Question about consistency in python language

[Steve Holden]

Kay Schluehr wrote:
> Mike Meyer wrote:
> 
> 
>>Yes, but the function "sorted" is more useful than a list method
>>"sorted" in a duck typing language.
> 
> 
> I don't see what this has to do with "duck typing"? sorted() is simply
> a generic function accepting different types. I'm not aware that
> sorted() requires a specific interface of those types it accepts.
> 
Just because you aren't aware of something doesn't stop it being true. 
The argument must be iterable, and there's a specific protocol for that.
> 
>>The function sorted works on all iterators. I can do:
>>
Ah, so you *were* aware of it.
>>
>>>>>def t(n):
>>>>>  for i in range(n):
>>>>>    yield i
>>>>>...
>>>>>print sorted(t(5))
>>
>>and have it work.
>>
>>If sorted were a method of a class - the it'd have to be implemented
>>again for every class iterable class. Either that, or you'd have to
>>create an abstract parent of all iterable classes to add it to - which
>>seems more appropriate for a B&D language than Python.
> 
> 
> Instead of extending a class hierarchy it might even be possible to
> hook a trait into the class by means of a __traits__ attribute.
> 
> http://fsl.cs.uiuc.edu/~mhills/presentations/TraitsPresentation.pdf
> 
> Generators as well as lists and tuples would provide a sortable trait.
> The sorted() function could remain available for convenience.
> 
The advantage being ... ? Perhaps you have just discovered a really 
interesting hammer, and are seeing this problem as a nail?
> 
>>And even if you do add the abstract class, how do you make my example
>>work without explictly converting the iterator to a list type?
> 
> 
> I don't know how sorted() is implemented? A naive implementation would
> in fact be nothing else then:
> 
> def sorted(iter):
>     l = list(iter)
>     l.sort()
>     return l
> 
> Kay
> 
That would indeed be a naïve implementation. The implementation is, of 
course, an implementation detail ;-) In this case it requires that 
sort() then provides all the magic - the need for magic doesn't go away!

regards
  Steve
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