Hi,
I’m wrapping a 3rd party library using boost.python and I’m bumping into a
frustrating pattern. The library has derived classes which overload methods
in their base class. They do properly expose the base class’ methods using
“using”, but, when I try to wrap all of these derived classes, python
doesn’t see the base class’ method through an instance of the derived
class. Here’s an example:
#include <boost/python.hpp>
using namespace boost::python;
struct A {
virtual void foo(int a) {}
virtual void bar(double b) {}
};
struct B : A {
virtual void foo(int a, double b) {}
};
BOOST_PYTHON_MODULE(broken)
{
class_<A>(“A”)
.def(“foo”, &A::foo)
.def(“bar”, &A::bar)
;
class_<B, bases<A> >(“B”)
.def(“foo”, &B::foo)
;
}
Then in python:
import broken
a = broken.A()
b = broken.B()
a.foo(1)
a.bar(2.0)
b.foo(1,2.0)
b.bar(2.0)
b.foo(0)
Running this I get (as you’ve probably already guessed):
File “.../test.py”, line 11, in <module>
b.foo(0)
Boost.Python.ArgumentError: Python argument types in
B.foo(B, int)
Did not match C++ signature:
foo(B {Value}, int, double)
I’m not surprised by this behavior given python’s method resolution
process. My question is whether there’s a good way to deal with this in
boost.python so that I don’t have to add duplicate entries in sub-classes
for methods I’ve already exposed in base classes.
Thanks,
Jeremy
