[Python-Dev] Can Python implementations reject semantically invalid expressions? (original) (raw)

Craig Citro craigcitro at gmail.com
Fri Jul 2 16:44:08 CEST 2010

Whoa.  That's very peculiar looking bytecode.  Is dis.dis behaving as it should here? BTW, I think you want 'raise TypeError', not 'raise TypeError()'.

Yep, that's embarrassing. I was being lazy: I was expecting different bytecodes, and I got it ... so I apparently didn't bother to actually read the bytecodes? It's interesting -- if I'd just had TypeError instead of TypeError(), I would have found this out, because "raise TypeError" is not the bytes representation of a valid sequence of bytecodes. ;)

Anyway, here's what I was going for:

def foo(): ... return 1+'1' ... def bar(): ... raise TypeError ... dis.dis(foo) 2 0 LOAD_CONST 1 (1) 3 LOAD_CONST 2 ('1') 6 BINARY_ADD 7 RETURN_VALUE dis.dis(bar) 2 0 LOAD_GLOBAL 0 (TypeError) 3 RAISE_VARARGS 1 6 LOAD_CONST 0 (None) 9 RETURN_VALUE

That said, I totally concede Martin's point -- this is an implementation-specific thing. It happens that all the major Python implementations compile to some VM, and I'd bet that these two compile to different bytecodes on any of them, but that doesn't preclude another implementation from making a different choice there.

-cc

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