The document discusses how CPython creates bytecode from Python source code by tokenizing, parsing, building a symbol table, and compiling to bytecode. It provides an example of using the dis module to disassemble bytecode and lists some example bytecode instructions. It notes that the Python virtual machine is stack-based and that understanding bytecode can provide optimizations like using fewer or more specialized bytecode instructions to make code run faster.

1. Dive into CPython Bytecode Alex Gaynor

2. I don't need to know that stuff

3. You don't. But it's totally helpful.

4. How does CPython Make Bytecode?

5. Tokenize the source

6. Parse the tokens into an AST

7. Build a symbol table to figure out what's a global

8. Compile to bytecode

9. Now I can haz bytecode

10. Now that I has a bytecode how does I see it?

11. >>> def f(o): ... return o >>> import dis >>> dis.dis(f) 2 0 LOAD_FAST 0 (o) 3 RETURN_VALUE

12. So use the dis module

13. So now that we have bytecode, what do we do with it?

14. Well, what are those bytecodes?

15. A few examples UNARY_NEGATIVE: -TOS BINARY_ADD: TOS1 + TOS SLICE+3: TOS2[TOS1:TOS] UNPACK_SEQUENCE LOAD_CONST CALL_FUNCTION_VAR_KW

16. Python VM is stack based

17. So now we know some bytecodes, what can we do with this knowledge

18. A tale of 2 functions >>> def f(): ... return [x for x in xrange(10)] >>> def g(): ... o = [] ... for x in xrange(10): ... o.append(x) ... return o

21. Less Bytecode == faster!

22. More specialized bytecodes == faster

23. @alex_gaynor Thanks