Re: [boost] py_cpp and vector<..>::const_iterator

From: Anton Gluck (gluc_at_[hidden])
Date: 2000-11-29 00:39:03

Ullrich,

On Mon, 27 Nov 2000, Ullrich Koethe wrote:

> Petr Kocmid wrote:
> > 
> > > Don't expose iterators. Python has its own iteration idioms (e.g.
> > > "for x in
> > > S"), so just support the python sequence interface on your vector. Since
> > > your vector is a random-access container, this will be fast. I reccommend
> > > this approach.
> > 
> > I predict the problem Anton had will arise many times in the future. Perhaps
> > we can
> > add some generic conversion of STL containers to sequence/mapping protocol
> > to py_cpp.
> > 
> 
> 
> I've implemented and successfully tested the following "Cursor"-feature
> to wrap STL iterators:
> 
> in C++:
> 	
>     typedef std::list<Foo> FooList;
>     boost::python::class_builder<FooList> foolist_class(my_module,
> "FooList");
>     foolist_class.def(boost::python::constructor<>());
>     foolist_class.def((void (FooList::*)(Foo const
> &))&FooList::push_back, "append");
>     
>     // define a cursor for FooLists
>     my_module.def_cursor_for(foolist_class);  
> 
> Then in Python:
> 
>     >>> fooList = FooList()
>     >>> fooList.append(Foo(1))
>     >>> fooList.append(Foo(2))
>     >>> 
>     >>> for i in fooList.cusor(): # use cursor in a loop
>     ...     i
>     ...     print i.getData()
>     ...
>     <Foo object at 111070>
>     1
>     <Foo object at 1110e8>
>     2
>     >>>
>     >>> c = fooList.cursor()
>     >>> c[1].getData()   # use cursor to read and write the data
>     2
>     >>> c[1] = Foo(4)
>     >>> c[1].getData()
>     4
> 
> Would this suit your needs ?

I'm not sure if this was meant for me or Petr. I can see useful parts
here when creating an iterator, but can't see how it helps exposing an
existing iterator. I guess the magic is happening in
"my_module.def_cursor_for(foolist_class);"?

Gruesse,

Toni