从.cpp文件导入函数到python

Question

Let me start with a disclaimer that i'm putting this question after lot of research and not finding any direct and step by step example.

Have gone through Cython , SWIG, Boostpython documentation but couldn't get a step by step process and so posting here -

I have a .cpp & .h file with couple of mathematical functions defined.I want to call them in a python (.py) code file.

How do i integrate?Which is the best and neatest way to go about it. Please illustrate

Answer 1

See this part of the Cython documentation; it takes you step-by-step through interfacing with a C library.

Answer 2

Since i eventually solved it using some of the help provided here and research , let me post the answer.

I did the import of CPP function via Python using Cython.

Cython wraps the Python code with CPP file and compiles the two. The outcome is a Python module (name of the module can be specified in setup.py file ) and the module can be called as usual.

The issue i was facing was calling a CPP function from Python.So here are my tips for working it out

1. Define your function in C++ Header and CPP file.
2. Using cdef , define the function in Python script in the beginning where you import modules define other variables.This definition is similar to C++ header file definition
3. While pasing arguments and arrays to the function call from python , ensure all variables and arrays are type casted as CPP.
4. For arrays, it is a bit tricky. EG a double array in Python can be type casted using array.array(array_to_cast) . In the following example, we cast the python array, dev , into the c++ array, dev_arr . Note that dev is an array of type double in python, hence the first parameter input to array.array() is 'd' .

cdef array.array dev_arr = array.array('d',dev)   

While passing the dev_arr array to your main CPP function, you have to specify this array : data.as_doubles

fn_response = cpp_fn_call(stddev_arr.data.as_doubles,...)

Rest will work smoothly.