Making The Case For A (Semi) Formal Specification Of CPython
The CPython implementation has grown and evolved significantly over the past ~25 years. In that time there have been many other projects to create compatible runtimes for your Python code. One of the challenges for these other projects is the lack of a fully documented specification of how and why everything works the way that it does. In the most recent Python language summit Mark Shannon proposed implementing a formal specification for CPython, and in this episode he shares his reasoning for why that would be helpful and what is involved in making it a reality.
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- Your host as usual is Tobias Macey and today I’m interviewing Mark Shannon about his efforts to create a formal specification for the CPython interpreter
- How did you get introduced to Python?
- Can you start by describing the current state of how the Python language and the CPython runtime are defined?
- What is your motivation in advocating for a specification?
- After ~25 years of the language, why is now the time to pursue this effort?
- How does the history of the language and the scope of the ecosystem and community impact the effort required to make this a reality?
- What is involved in creating the specification and where would it be located once complete?
- What are some examples of languages that are formally specified?
- What are the possible benefits of creating a specification for the CPython virtual machine?
- What is the distinction between a specification for the VM as opposed to a specification for the language?
- What are some potential downsides to having a (semi-)formal specification become part of the definition of the interpreter?
- Can you describe the process of doing the work to create the specification?
- How are you approaching the actual definition of the specification (e.g. prose vs programmatic)?
- What are the tradeoffs of prose vs. an executable specification (e.g. TLA+, Alloy)?
- How does this work tie into your goals of improving the speed of the CPython interpreter?
- What are some of the most interesting, unexpected, or challenging aspects of your efforts to bring this specification to CPython?
- How can the community contribute to this effort?
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