[C++-sig] Vector of abstract class pointers with boost::python

Benjamin Kloster benkloster at googlemail.com
Fri Jan 9 20:04:02 CET 2009

Hi everyone,
I have the following problem: an abstract base class A that is
exported to python and another class, let's call it L, that is little
more than a glorified vector of A's with a few convenience functions.
The constructor of L is passed a std::vector<A*>. Now I would like to
export L to Python with the following conditions:
1. The __init__ function of L should take a Python list containing sub
classes of A that is automatically converted to a vector of A pointers
2. The L instance takes ownership of the A's (they are deleted in the

Since I have to write a wrapper for L anyway (for virtual functions
with default implementation), I tried giving the wrapper class a
constructor like so:

LWrapper(boost::python::object o) {
    boost::python::list listOfAs = extract<boost::python::list>(o);
    try {
        bool is_ok = true;
        while(is_ok) {
            extract<A*> a(listOfAs.pop(0))
            if(a.check()) {
                vectorOfAs.push_back(a()) // vectorOfAs is a protected
class member of L
            else {
              is_ok = false;
    catch(exception &e) {
      std::cerr << "Oops!";

But this crashes with "glibc dected [...] free(): invalid pointer [...]".

So. How would I actually go about doing this?

Thanks in advance,
Benjamin Kloster

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