General question about Python design goals

Steve Holden steve at holdenweb.com
Thu Dec 1 13:13:00 CET 2005


Antoon Pardon wrote:
> On 2005-12-01, Fredrik Lundh <fredrik at pythonware.com> wrote:
> 
>>Mike Meyer wrote:
>>
>>
>>>So why the $*@& (please excuse my Perl) does "for x in 1, 2, 3" work?
>>
>>because the syntax says so:
>>
>>    http://docs.python.org/ref/for.html
>>
>>
>>>Seriously. Why doesn't this have to be phrased as "for x in list((1,
>>>2, 3))", just like you have to write list((1, 2, 3)).count(1), etc.?
>>
>>because anything that supports [] can be iterated over.
> 
> 
> This just begs the question. If tuples are supposed to be such
> heterogenous sequences, one could indeed question why they
> support [].
> 
Presumably because it's necessary to extract the individual values 
(though os.stat results recently became addressable by attribute name as 
well as by index, and this is an indication of the originally intended 
purpose of tuples).

> And even if good arguments are given why tuples shouls support
> [], the fact that the intention of tuples and list are so
> different casts doubts on the argument that supporting []
> is enough reason to support iteration.
> 
> One could equally also argue that since iteration is at the heart
> of methods like index, find and count, that supporting iteration
> is sufficient reason to support these methods.
> 
One could even go so far as to prepare a patch to implement the required 
methods and see if it were accepted (though wibbling is a much easier 
alternative). Personally I find the collective wisdom of the Python 
developers, while not infallible, a good guide as to what's pythonistic 
and what's not. YMMV.

regards
  Steve
-- 
Steve Holden       +44 150 684 7255  +1 800 494 3119
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