[Python-Dev] towards a faster Python

[Skip Montanaro]

    Skip> I was thinking more along the lines of making the dict itself
    Skip> read-only.

    Fred> That certainly makes global variables more difficult, doesn't it?

Yes, but we all know globals are bad, right? ;-)

At first blush, it doesn't seem all that tough to worm around this in the
interpreter (postulating a read_only flag for dicts or at least for that
variety of dict used as a module dict):

    case STORE_GLOBAL:
            w = GETITEM(names, oparg);
            v = POP();
            ro = f->f_globals->read_only;
            f->f_globals->read_only = 0;
            err = PyDict_SetItem(f->f_globals, w, v);
            f->f_globals->read_only = ro;
            Py_DECREF(v);
            break;

or something like that.  I think the STORE_GLOBAL instruction will only be
executed to set a global in the current module.  Any foreign setting,
e.g. "fileinput.open = 10", will be handled by STORE_ATTR.  Can executing
PyDict_SetItem() cause arbitrary Python code to execute?

(I'm almost purposely adopting an XP approach here - do just enough to
address the current breakage and see what the next problem is which pops
up.)

Skip