two options
1. Use ctypes.cdll.LoadLibrary to call directly in python
For the definition of functions in C++ dynamic library, please refer to GCC generation and call dynamic library and static library for the generation of dynamic library
extern "C"{
string c_r(){
return "test0\n";
}
char* c_t(){
return "test1\n";
}
}
call in python
import ctypes
dl=ctypes.cdll.LoadLibrary
lib=dl("./libreply.so")
Because of the type conversion problem, if c_r() is called, it will crash directly
>>> reply=lib.c_r >>> reply() [1] 2618 segmentation fault (core dumped) python
If you want to call c_t(), you need to set the return value type of the function first
>>> reply=lib.c_t >>> reply.restype=ctypes.c_char_p >>> reply() 'test1 \ n' >>> print(reply()) test1
But if it is Chinese, it needs to be decoded again, and a new function that returns the original value is defined.
char* c_reply(char* inputStr){
if(inputStr==NULL)
return "requires input\n";
else
return (char*)string(inputStr).c_str();
}
>>> print(reply("你好").decode("utf-8"))
Hello
If it is not decoded to utf-8, it cannot display Chinese normally
2. Call <Python.h> in the C++ file to encapsulate the functions and classes to be used as python objects, and then use them as a module for python
The C++ file is as follows
#include<iostream>
#include<stdlib.h>
using namespace std;
void printHello(){
cout<<"你好"<<endl;
}
int getInt(int i){
return i;
}
char* getCharArr(char* s){
return s;
}
string getStr(string s){
return s;
}
#include "/usr/include/python2.7/Python.h"//The location of Python.h goes to the place where python is installed
static PyObject * Ext_printHello(PyObject *self, PyObject *args)
{
printHello();
return (PyObject*)Py_BuildValue("");
}
static PyObject * Ext_getInt(PyObject *self, PyObject *args)
{
int num;
if (!PyArg_ParseTuple(args, "i", &num))
return NULL;
return (PyObject*)Py_BuildValue("i", getInt(num));
}
static PyObject * Ext_getCharArr(PyObject *self, PyObject *args)
{
char* s;
if (!PyArg_ParseTuple(args, "s", &s))
return NULL;
return (PyObject*)Py_BuildValue("s", getCharArr(s));
}
static PyObject * Ext_getStr(PyObject *self, PyObject *args)
{
string s;
if (!PyArg_ParseTuple(args, "s", &s))
return NULL;
return (PyObject*)Py_BuildValue("s", getStr(s));
}
static PyMethodDef ExtMethods[] =
{
{ "printHello", Ext_printHello, METH_VARARGS },
{ "getInt", Ext_getInt, METH_VARARGS },
{ "getCharArr", Ext_getCharArr, METH_VARARGS },
{ "getStr",Ext_getStr,METH_VARARGS},
{NULL, NULL},
};
extern "C"{//extern "C" must be added, otherwise the entry function will not be found
void initExt()
{
Py_InitModule("Ext", ExtMethods);
}
}
Compile as dynamic library Ext.so
Called in python, Chinese characters still need to be decoded to utf-8
>>> import Ext
>>> Ext.printHello()
Hello
>>> Ext.getInt(99)
99
>>> Ext.getCharArr("Hello\n")
'\xe4\xbd\xa0\xe5\xa5\xbd\n'
>>> print(Ext.getCharArr("你好\n").decode("utf-8"))
Hello
>>>
& still crashes when calling Ext.getStr(), it seems that the string type is not supported, and can only be converted to a string number with c_str() and then returned
>>> Ext.getStr("hello")
[1] 5347 segmentation fault (core dumped) python
appendix:
