[Python-Dev] PEP 3147: PYC Repository Directories (original) (raw)

Guido van Rossum guido at python.org
Sun Feb 7 02:32:15 CET 2010

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)

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