[Python-Dev] PEP 3147: PYC Repository Directories

[Guido van Rossum]

On Sat, Feb 6, 2010 at 5:10 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Ben Finney wrote:
>> Right; I don't see who would disagree with that. I don't see any
>> conflict between “decouple compiled bytecode file locations from source
>> file locations” versus “predictable location for the compiled bytecode
>> files”.
>
> The more decoupled they are, the harder it is to manually find the
> bytecode file.
>
> With the current .pyc scheme, .pyr folders or an SVN style Python cache
> directory, finding the bytecode file is pretty easy, since the cached
> file is either in the same directory as the source file or in a
> subdirectory.
>
> With any form of shadow hierarchy though, it gets trickier because you
> have to:
> 1. Find the root of the shadow hierarchy
> 2. Navigate within the shadow hierarchy down to the point that matches
> where your source file was
>
> It's a fairly significant increase in mental overhead. It gets much
> worse if the location of the shadow hierarchy root is configurable in
> any way (e.g. based on sys.path contents or an environment variable).
>
> Restricting the caching mechanism to the folder containing the source
> file keeps things a lot simpler.

Great way of explaining why the basic folder-per-folder model wins
over the folder-per-sys.path-entry model! The basic folder-per-folder
model doesn't need to know what sys.path is. (And I hadn't followed
previous messages in the thread with enough care to understand the
subtlen implications of Ben's point. Sorry!)

-- 
--Guido van Rossum (python.org/~guido)