RustPython/docs/slides/intro/slide.md

class: center, middle ##Python Interpreter in Rust ###Introduction

2017/3/28

Shing Lyu

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Python's architecture

• Interpreted
• Garbage Collected
• Compiler => bytecode => VM

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Flavors

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Python Flavors

• CPython (THE python)
• Jython (JVM)
• IronPython (.NET)
• Pypy
• Educational
  • Byterun
  • Jsapy (JS)
  • Brython (Python in browser)

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Why rewriting Python in Rust?

• Memory safety

• Learn about Python internal

• Learn real world Rust

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Implementation strategy

• Focus on the VM first, then the compiler
  • Reuse the Python built-in compiler to generate bytecode
• Basic arithmetics
• Control flows (require JUMP)
• Function call (require call stack)
• Built-in functions (require native code)
• Run popular libraries

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References

• dis documentation
• byterun
• byterun (GitHub)
• cpython source code

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How Python VM works

• Stack machine
• Accepts Python bytecode
• python -m dis source.py

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A simple Python code

#!/usr/bin/env python3
print(1+1)

We run python3 -m dis source.py

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The bytecode

  1    0 LOAD_NAME           0 (print)
       3 LOAD_CONST          2 (2)
       6 CALL_FUNCTION       1 (1 positional, 0 keyword pair)
       9 POP_TOP
      10 LOAD_CONST          1 (None)
      13 RETURN_VALUE

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LOAD_NAME "print"

• NAMES = ["print"]
• CONSTS = [None, 2]
• STACK:

 |                    |
 | print (native code)|
 +--------------------+

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LOAD_CONST 2

• NAMES = ["print"]
• CONSTS = [None, 2]
• STACK:

 |                    |
 |          2         |
 | print (native code)|
 +--------------------+

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CALL_FUNCTION 1

1. argument = stack.pop() (argument == 2)
2. function = stack.top() (function == print)
3. call print(2)

• NAMES = ["print"]
• CONSTS = [None, 2]
• STACK:

 |                    |
 | print (native code)|
 +--------------------+

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POP_TOP

• NAMES = ["print"]
• CONSTS = [None, 2]
• STACK:

 |                    |
 |     (empty)        |
 +--------------------+

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LOAD_CONST 1

• NAMES = ["print"]
• CONSTS = [None, 2]
• STACK:

 |                    |
 |       None         |
 +--------------------+

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RETURN_VALUE

(returns top of stack == None)

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Next step

• Make it run a small but popular tool/library
• Implement the parser
• Performance benchmarking