PEP 3147 - new .pyc format

Mensanator mensanator at
Sat Jan 30 23:36:52 CET 2010

On Jan 30, 4:14 pm, John Roth <johnro... at> wrote:
> PEP 3147 has just been posted, proposing that, beginning in release
> 3.2 (and possibly 2.7) compiled .pyc and .pyo files be placed in a
> directory with a .pyr extension. The reason is so that compiled
> versions of a program can coexist, which isn't possible now.
> Frankly, I think this is a really good idea, although I've got a few
> comments.
> 1. Apple's MAC OS X should be mentioned, since 10.5 (and presumably
> 10.6) ship with both Python release 2.3 and 2.5 installed.

Mac OSX 10.6 has 2.6 installed.

> 2. I think the proposed logic is too complex. If this is installed in
> 3.2, then that release should simply store its .pyc file in the .pyr
> directory, without the need for either a command line switch or an
> environment variable (both are mentioned in the PEP.)
> 3. Tool support. There are tools that look for the .pyc files; these
> need to be upgraded somehow. The ones that ship with Python should, of
> course, be fixed with the PEP, but there are others.
> 4. I'm in favor of putting the source in the .pyr directory as well,
> but that's got a couple more issues. One is tool support, which is
> likely to be worse for source, and the other is some kind of algorithm
> for identifying which source goes with which object.
> Summary: I like it, but I think it needs a bit more work.
> John Roth

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