[Python-Dev] Wordcode: new regular bytecode using 16-bit units

Victor Stinner victor.stinner at gmail.com
Wed Apr 13 18:26:00 EDT 2016

2016-04-14 0:11 GMT+02:00 Ryan Gonzalez <rymg19 at gmail.com>:
> So code that depends on iterating through bytecode via HAS_ARG is going to
> break...

Sure. This change is backward incompatible for applications parsing
bytecode in C or Python. That's why the patch also has to update the
dis module.

I don't see how you plan to keep the backwad compatibility, since the
argument size changed from 2 bytes to 1 byte. You must update your
code (written in C or Python or whatever).

Hopefully, the dis was enhanced in Python 3.4: get_instructions() now
gives nice Instructon objects rather than only pure text output.

FYI I wrote my own library to decode and decode bytecode. It provides
abstract bytecode objects to easily modify bytecode:

I suggest to use such library (or simply the dis module for simple
needs) if you have to handle bytecode, rather than writing your own

I know a few other projects which handle directly bytecode:

* https://pypi.python.org/pypi/codetransformer
* https://github.com/serprex/byteplay
* https://pypi.python.org/pypi/coverage

IHMO it's not a big deal to update these projects for the future
Python 3.6. I can even help them to support the new bytecode format.


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