The attached files reproduce a wierd problem where by
the builtin file() function completely vanishes from
python.
Notice that __builtin__ changes type from module to dict.

In the attached tar files find:
   manufacture    - main program
   bob.py            - module
   a.a                 - file to open

Untar and run:

python manufacture

Notice that file()is no ware to be found in side of bob.py

This runs the same on all 2.3 and 2.4 on Windows, Linux
and Mac OS X.

Logged In: YES 
user_id=31435

No, __builtins__ (note the trailing 's') changes type from 
module to module, not __builtin__.  __builtins__ is an 
implementation detail, and you shouldn't use it at all.  
__builtin__ (no trailing 's') is a built-in module, and you're free 
to use that, but then you have to import it explicitly:

import __builtin__
__builtin__.file

There's more in the Language (not Library) reference manual, 
in the section "Naming and Binding".

Logged In: YES 
user_id=21627

As Tim says, __builtins__ is a dictionary sometimes.
Therefore, it is no surprise that __builtins__.file does not
exist - dictionaries don't have a file attribute. As this is
apparently what you meant when you said that file()
"vanishes", I'm closing the report as invalid.