Subclassed dict as globals

[Evan Simpson]

In Python 2.4 the following works:

class G(dict): .... def __getitem__(self, k):
.... return 'K' + k
.... g = G()
exec 'print x, y, z' in g Kx Ky Kz

....while in Python 2.3 it fails with NameError: name 'x' is not defined.
Is this an "accidental feature", or can I count on this working in
future versions of Python? For that matter, is there a way to do this
(intercept global variable accesses) in Python 2.3?

Cheers,

Evan @ 4-am

[Lenard Lindstrom]

Evan Simpson <ev**@tokenexchange.com> writes:

In Python 2.4 the following works:

>>> class G(dict): ... def __getitem__(self, k):
... return 'K' + k
... >>> g = G()
>>> exec 'print x, y, z' in g Kx Ky Kz >>> [snip] [Is] there a way to do this (intercept global variable accesses)
in Python 2.3?

One can emulate it in a rather limited way in pre 2.4 releases:

cd = compile("print x, y, z", '<string>', 'exec')
glbs = dict(globals())
for id in cd.co_names: glbs[id] = 'K' + id

exec cd in glbs

Kx Ky Kz

Special names can be used only as constants. It is better suited
for eval() than exec.

Lenard Lindstrom
<le***@telus.net>