[Tutor] conditionally defining classes

[Jeff Shannon]

Tony Cappellini wrote:

>Going off in another direction- is it Pythonic to conditionally define a
>class as in ..
>
>import sys
>OSVer= sys.getwindowsversion()[0]
>
>if OSVer == 5:
>   class OSWinXp(object):
>	def __init__(self):
>		# XP specific code goes here
>elif OSVer == 4:
>   class OsWin98(object):
>	def __init__(self):
>		# W98 specifc code goes here
>  
>

That seems acceptable to me, but I'd probably define both classes and 
then use only the appropriate one --

    class OSWinXp(object):
        # stuff

    class OSWin98(object):
        # stuff

    if OSVer == 5:
        OSWin = OSWinXp
    else:
        OSWin = OSWin98

    my_os = OSWin()

If you stuff all of the conditional stuff inside of a module, then you 
get a nice clean interface, with the client code never needing to 
know/care about the details.

    import OSWin

    my_os = OSWin.OSWin()

This is roughly how the built-in os module works...

Jeff Shannon
Technician/Programmer
Credit International