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

[Guido van Rossum]

> > >     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? 

Any module's 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.

Why would this be done by patching the module's __dict__ rather than
assigning to attributes of the module?

> Maybe module's dicts could be "frozen" by default and this could be
> explicitely turned off (via a sys-hook).

What I proposed was only closing off write access to the __dict__ so
that the setattr code for type module can implement certain
restrictions (e.g. no assignment to attributes named "len").

--Guido van Rossum (home page: http://www.python.org/~guido/)