Re: [Boost-users] Boost::python readonly access to nonconstant class members

Subject: Re: [Boost-users] Boost::python readonly access to nonconstant class members
From: Dave Abrahams (dave_at_[hidden])
Date: 2010-12-21 14:14:43

At Tue, 21 Dec 2010 15:47:38 +0100,
Ralf Goertz wrote:
> 
> Hi,
> 
> is it possible to have python have readonly access to class members
> that are non constant?
> 
> typedef map<string,string> Links;
> 
> class DataSet {
> 	Links links;
> }
> 
> BOOST_PYTHON_MODULE(_boosttest) {
>     class_<Links>("Links")
>         .def(map_indexing_suite<Links>());
> 
>     class_<DataSet>("DataSet")
>         .def_readonly("links",&DataSet::links);
> }
> 
> Although DataSet.links is defined readonly I can change it from within
> python. 

If you mean that you can do

   d = DataSet()
   d.links = 1

that would be a Boost.Python bug.

If instead you mean that you can do 

   d = DataSet()
   d.links["foo"] = "bar"

that would be unsurprising (to me), intended behavior; that's just how
the Python object model works.  

> What can I do to prevent python from overwriting links?

You could always do the equivalent of

  del DataSet.__dict__["__setitem__"]

to disable it.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com