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From: Mark Lawrence <breamoreboy@yahoo.co.uk>
Subject: Re: Default Value
Date: Sat, 22 Jun 2013 09:26:12 +0100
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Xref: csiph.com comp.lang.python:48919

On 22/06/2013 02:31, Steven D'Aprano wrote:
> On Sat, 22 Jun 2013 05:07:59 +1000, Chris Angelico wrote:
>
>> Oh! I know. Function argument defaults will now be restricted to
>> int/float/tuple. That would do it, right? Nobody would be bothered by
>> little restrictions like that, would they.
>
> Alas, tuples won't do it. Fortunately, you can include str and bytes
> (unicode and str) and frozenset in the "Good List". Tuples have to go
> into the "Bad List" because, although they themselves are immutable,
> their contents may not be. Imagine the confusion and horror that poor
> developers will experience when they do something like this:
>
> def func(arg, extra=(23, 'foo', [])):
>      [code goes here...]
>      extra[2].append("something")
>      [more code...]
>
>
> and they've now mutated the immutable default!
>
> Thinking about this, I think that the only safe thing to do in Rickython
> 4000 is to prohibit putting mutable objects inside tuples. Putting a list
> or a dict inside a tuple is just a bug waiting to happen!
>

How about naming the fork RickedPython 4000, where ricked is defined 
here http://www.urbandictionary.com/define.php?term=ricked ?

-- 
"Steve is going for the pink ball - and for those of you who are 
watching in black and white, the pink is next to the green." Snooker 
commentator 'Whispering' Ted Lowe.

Mark Lawrence