[Tutor] bytecode primer, and avoiding a monster download

[Oscar Benjamin]

On 28 May 2013 18:24, eryksun <eryksun at gmail.com> wrote:
> On Tue, May 28, 2013 at 1:12 PM, Oscar Benjamin
> <oscar.j.benjamin at gmail.com> wrote:
>> On 28 May 2013 17:48, eryksun <eryksun at gmail.com> wrote:
>>>
>>> The argument for dis.dis() can be a module, class, function or code
>>> object. It disassembles all the top-level code objects that it finds,
>>> but it doesn't recursively disassemble code objects that are in the
>>> co_consts.
>>
>> What do you mean by this? I tried passing a test module into dis.dis
>> and nothing happens:
>
> Obviously dis() has nothing to do if the module or class namespace has
> no code objects to disassemble.
>
> Did you read the rest of my post?

Yes. Although I'll admit that I didn't fully absorb all of it. :)

> I went through an example of loading
> the cached code object from a .pyc. But we can just compile one
> instead:

Okay, got you. So the way to dis an ordinary module is to load the .py
file as a string first:

>>> dis.dis(compile(open('tmp.py').read(), 'tmp', 'exec'))
  2           0 LOAD_CONST               0 (1)
              3 STORE_NAME               0 (a)

  3           6 LOAD_CONST               1 (2)
              9 STORE_NAME               1 (b)

  4          12 LOAD_NAME                0 (a)
             15 LOAD_NAME                1 (b)
             18 BINARY_ADD
             19 STORE_NAME               2 (c)
             22 LOAD_CONST               2 (None)
             25 RETURN_VALUE

So what happens to the code object for the top-level code in the
module itself when it is imported in the normal way? Is it just
discarded once import is complete? Is it temporarily accessible during
import?


Oscar