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From: Devin Jeanpierre <jeanpierreda@gmail.com>
Date: Thu, 2 Feb 2012 01:34:48 -0500
Subject: Re: copy on write
To: "John O'Hagan" <research@johnohagan.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:19769

On Wed, Feb 1, 2012 at 10:18 PM, John O'Hagan <research@johnohagan.com> wro=
te:
> On Fri, 13 Jan 2012 10:40:47 -0800
> Ethan Furman <ethan@stoneleaf.us> wrote:
>
>> Steven D'Aprano wrote:
>> > Normally this is harmless, but there is one interesting little
>> > glitch you can get:
>> >
>> >>>> t =3D ('a', [23])
>> >>>> t[1] +=3D [42]
>> > Traceback (most recent call last):
>> > =C2=A0 File "<stdin>", line 1, in <module>
>> > TypeError: 'tuple' object does not support item assignment
>> >>>> t
>> > ('a', [23, 42])
>
> IMHO, this is worthy of bug-hood: shouldn't we be able to conclude from t=
he TypeError that the assignment failed?

It did fail. The mutation did not.

I can't think of any way out of this misleadingness, although if you
can that would be pretty awesome.

-- Devin