PEP 276 (was Re: Status of PEP's?)

[James_Althoff at i2.com]

[Carel Fellinger]
> and define your classes to let __len__ return an Int object.
>
>     class List(list):
>         def __len__(self):
>             return Int(len(list(self)))
>
> trying it out, yack it doesn't work, len forces it into an int again:(
>
>     >>> spam = List("spam")
>     >>> type(spam.__len__())
>     <class '__main__.Int'>
>     >>> type(len(spam))
>     <type 'int'>
>
> I think this qualifies as a bug.


Here's a similar way to try out PEP 276.

Python 2.2 (#28, Dec 21 2001, 12:21:22) [MSC 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> from __future__ import generators
>>>
>>> class iint(int):
...   def __iter__(self):
...     i = 0
...     while i < self:
...       yield i
...       i += 1
...     raise StopIteration
...
>>> __len = len
>>>
>>> def len(seq):
...     return iint(__len(seq))
...
>>> l = ['a','b','c','d','e','f','g','h']
>>>
>>> for i in len(l):
...   if i % 2 == 0:
...     print l[i]
...
a
c
e
g
>>> # PEP 276 in action <wink>
...
>>>


BTW, if anyone knows how to add a method to class int (without resorting to
the C code), let me know.  I can't seem to get around int.__dict__ being a
dict-proxy that can't be subclassed, modified, etc.  Probably by design
<0.1 wink>.

Jim