How to use C++ classes with ctypes?

Question

Hi there,

I'm just getting started with ctypes and would like to use a C++ class that I have exported in a dll file from within python using ctypes. So lets say my C++ code looks something like this:

class MyClass {
  public:
    int test();
...

I would know create a .dll file that contains this class and then load the .dll file in python using ctypes. Now how would I create an Object of type MyClass and call its test function? Is that even possible with ctypes? Alternatively I would consider using SWIG or Boost.Python but ctypes seems like the easiest option for small projects.

Any help is appreciated,

Jörg

Answer 1

The short story is that there is no standard binary interface for C++ in the way that there is for C. Different compilers output different binaries for the same C++ dynamic libraries, due to name mangling and different ways to handle the stack between library function calls.

So, unfortunately, there really isn't a portable way to access C++ libraries in general. But, for one compiler at a time, it's no problem.

This blog post also has a short overview of why this currently won't work. Maybe after C++0x comes out, we'll have a standard ABI for C++? Until then, you're probably not going to have any way to access C++ classes through Python's ctypes.