The EXTENDED_ARG is included in the multibyte ops, I treat it just like any other operator.  Here's a snippet of my hacked-dis.dis output, which made it clear to me that I could just count them as an "operator with word operand."

Line 3000: x = x if x or not x and x is None else x
0001dc83 7c 00 00         LOAD_FAST           x
0001dc86 91 01 00         EXTENDED_ARG        1
0001dc89 70 9f dc         JUMP_IF_TRUE_OR_POP L1dc9f
0001dc8c 7c 00 00         LOAD_FAST           x
0001dc8f 0c               UNARY_NOT
0001dc90 91 01 00         EXTENDED_ARG        1
0001dc93 6f 9f dc         JUMP_IF_FALSE_OR_POPL1dc9f
0001dc96 7c 00 00         LOAD_FAST           x
0001dc99 74 01 00         LOAD_GLOBAL         None
0001dc9c 6b 08 00         COMPARE_OP          'is'
0001dc9f 91 01 00         EXTENDED_ARG        1
0001dca2 72 ab dc         POP_JUMP_IF_FALSE   L1dcab
0001dca5 7c 00 00         LOAD_FAST           x
0001dca8 6e 03 00         JUMP_FORWARD        L1dcae (+3)
0001dcab 7c 00 00         LOAD_FAST           x
0001dcae 7d 00 00         STORE_FAST          x

On Wed, Apr 13, 2016 at 2:23 PM, Victor Stinner <> wrote:
2016-04-13 23:02 GMT+02:00 Eric Fahlgren <>:
> Percentage of 1-byte args    = 96.80%

Yeah, I expected such high ratio. Good news that you confirm it.

> Non-argument ops             =    53,719
> One-byte args                =   368,787
> Multi-byte args              =    12,191

Again, only a very few arguments take multiple bytes. Good, the
bytecode will be smaller.

IMHO it's more a nice side effect than a real goal. The runtime
performance matters more than the size of the bytecode, it's not like
a bytecode take 4 MB. It's probably closer to 1 KB and so can probably
benefit of the fatest CPU caches.

> Just for the record, here's my arithmetic:
> byteCodeSize     = 1*nonArgumentOps + 3*oneByteArgs + 3*multiByteArgs
> wordCodeSize     = 2*nonArgumentOps + 2*oneByteArgs + 4*multiByteArgs

If multiByteArgs means any size > 1 byte, the wordCodeSize formula is wrong:

- no parameter: 2 bytes
- 8-bit parameter: 2 bytes
- 16-bit parameter: 4 bytes
- 24-bit parameter: 6 bytes
- 32-bit parameter: 8 bytes

But you wrote that you didn't see EXTEND_ARG, so I guess that
multibyte means 16-bit in your case, and so your formula is correct.

Hopefully, I don't expect 32-bit parameters in the wild, only 24-bit
parameter for function with annotation.

> (It is interesting to note that I have never encountered an EXTENDED_ARG operator in the wild, only in my own synthetic examples.)

As I wrote, EXTENDED_ARG can be seen when MAKE_FUNCTION is used with