python编程（多线程c回调python）

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python下面的GIL决定了每次thread执行的时候不能实现完全的并发执行。所以如果多线程c调用python代码的时候，有很多地方需要注意一下。

1、开始处添加多线程支持

// threads launched after everything is okPyEval_InitThreads();

2、在子线程创建之前，主线程释放控制权

PyEval_ReleaseThread(PyThreadState_Get());

3、子线程创建之前必须完成其他所有操作

Py_Initialize();if (!Py_IsInitialized()) return -1; PyRun_SimpleString("import sys"); PyRun_SimpleString("sys.path.append('./')");//import Module pModule = PyImport_ImportModule("hello");if (!pModule) {printf("Can't import Module!/n"); return -1;}

4、子线程调用python的时候先用锁保护好

PyGILState_STATE gstate;gstate = PyGILState_Ensure();PyObject* pFun = PyObject_GetAttrString(pModule, "show"); PyObject_CallFunction(pFun, "s", param_name);Py_DECREF(pFun);PyGILState_Release(gstate);

5、子线程结束后交还给主线程时，最好再次锁住虚拟机

PyGILState_Ensure(); Py_DECREF(pModule); //Release Py_Finalize();

6、完整流程如下所示，

#include <stdio.h> #include <pthread.h> #include <unistd.h> #include <stdlib.h> #include <signal.h>#include <Python.h>int g_exit = 0;PyObject* pModule;void sig_process(int sig) { g_exit = 1;} void func(void* param_name) { while(!g_exit){PyGILState_STATE gstate;gstate = PyGILState_Ensure();PyObject* pFun = PyObject_GetAttrString(pModule, "show"); PyObject_CallFunction(pFun, "s", param_name);Py_DECREF(pFun);PyGILState_Release(gstate);}} int main() { pthread_t pid1, pid2, pid3; signal(SIGINT, sig_process); Py_Initialize();if (!Py_IsInitialized()) return -1; PyRun_SimpleString("import sys"); PyRun_SimpleString("sys.path.append('./')");//import Module pModule = PyImport_ImportModule("hello");if (!pModule) {printf("Can't import Module!/n"); return -1;} // threads launched after everything is okPyEval_InitThreads(); PyEval_ReleaseThread(PyThreadState_Get()); if(pthread_create(&pid1, NULL, (void *(*)(void *))func, "output")) { return -1; } if(pthread_create(&pid2, NULL, (void *(*)(void *))func, "show")){ return -1; } if(pthread_create(&pid3, NULL, (void *(*)(void *))func, "see")){ return -1; } while(!g_exit){ sleep(3); } pthread_join(pid3, NULL);pthread_join(pid2, NULL);pthread_join(pid1, NULL);PyGILState_Ensure(); Py_DECREF(pModule); //Release Py_Finalize();return 0; }

其中编译方法为，

gcc process.c -I/usr/include/python2.7 -ldl -lutil -lpthread -lpython2.7 -o process

而python脚本文件内容为，

def show(name): print 'hello ' + name