOtLBEysAOixEcuHqUK_R7wFfB4mgcw5dd_G
04Qolf2XUdvzQiqwf4baMZYQeUFKLfmTCKXTMZFfbmCdVrcmVhLbwbWOQFg3fbagAWzfx2y87i3g
m5XZN4nAc0iE3hMNg0wKTgpPpH5neRdUXU0Q8
X-Sonic-MF: <avigross@verizon.net>
In-Reply-To: <ec690126-b073-a14b-cb8f-43af01ec619a@vub.be>
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AQIabq3W4q9bEf96n0X0U3+MV//5CwFhWOenAxR6e+ECJA4zFALUI9ekAcRwKU4DEoQnEwE6LatjAmC3E4MBxn8Ay6rIKZFQ
Content-Language: en-us
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.35
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: <https://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>
X-Mailman-Original-Message-ID: <024201d7cd1e$d1be1f90$753a5eb0$@verizon.net>
X-Mailman-Original-References: <MN2PR02MB68461EB83EC01991C31D6752A8839@MN2PR02MB6846.namprd02.prod.outlook.com>
<00a701d7c9e9$0d745650$285d02f0$@verizon.net>
<CAPTjJmpfVz_TjRnpOhmO33eqYqxXitO0FGqnoHr=RvPHV+jm2Q@mail.gmail.com>
<f83e5665-5262-28d2-efc9-6c704e1e1f35@DancesWithMice.info>
<CAPTjJmr-_jPLRwATvMY+8SeHOwP=EfAcjKqZ96+ezGJk_cDOog@mail.gmail.com>
<7fe4dae1-0144-8e99-cc32-17d733961df1@vub.be>
<034401d7cb5f$5b5619e0$12024da0$@verizon.net>
<83918585-0e37-f785-43d8-2a26350c3695@vub.be>
<004a01d7cc22$4c055050$e40ff0f0$@verizon.net>
<ec690126-b073-a14b-cb8f-43af01ec619a@vub.be>

by: Avi Gross - Fri, 29 Oct 2021 23:43 UTC

Antoon,

As long as we understand that my suggestion is not meant to be taken seriously, your extension is along the lines I intended.

You might indeed have a family of helper functions whose purpose is to bot make a change on the side and return the value to be used in a computation. Your specific implementation of something like that:

def setxattr(obj, attr, value):
setattr(obj, attr, value)
return value

Would need to have access to the original object and change it in a way that propagates properly. So when you do this:

if setxattr(self, 'ctr', self.ctr - 1) <= 0 :

Then assuming passing it 'ctr' as a string makes sense, and the object self is passed by reference, I can see it working without a walrus operator.

But it is extra overhead. This being python, setting values WITHIN an object is a challenge. I mean there are ways to make a value readable but not writeable or writeable only using a designated method, or an attempt to set the value may be intercepted and the interceptor may choose to do something different such as ignoring the request if someone tries to set the time to thirteen o'clock or even setting it to 1 o'clock instead. The above kind of code perhaps should not return value but obj.attr so we see what was stored. But again, Python lets you intercept things in interesting ways so I can imagine it showing something other that what you stored.

Sigh

As noted, the general case implemented walrus style may have challenges and even efforts like the above may not always be straightforward.

Language design is not as trivial as some think and like with many things, adding a neat new feature may open up holes including security holes if people figure out how to abuse it. Shutting down some such abilities is exactly why people code defensively and try to hide the inner aspects of an object by doing things like having a proxy in front of it and creating getters and setters.

-----Original Message-----
From: Python-list <python-list-bounces+avigross=verizon.net@python.org> On Behalf Of Antoon Pardon
Sent: Friday, October 29, 2021 10:04 AM
To: python-list@python.org
Subject: Re: New assignmens ...

Op 28/10/2021 om 19:36 schreef Avi Gross via Python-list:
> Now for a dumb question. Many languages allow a form of setting a variable to a value like:
>
>
>
> assign(var, 5+sin(x))
>
>
>
> If we had a function that then returned var or the value of var, cleanly, then would that allow an end run on the walrus operator?
>
>
>
> if (assign(sign, 5+sin(x)) <= assign(cosign, 5+cos(x))) …
>
>
>
> Not necessarily pretty and I am sure there may well be reasons it won’t work, but I wonder if it will work in more places than the currently minimal walrus operator.

This was the orginal code to illustrate the question:

if (self.ctr:=self.ctr-1)<=0

So if I understand your sugested solution it would be something like:

def setxattr(obj, attr, value):
setattr(obj, attr, value)
return value

if setxattr(self, 'ctr', self.ctr - 1) <= 0

Did I get that right?

--
Antoon Pardon.

--
https://mail.python.org/mailman/listinfo/python-list