[Python-Dev] file (original) (raw)

Brett Cannon brett at python.org
Fri Feb 26 23:09:26 CET 2010

On Thu, Feb 25, 2010 at 16:13, Greg Ewing <greg.ewing at canterbury.ac.nz>wrote:

Michael Foord wrote:

I thought we agreed at the language summit that if a .pyc was in the place of the source file it could be imported from - making pyc only distributions possible.

Ah, that's okay, then. Sorry about the panic! Michael is right about what as discussed at the language summit, but Barry means what he says; if you look at the PEP as it currently stands it does not support bytecode-only modules.

Barry and I discussed how to implement the PEP at PyCon after the summit and supporting bytecode-only modules quickly began to muck with the semantics and made it harder to explain (i.e. what to set file vs. compiled based on what is or is not available and how to properly define get_paths for loaders). But a benefit of no longer supporting bytecode-only modules by default is it cuts back on possible stat calls which slows down Python's startup time (a complaint I hear a lot). Performance issues become even more acute if you try to come up with even a remotely proper way to have backwards-compatible support in importlib for its ABCs w/o forcing caching on all implementors of the ABCs.

As for having a dependency on a loader, I don't see how that is obscure; it's just a dependency your package has that you handle at install-time.

And personally, I don't see what bytecode-only modules buy you. The obfuscation argument is bunk as we all know. Bytecode contains so much data that disassembling it gives you a very clear picture of what the original code was like. I think it's almost a dis-service to support bytecode-only files as it leads people who are misinformed or simply don't take the time to understand what is contained in a .pyc file into a false sense of security about their code not being easy to examine by someone else. The only perk I can see is space-saving, but that's dangerous as that ties you to a specific VM with a specific magic number (let alone that it leads to people tying themselves to CPython and ignoring the other VMs that simply do not support bytecode).

-Brett

-- Greg

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