Safe eval?

[Alex Martelli]

gbreed at cix.compulink.co.uk wrote:

> Chris Liechti wrote:
> 
>> you can disable the builtin functions you want and populate the
>> namespace with save functions and classes (see Bastion for that)
> 
> I've never worked out how to do the second bit.  Bastion you say?  The
> documentation for that's all about restricting access to classes.  How do
> I get such a class into the namespace for an reval?  Every time this comes
> up, somebody says "use reval" but nothing about how you supply locals to

Nice overview at:
http://py-howto.sourceforge.net/txt/rexec.txt

The key point you ask about:

"""
module = r_env.add_module(module_name)
mod_dict = module.__dict__    Despite its name, the add_module() method 
actually only adds the
   module if it doesn't already exist; it returns the corresponding
   module object, whether or not the module had to be created.
  
   Most commonly, you'll insert variable bindings into the __main__ or
   __builtins__ module, so these will be the most frequent values of
   module_name.
  
   Once you have the module's dictionary, you need only insert a
   key/value pair for the desired variable name and value. For example,
   to add a username variable:
  
mod_dict['username'] = "Kate Bush"    Restricted code will then have access 
to this variable.
"""


Alex