[Python-ideas] Incorporating something like byteplay into the stdlib

[Andrew Barnert]

On Feb 12, 2016, at 12:36, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
> 
>> On 2016-02-11 10:58 PM, Andrew Barnert via Python-ideas wrote:
>> tl;dr: We should turn dis.Bytecode into a builtin mutable structure similar to byteplay.Code, to make PEP 511 bytecode transformers implementable.
> 
> Big -1 on the idea, sorry.
> 
> CPython's bytecode is the implementation detail of CPython.  PyPy has some opcodes that CPython doesn't have, for example.  Who knows, maybe in CPython 4.0 we won't have code objects at all :)
> 
> Adding something to the standard library means that it will be supported for years to come.  It means that the code is safe to use.  Which, in turn, guarantees that there will be plenty of code that depends on this new functionality.  At first some of that code will be bytecode optimizers, later someone implements LINQ-like extension, and in no time we lose our freedom to work with opcodes.
> 
> If this "new functionality" is something that depends on CPython's internals, it will only fracture the ecosystem.  PyPy, or Pyston, or IronPython developers will either have to support byteplay-like stuff (which might be impossible), or explain their users why some libraries don't work on their platform.

This sounds like potentially a argument against adding bytecode processors in PEP 511.[^1] But if PEP 511 *does* add bytecode processors, I don't see how my proposal makes things any worse. 

Having dis (and inspect, and types.CodeType, and so on) be part of the stdlib makes it easier, not harder, to change CPython without breaking code that may need to introspect it for some reason. In the same way, having a mutable dis would make it easier, not harder, to change CPython without breaking bytecode processors.


  [^1]: Then again, it's just as good an argument against import hooks, and exposing the __code__ member on function objects so decorators can change it, and so on, and years with those features hasn't created a catastrophe...