Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!news-peer.in.tum.de!news.belwue.de!news.osn.de!diablo2.news.osn.de!news.tele.dk!news.tele.dk!small.news.tele.dk!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <bsk16@case.edu>
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; 'raises': 0.07; 'args,': 0.09; 'bug?': 0.09; 'raised.': 0.09; 'tuple': 0.09; 'valueerror:': 0.09; 'subject:error': 0.09; '"...': 0.16; '"expected': 0.16; '14",': 0.16; 'a,b,c': 0.16; 'benjamin': 0.16; 'iterable,': 0.16; 'rhs': 0.16; 'roy': 0.16; 'unpack': 0.16; 'unpacking': 0.16; 'wrote:': 0.18; '>>>': 0.18; 'this?': 0.19; '(most': 0.21; 'so.': 0.22; 'dec': 0.22; "doesn't": 0.22; 'header:In-Reply-To:1': 0.22; 'items.': 0.23; 'traceback': 0.24; 'function': 0.27; 'variable': 0.28; 'lists': 0.28; 'message-id:@mail.gmail.com': 0.28; 'pm,': 0.29; 'values': 0.32; 'returning': 0.32; 'thu,': 0.32; 'instead': 0.33; 'to:addr:python-list': 0.34; 'probably': 0.34; 'too': 0.34; 'things': 0.34; 'last):': 0.34; 'supposed': 0.35; 'file': 0.36; 'but': 0.37; 'list,': 0.37; 'received:google.com': 0.37; 'could': 0.37; 'received:209.85': 0.38; "it's": 0.40; 'received:209': 0.40; 'to:addr:python.org': 0.40; 'more': 0.61; '2011': 0.61; 'stop': 0.63; 'subject:day': 0.68; '\xa0there': 0.91
MIME-Version: 1.0
In-Reply-To: <4EE10B63.2010600@stoneleaf.us>
References: <roy-9DEDD9.09233308122011@news.panix.com> <jbqil6$esn$1@dough.gmane.org> <mailman.3417.1323357938.27778.python-list@python.org> <18647617.2258.1323358966076.JavaMail.geo-discussion-forums@yqf20> <mailman.3421.1323359453.27778.python-list@python.org> <3164448.1087.1323369765528.JavaMail.geo-discussion-forums@yqcm37> <CAMuTYXhG-+CVm1BC5TKr2ektgPN1KC2BnbLXMy+X_Z-GrWMotg@mail.gmail.com> <4EE10B63.2010600@stoneleaf.us>
Date: Thu, 8 Dec 2011 14:38:28 -0500
Subject: Re: Misleading error message of the day
From: Benjamin Kaplan <benjamin.kaplan@case.edu>
To: python-list@python.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Junkmail-Whitelist: YES (by domain whitelist at mpv1.tis.cwru.edu)
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://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: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.3445.1323373172.27778.python-list@python.org>
Lines: 50
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1323373172 news.xs4all.nl 6840 [2001:888:2000:d::a6]:37835
X-Complaints-To: abuse@xs4all.nl
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:16864

On Thu, Dec 8, 2011 at 2:09 PM, Ethan Furman <ethan@stoneleaf.us> wrote:
> Benjamin Kaplan wrote:
>>
>> On Thu, Dec 8, 2011 at 1:42 PM, Roy Smith <roy@panix.com> wrote:
>>>
>>> (some,
>>> =A0very,
>>> =A0long,
>>> =A0list,
>>> =A0of,
>>> =A0variable,
>>> =A0names,
>>> =A0to,
>>> =A0get,
>>> =A0the,
>>> =A0stuff,
>>> =A0unpacked,
>>> =A0into) =3D function_that_should_return_a_14_tuple()
>>>
>>> raises
>>>
>>> ValueError: too many values to unpack
>>>
>>> Quick, what's the bug? =A0Did I forget a variable on the LHS, or is my
>>> function returning more things than it should? =A0I know it's supposed =
to be
>>> 14, but I don't know which side is wrong. =A0Had it said "... expected =
13, got
>>> 14", I would know immediately.
>>>
>>
>> If the RHS was a tuple or a list, yes you could know immediately. But
>> unpacking works with any iterable, so it probably doesn't special-case
>> lists and tuples. Iterables don't have a size- they just keep going
>> until StopIteration is raised. So in EVERY SINGLE CASE, you would get
>> "expected n args, got n+1" even if the iterable would return 24 items
>> instead of 14, or would never stop returning items.
>
>
> Not so. =A0There could be fewer, in which you could see "expected 13 args=
, got
> 7."
>

You mean like this?

>>> a,b,c =3D ['a','b']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 2 values to unpack