"Pierre-Yves Martin" <pym.aldebaran@gmail.com> wrote:
Currently it's possible to customize attribute access via methods :
__getattribute__(self, name) __getattr__(self, name) __setattr__(self, name, value)
but it is not possible to customize local variable access. It would be useful for example to allow implementation of a local constant or any other on-access/on-modification behavior. The function should could be: [snip]
To offer the ability to control such access in a function-local scope would result in significant slowdown during the execution of the function body. This issue would propagate everywhere, as with your offered semantics, every name lookup would result in a function call (except for the __getlocal__ and __setlocal__ lookups apparently), and function calls in Python are significantly slower than dictionary lookups (globals, etc.) or array lookups (function local accesses). There are many other reasons to dislike your proposal, but in an attempt to get something done today, I'll restrain myself.
#Sample 2 : Constants [snip]
I believe this is the wrong approach. If you want to define constants, create a class with read-only properties. Alternatively, recent Pythons allow for passing a dict subclasses to the global and local dictionaries in the exec statement which implement your constant definitions. Both options can offer read-only constants, are available *now*, and even better, won't destroy the performance of Python. If you couldn't guess, -1 . - Josiah