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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Fri, 21 Jun 2013 19:27:42 -0600
Subject: Re: Default Value
To: Python <python-list@python.org>
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Xref: csiph.com comp.lang.python:48897

On Fri, Jun 21, 2013 at 7:15 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> On Fri, 21 Jun 2013 23:49:51 +0100, MRAB wrote:
>
>> On 21/06/2013 21:44, Rick Johnson wrote:
> [...]
>>> Which in Python would be the "MutableArgumentWarning".
>>>
>>> *school-bell*
>>>
>> I notice that you've omitted any mention of how you'd know that the
>> argument was mutable.
>
> That's easy. Just call ismutable(arg). The implementation of ismutable is
> just an implementation detail, somebody else can work that out. A
> language designer of the sheer genius of Rick can hardly be expected to
> worry himself about such trivial details.

While we're at it, I would like to petition for a function
terminates(f, args) that I can use to determine whether a function
will terminate before I actually call it.