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

From: Ullrich Koethe (koethe_at_[hidden])
Date: 2000-11-27 14:06:48

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 ?

Ragards
Ulli
-- 
 ________________________________________________________________
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| Ullrich Koethe  Universität Hamburg / University of Hamburg    |
|                 FB Informatik / Dept. of Computer Science      |
|                 AB Kognitive Systeme / Cognitive Systems Group |
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