[Python-Dev] Why co_names? Wouldn't be simpler to just use co_consts?

Andrea Griffini agriff at tin.it
Wed Jan 28 19:53:20 CET 2015

The names stored in op_names are totally unrelated as they can be attribute
names, module names, global names; you basically don't know much about them
unless you also inspect the actual bytecode using them (and the same name
can be used in completely different ways in different parts of the same
code object). In my opinion introspection code telling me that the name
`foo` is used but not knowing if it's about a global, a module name or an
attribute name is not going to be that useful, on the other hand if you do
inspect the bytecode then using co_consts doesn't make things more

Anyway I was just curious to know if there was any technical reason (that I
couldn't see) or if it was more a style/historic reason.

Thank you for the clarification

On Wed, Jan 28, 2015 at 1:40 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On 28 January 2015 at 21:21, Greg Ewing <greg.ewing at canterbury.ac.nz>
> wrote:
> > Andrea Griffini wrote:
> >>
> >> Sorry if the question is naive, but why is co_names needed? Wouldn't be
> >> simpler to just use co_consts?
> >
> > One reason might be that keeping them separate means
> > you can have up to 256 names and 256 consts using
> > 1-byte opcode arguments. Otherwise, you'd be limited
> > to a total of 256 of both.
> They're logically distinct things accessed by different opcodes for
> very different purposes. While you theoretically *could* use one array
> to hold both, it would make the eval code harder to read, and various
> introspection tasks (like "tell me all the names referenced from this
> code object") significantly more difficult.
> Cheers,
> Nick.
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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