[Python-Dev] Portable and OS-dependent module idea/proposal/brain fart

[Skip Montanaro]

I posted a note to the main list yesterday in response to Dan Connolly's
complaint that the os module isn't very portable.  I saw no followups (it's
amazing how fast a thread can die out :-), but I think it's a reasonable
idea, perhaps for Python 2.0, so I'll repeat it here to get some feedback
from people more interesting in long-term Python developments.

The basic premise is that for each platform on which Python runs there are
portable and nonportable interfaces to the underlying operating system.  The
term POSIX has some portability connotations, so let's assume that the posix
module exposes the portable subset of the OS interface.  To keep things
simple, let's also assume there are only three supported general OS
platforms: unix, nt and mac.  The proposal then is that importing the
platform's module by name will import both the portable and non-portable
interface elements.  Importing the posix module will import just that
portion of the interface that is truly portable across all platforms.  To
add new functionality to the posix interface it would have to be added to
all three platforms.  The posix module will be able to ferret out the
platform it is running on and import the correct OS-independent posix
implementation:

    import sys
    _plat = sys.platform
    del sys

    if _plat == "mac": from posixmac import *
    elif _plat == "nt": from posixnt import *
    else: from posixunix import *	# some unix variant

The platform-dependent module would simply import everything it could, e.g.:

    from posixunix import *
    from nonposixunix import *

The os module would vanish or be deprecated with its current behavior
intact.  The documentation would be modified so that the posix module
documents the portable interface and the OS-dependent module's documentation
documents the rest and just refers users to the posix module docs for the
portable stuff.

In theory, this could be done for 1.6, however as I've proposed it, the
semantics of importing the posix module would change.  Dan Connolly probably
isn't going to have a problem with that, though I suppose Guido might...  If
this idea is good enough for 1.6, perhaps we leave os and posix module
semantics alone and add a module named "portable", "portableos" or
"portableposix" or something equally arcane.

Skip Montanaro	| http://www.mojam.com/
skip@mojam.com  | http://www.musi-cal.com/~skip/
847-971-7098