Integrate Python implementations of a C interface into an existing C program, allowing Python implementations to be used seamlessly within the larger program.
Consider the following C interface definition:
<code class="cpp">class myif { public: virtual float myfunc(float a) = 0; };</code>
Enable Polymorphism with SWIG:
%module(directors="1") module %include "myif.h"
Create a Python Implementation:
<code class="python">import module class MyCl(module.myif): def __init__(self): module.myif.__init__(self) def myfunc(self, a): return a * 2.0</code>
Initialize Python (main.cc):
<code class="cpp">Py_Initialize();</code>
Import the Python Module:
<code class="cpp">PyObject *module = PyImport_Import(PyString_FromString("mycl"));</code>
Create Instance and Execute Function:
<code class="cpp">PyObject *instance = PyRun_String("mycl.MyCl()", Py_eval_input, dict, dict); double ret = PyFloat_AsDouble(PyObject_CallMethod(instance, "myfunc", (char *)"(O)" ,PyFloat_FromDouble(input)));</code>
Finalization:
<code class="cpp">Py_Finalize();</code>
Exposing SWIG Runtime:
swig -Wall -c++ -python -external-runtime runtime.h
Recompile SWIG Module:
g++ -DSWIG_TYPE_TABLE=myif -Wall -Wextra -shared -o _module.so myif_wrap.cxx -I/usr/include/python2.7 -lpython2.7
Helper Function for Conversion:
<code class="cpp">myif *python2interface(PyObject *obj) { ... }</code>
<code class="cpp">int main() { ... myif *inst = python2interface(instance); std::cout << inst->myfunc(input) << std::endl; ... }</code>
By following these steps, one can successfully implement Python implementations of a C interface and seamlessly integrate them into larger C programs, providing greater flexibility and extensibility.
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