return an object of a different class

[Westley Martínez]

On Fri, 2011-02-18 at 02:25 +0000, Steven D'Aprano wrote:
> On Thu, 17 Feb 2011 15:53:14 -0800, Westley Martínez wrote:
> 
> >> > Python 3 removed longs because they were ... cryptonic!
> >> >
> >> Strictly speaking, they weren't removed. ints were removed and long was
> >> renamed int.
> > My point stands.
> 
> Your point is wrong. Ints and longs weren't unified because it is 
> "cryptonic" (cryptic?), but to avoid the user needing to care about the 
> difference between ints and longs. I've been coding in Python since 
> version 1.5, and I can tell you I hated the need to write code like this:
> 
> 
> def make_int(obj):
>     try:
>         return int(obj)
>     except ValueError:
>         return long(int)
> 
> To say nothing of:
> 
> def add(x, y):
>     try:
>         return x+y
>     except OverflowError:
>         return long(x)+long(y)
> 
> 
> Having the int class automatically promote instances to long as needed 
> was a HUGE win for simplicity and readability, while still saving memory 
> and performance for small ints.
> 
> Still not convinced that it's allowed to return objects of a different 
> type? From Python 3.1:
> 
> >>> reversed
> <class 'reversed'>
> >>> reversed((1,2,3))
> <reversed object at 0x9beb9cc>
> >>> reversed("abcd")
> <reversed object at 0x9beb9cc>
> >>> reversed([1,2,3])
> <list_reverseiterator object at 0x9beb70c>
> >>> reversed(range(10))
> <range_iterator object at 0xb7cd8a88>
> 
> 
> -- 
> Steven
But again, these types all have an identical interface.