Pointers and smart pointers
Since Python handles memory allocation and garbage collection automatically, the concept "pointer" is not meaningful within Python. However, many C++ API exposes either raw pointers or shared pointers, and to wrap such APIs one would need to deal with pointers.
Pointers (raw C++ pointers)
The life time of C++ objects created by "new A" kan be handled by Pythons garbage collection by using the manage_new_object storage policy:
{{{struct A {
- static A* create () { return new A; } std::string hello () { return "Hello, is there anybody in there?"; }
};
BOOST_PYTHON_MODULE(shared_ptr) {
class_<A>("A",no_init)
def("create",&A::create,return_value_policy<manage_new_object>())
- staticmethod("create")
def("hello",&A::hello) ;
} }}}
A sample python program:
from pointer import * an_A = A.create() print an_A.hello()
Smart pointers
Smart pointers, e.g. boost::shared_ptr<T>, is another common way to give away ownership of objects in C++. Theese kind of smart pointer are automatically handled, if you declare their existence, when declaring the class to boost.python.
E.g.
{{{#include <boost/shared_ptr.h> using namespace boost;
struct A {
static shared_ptr<A> create () { return shared_ptr<A>(new A); } std::string hello () { return "Just nod if you can hear me!"; }
};
BOOST_PYTHON_MODULE(shared_ptr) {
class_<A, shared_ptr<A> >("A",init<>())
def("create",&A::create )
- staticmethod("create")
def("hello",&A::hello)
} }}}
A sample python program:
from shared_ptr import * an_A = A.create() print an_A.hello()