[Python-Dev] Accessing globals without dict lookup

2002年2月11日 08:39:35 -0600

 Ping> All right -- i have attempted to diagram a slightly more
 Ping> interesting example, using my interpretation of Guido's scheme.
Very nice. One case I would like to see covered is that of a global that is
deleted. Something like:
 import eggs
 i = -2
 max = 3
 j = 4
 def foo(n):
 y = abs(i) + max
 return eggs.ham(y + n)
 del j
I presume there would still be an entry in spam's module dict with a NULL
objptr.
The whole think makes sense to me if it avoids the possible two
PyDict_GetItem calls in the LOAD_GLOBAL opcode. As I understand it, if
accessed inside a function, LOAD_GLOBAL could be implemented something like
this:
 case LOAD_GLOBAL:
 cell = func_cells[oparg];
 if (cell.objptr) x = cell->objptr;
 else x = cell->cellptr->objptr;
 if (x == NULL) {
 ... error recovery ...
 break;
 }
 Py_INCREF(x);
 continue;
This looks a lot better to me (no complex function calls).
What happens in the module's top-level code where there is presumably no
func_cells array? Do we simply have two different opcodes, one for use at
the global level and one for use in functions?
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