python - 使用python事件并与c++交互

Question

我正在测试在C / C++程序中嵌入Python，但是我缺乏理解。

测试程序很简单:

初始化解释器；

从启动Timer的文件中执行python脚本(每0.1秒增加一个变量)；

等待5秒(C++);

从字符串执行python脚本，该脚本显示由Timer

事件产生的值

等待5秒(C++);

完成；

我观察到Timer事件是在方法Py_FinalizeEx()的调用期间执行的； ;

所以:

c++程序在方法Py_FinalizeEx()处停止；

，C++程序无法与Py_FinalizeEx()之前或之后的事件进行交互；

在事件循环期间，C++程序如何与Python程序交互？

python代码:

from threading import *

count = 0;

def foo():
    global count
    t = Timer(0.1, foo)
    t.start()
    count= count+1;
    print("foo " + str(count), flush=True)

foo()

C++代码

// initialize
Py_InitializeEx(0);

// execute foo.py
PyRun_SimpleStringFlags("exec(open('foo.py'.encode('utf-8')).read())",nullptr);

// wait 5s
qDebug() << "wait 1 begin";
QTime t = QTime::currentTime().addSecs(5);
while(t > QTime::currentTime());
qDebug() << "wait 1 end";

// display value
PyRun_SimpleStringFlags("print(count)",nullptr);

// wait 5s
qDebug() << "wait 2 begin";
t = QTime::currentTime().addSecs(5);
while(t > QTime::currentTime());
qDebug() << "wait 2 end";

qDebug() << "finalize: begin";
Py_FinalizeEx();;
qDebug() << "finalize: end";

结果:

foo 1
wait 1 begin
wait 1 end
wait 2 begin
1
wait 2 end
finalize: begin
foo 2
foo 3
foo 4
foo 5
foo 6
foo 7
foo 8
foo 9
foo 10

Answer 1

伊卡洛斯的解决方案对我有帮助:

Surround your "wait begin" and "wait end" with Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS

这些宏对应于以下代码:

// Py_BEGIN_ALLOW_THREADS
{
  PyThreadState *save
  save = PyEval_SaveThread();
// -------------
  qDebug() << "wait 1 begin";
  QTime t = QTime::currentTime().addSecs(5);
  while(t > QTime::currentTime());
  qDebug() << "wait 1 end";
// Py_END_ALLOW_THREADS
  PyEval_RestoreThread(save);
}
// --------------

我用Qt事件开发了另一个版本:

from threading import *

count = 0;

def foo():
    global count
    if count < 20:
        t = Timer(1, foo)
        t.start()
    count= count+1;
    print("foo " + str(count), flush=True)

foo()

#ifndef TEST_H
#define TEST_H

#include <QObject>
#include <QTimer>

#undef slots
#include <Python.h>
#define slots

class PythonTest : public QObject
{
    Q_OBJECT

    PyThreadState *save;

    QTimer _timer;
    int count = 0;

public:
    explicit PythonTest(QObject *parent = nullptr);

signals:

public slots:
    void read();
    void stop();
};

#endif // TEST_H

#include "pythontest.h"
#include <QDebug>

PythonTest::PythonTest(QObject *parent) : QObject(parent)
{
    qDebug() << "start: begin";
    Py_InitializeEx(0);

    PyRun_SimpleStringFlags("exec(open('foo.py'.encode('utf-8')).read())",nullptr);

    _save = PyEval_SaveThread();

    _timer.setInterval(5000);
    QObject::connect(&_timer, &QTimer::timeout, this, &PythonTest::read);
    _timer.start();

    qDebug() << "start: end";
}

void PythonTest::read()
{
    qDebug() << "read: begin";
    if(_count>10)
    {
        QObject::disconnect(&_timer, &QTimer::timeout, this, &PythonTest::read);
        QObject::connect(&_timer, &QTimer::timeout, this, &PythonTest::stop);
    }

    PyEval_RestoreThread(_save);
    PyRun_SimpleStringFlags("print('read ' + str(count),flush=True)");
    _save = PyEval_SaveThread();

    _count++;
    qDebug() << "read: end";
}

void PythonTest::stop()
{
    qDebug() << "stop: begin";
    QObject::disconnect(&_timer, &QTimer::timeout, this, &PythonTest::stop);
    PyEval_RestoreThread(_save);

    Py_FinalizeEx();
    qDebug() << "stop: end";
}

输出:

start: begin
foo 1
start: end
foo 2
foo 3
foo 4
foo 5
foo 6
read: begin
read: end
read6
foo 7
foo 8
foo 9
foo 10
read: begin
read: end
read10
foo 11
foo 12
foo 13
foo 14
foo 15
read: begin
read: end
read15
foo 16
foo 17
foo 18
foo 19
foo 20
read: begin
read: end
read20
foo 21
read: begin
read: end
read21
read: begin
read: end
read21
read: begin
read: end
read21
...