[Web-SIG] Standardising containment.

[Phillip J. Eby]

At 01:46 PM 9/6/04 +0100, Alan Kennedy wrote:
>[Alan Kennedy]
> >>1. Temporary storage/scratch directory.
>
>On thinking further about the temp directory issue, I see now that it is 
>but one example of a class of problems relating to accessing physical 
>resources on the local machine.
>
>The other main one that springs to mind is how WSGI applications discover 
>the file-system path name that corresponds to an URI.

*boggle*  Why do you think that URIs have anything to do with file 
paths?  In the general case, they are entirely unrelated.


>[snip]
>Therefore I propose that WSGI somehow attempt to standardise access to 
>local resources on the disk. This could be done, perhaps, by providing a 
>function which resolves a logical URI to a physical resource. J2EE has 
>just such a function (surprise ;-), called ServletContext.getRealPath(), 
>which returns a file-system path name which is relative to the 
>CONTEXT_PATH mentioned above.
>
>Without WSGI providing such local mapping functions, I don't see how WSGI 
>applications/middleware can map URIs to files, without undertaking 
>platform specific tricks.

Well-written Python applications make this sort of thing part of their 
configuration today already, because in the general case (e.g. mod_rewrite) 
this stuff just plain isn't guessable.

Also, if you need access to local resources, relative to some Python 
module, just grab the '__file__' attribute/variable of that module, and 
then use 'os.path' functions to portably manipulate it.  E.g.:

     my_dir = os.path.dirname(__file__)
     target = os.path.join(os.path.join(my_dir,"images"),"stars.jpg")

This is simple and portable.  If you need something more complex, you 
should probably have configuration specific to the application that spells 
out what it needs to know.