Home Original page

[Python-Dev] Accessing globals without dict lookup

Jason Orendorff jason@jorendorff.com
Fri, 8 Feb 2002 22:09:59 -0600 
Guido van Rossum wrote:
> - Let a cell be a really simple PyObject, containing a PyObject
>   pointer and a cell pointer.  Both pointers may be NULL.  (It may
>   have to be called PyGlobalCell since I believe there's already a
>   PyCell object.)  (Maybe it doesn't even have to be an object -- it
>   could just be a tiny struct.)
> 
> - Let a celldict be a mapping that is implemented using a dict of
>   cells.  When you use its getitem method, the PyObject * in the cell
>   is dereferenced, and if a NULL is found, getitem raises KeyError
>   even if the cell exists.  Using setitem to add a new value creates a
>   new cell and stores the value there; using setitem to change the
>   value for an existing key stores the value in the existing cell for
>   that key.  There's a separate API to access the cells.

The following is totally unimportant, but I feel compelled to share:

I implemented this once, long ago, for Python 1.5-ish, I believe.  I got
it to the point where it was only 15% slower than ordinary Python, then
abandoned it.  ;)  In my implementation, "cells" were real first-class
objects, and "celldict" was a copy-and-hack version of dictionary.  I
forget how the rest worked.

Anyway, this is all very exciting to me.  :)

## Jason Orendorff    http://www.jorendorff.com/