[Python-Dev] integer subclass range behavior

[Joseph Armbruster]

All,

I posted this up to comp.lang.python earlier today and asked a few questions 
around IRC.  The general consensus appeared to be that this was a bug.  Before 
opening up an issue on it, I wanted to run it by this list first (just in case) 
  Here is a copy / paste from comp.lang.python:

URL:

http://groups.google.com/group/comp.lang.python/browse_frm/thread/801f227fceff4066#e0305608a5931af1

Post:

I was wondering what would happen, so I tried this out for the heck of it with:
Python 3.0a2 (py3k:59572M, Dec 19 2007, 15:54:07) [MSC v.1500 32 bit (Intel)] 
on win32

class a(int):
   def __new__(cls,number):
     return int.__new__(cls,number)

for x in range(0,a(5)):
   print(x)

Which resulted in a:

Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "a.py", line 5, in <module>
     for x in range(0,a(5)):
SystemError: ..\Objects\longobject.c:400: bad argument to internal
function
[41030 refs]

It looks like the rangeobject performs a FitsInLong test on each of
the parameters to range, which uses the function
_PyLong_FitsInLong(PyObject *vv) within longobject.c.  In tern, this
performs a typecheck:  #define PyLong_CheckExact(op) (Py_TYPE(op) ==
&PyLong_Type) that fails.

Interesting!