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

Guido van Rossum guido at python.org
Mon Feb 8 03🔞40 CET 2010

On Sun, Feb 7, 2010 at 12:23 PM, Brett Cannon <brett at python.org> wrote:

On Sun, Feb 7, 2010 at 10:44, Barry Warsaw <barry at python.org> wrote:

On Feb 06, 2010, at 04:39 PM, Guido van Rossum wrote:

The conflict is purely that PEP 3147 proposes the new behavior to be optional, and adds a flag (-R) and an environment variable ($PYTHONPYR) to change it. I presume Barry is proposing this out of fear that the new behavior might upset somebody; personally I think it would be better if the behavior weren't optional. At least not in new Python releases Good to know!  Yes, that's one reason why I made it option, the other being that I suspect most people don't care about the original use case (making sure pyc files from different Python versions don't conflict).  However, with a folder-per-folder approach, the side benefit of reducing directory clutter by hiding all the pyc files becomes more compelling. -- in backports such as a distribution that wants this feature might make, it may make sense to be more conservative, or at least to have a way to turn it off. For backports I think the most conservative approach is to require a flag to enable this behavior.  If we make this the default for new versions of Python (something I'd support) then tools written for Python >= 3.2 will know this is just how it's done.  I worry about existing deployed tools for Python < 2.7 and 3.1. How about this: enable it by default in 3.2 and 2.7.  No option to disable it. Allow distro back ports to define a flag or environment variable to enable it. The PEP can even be silent about how that's actually done, and a Debian implementation for Python 2.6 or 3.1 could even use the (now documented :) -X flag. Would you keep the old behavior around as well, or simply drop it? I personally vote for the latter for simplicity and performance reasons (by not having to look in so many places for bytecode), but I can see tool people who magically calculate the location of the bytecode not loving the idea (another reason why giving loaders a method to return all relevant paths is a good idea; no more guessing).

For 3.2 I think it's fine to simply drop the old behavior (as long as a good loader API is added at the same time).

But for 2.7 I think we ought to be a lot more conservative and not force tools to upgrade, so I think we should keep the old behavior in 2.7 as the default (though distros can change this if they want to, and backport if they need to).

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

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