[Python-Dev] PEP 575, 576, 579 and 580

Mark Shannon mark at hotpy.org
Sat Jul 7 09:38:39 EDT 2018


We seem to have a plethora of PEPs where we really ought to have one (or 

Traditionally when writing a new piece of software, one gathered 
requirements before implementing the code. Let us return to that 
venerable tradition.

IMO, mailing lists are a terrible way to do software design, but a good 
way to gather requirements as it makes less likely that someone will be 

So, let us gather the requirements for a new calling API.

Here are my starting suggestions:

1. The new API should be fully backwards compatible and shouldn't break 
the ABI
2. The new API should be used internally so that 3rd party extensions 
are not second class citizens in term of call performance.
3. The new API should not prevent 3rd party extensions having full 
introspection capabilities, supporting keyword arguments or another 
feature supported by Python functions.
4. The implementation should not exceed D lines of code delta and T 
lines of code in total size. I would suggest +200 and 1000 for D and T 
respectively (or is that too restrictive?).
5. It should speed up CPython for the standard benchmark suite.
6. It should be understandable.

What am I missing? Comments from the maintainers of Cython and other 
similar tools would be appreciated.


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