on Windows, the stat() function always returns True for some special
device names (nul, con, com1, lpt1...), even when followed by an extension.

Thus "import con" manages to find that "con.py" exists, and tries to
read from it... fun.

A solution is to use GetFileAttributes() instead.

Note that on python2.5.2, the error message suggest that we have such a
problem, but fortunately the error is still an ImportError::
  >>> import nul
  ImportError: DLL load failed: Le module spécifié est introuvable.

The title is misleading -- if what you show is correct then "import nul"
doesn't succeed :)

Sorry, I was not clear.
With python 2.5.2, "import nul" correctly raises ImportError, even if
the error message is slightly misleading.

With a recent release25-maint (and all other branches), "import nul"
does succeed, and creates an empty module. 
"import con" seems to block, it actually waits for the user to enter
text and type ^Z. Then it prints to the console some bizarre text that
looks like the content of a .pyc file:

Python 2.5.3a0 (release25-maint, Jun 11 2008, 13:17:36) [MSC v.1200 32
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import con
^Z
a=1
b=2
c=3
^Z
│≥
    c        ☺   @   s►   d  Z  d☺ Z☺ d☻ S(♥   i☻   i♥   N(☻   t☺   bt☺
  c(    (    (    s♠   con.py   <module>☺   s☻   ♠☺    [27520 refs]
>>> dir(con)
['__builtins__', '__doc__', '__file__', '__name__', 'b', 'c']
[27533 refs]

I was wrong. It seems that an installed python works correctly, but a
python running from its build directory has the problem.

OK, I think I got is now. The difference is between debug and release
builds.

Explanation:
- in release build, "import nul" calls stat("nul.pyd") which succeeds.
It then tries LoadLibrary("nul.pyd"), which fails with a DLL error.
- in debug builds, "import nul" first tries stat("nul_d.pyd") which
fails. It then tries stat("nul.py"), which succeeds to return an empty file!

Whaaaa.

GetFileAttributes() succeeds for "nul", but GetFileAttributesEx() fails.
Maybe is it good idea to use GetFileAttributesEx()?

# test code

import ctypes
import ctypes.wintypes as type

dll = ctypes.windll.kernel32

print dll.GetFileAttributesA("nul") # 32

class WIN32_FILE_ATTRIBUTE_DATA(ctypes.Structure):
	_fields_ = [("dwFileAttributes", type.DWORD),
	            ("ftCreationTime", type.FILETIME),
	            ("ftLastAccessTime", type.FILETIME),
	            ("ftLastWriteTime", type.FILETIME),
	            ("nFileSizeHigh", type.DWORD),
	            ("nFileSizeLow", type.DWORD)]

GetFileExInfoStandard = 0

wfad = WIN32_FILE_ATTRIBUTE_DATA()

print dll.GetFileAttributesExA("nul", GetFileExInfoStandard,
ctypes.byref(wfad)) # 0

Since I don't have access to Windows I am unassigning. Amaury, if this
is still a problem should we go ahead and switch to
GetFileAttributesEx()? Or just realize this is a problem for people
developing Python?

It's a problem with debug builds on Windows.
Lowering priority. 

Also, it is likely that the new import library will correct the problem.