[Python-Dev] Re: native code compiler? (or, OCaml vs. Python)

[holger krekel]

Guido van Rossum wrote:
> >     Guido> I was thinking of adding appropriate new opcodes for a few
> >     Guido> builtins that are called a lot, like len.  This would be
> >     Guido> implemented using something like this:
> > 
> >     Guido>              case BUILTIN_LEN:
> >     ...
> > 
> > Would you special case those calls so that, in effect, __builtin__.len
> > couldn't be overridden by a "len" object in the globals or locals?
> 
> No, I would only generate a BUILTIN_LEN opcode if there was no local
> or global variable 'len'.
> 
> A few days ago I proposed a restriction on assigning to an attribute
> of a module that stores a new name in that module that is the same as
> the name of a built-in; that was meant to outlaw people doing ugly
> stuff like
> 
>    import random
>    random.len = lambda x: len(x)-1
>    print random.choice([1,2,3])
> 
> and expecting to affect the implementation of choice().
> 
> I don't think anybody would do this on purpose (or even by accident),
> but the possibility exists, and I'd prefer to live without lying awake
> about that case.
> 
> (We could make random.__dict__ read-only, like the new-style class
> __dict__, if you worry about other ways of stuffing unexpected
> variables inside it.

do you mean specifically random.__dict__ or any modules dict? 
If the latter there would be quite some breakage.  It is at least
used for monkey patching modules to make them "unittestable" which
is a valid use case IMO.  Maybe module's dicts could be "frozen" 
by default and this could be explicitely turned off (via a sys-hook).

    holger