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使用ffpython轻松实现C++嵌入python和扩展pyton

Introduction

ffpython is a C++ lib, which is to simplify tasks that embed Python and extend Python. As the author, I am a developer for MMO server. Mainly I use C++ to implement part that needs to response user's requests in realtime, while other logic part that needs to be modified frequently is implemented by Python. Python makes it possible to reload our part of the server when the server is running. Python is so easy that even my colleague with no programing skills can implement some npc script. When I was first in charge of integrating Python runtime interpreter to our C++ server, I used Boost.python. Somehow Boost.python helped me solve most problems about Python API especially parts of Python reference. But Boost.python is not perfect.ffpython是C ++库，用于简化嵌入Python和扩展Python的任务。作为作者，我是MMO服务器的开发人员。我主要使用C ++实现需要实时响应用户请求的部分，而其他需要经常修改的逻辑部分则由Python实现。使用Python，可以在服务器运行时重新加载服务器的一部分。Python非常简单，即使我没有编程技能的同事也可以实现一些npc脚本。当我第一次负责将Python运行时解释器集成到我们的C ++服务器时，我使用了Boost.python。Boost.python以某种方式帮助我解决了有关Python API的大多数问题，尤其是Python参考的某些部分。但是Boost.python并不完美。

• When exception happens while invoking python function by boost.python, boost.python doesn't provide interface to fetch traceback information.
• Boost python is a big lib to some extent. Someone will find it much difficult who just wants to try to experience how embedding Python works.
• Boost.pyhon supports badly to extend python by using C++ static function and class in runtime. Boost.python recommends to use dynamic library to extending python.
• Someone who wants to learn example code using Python API will find it difficult to understand well boost.python codes, in my opinion.
• If you have the need to convert data between C++ STL container and python object builtin, you have to implement these codes yourself, while Python reference is so annoying.
• 当boost.python调用python函数时发生异常时，boost.python不提供获取回溯信息的接口。
• Boost python在某种程度上是一个很大的库。只是想尝试体验嵌入Python的工作原理的人会发现很难。
• Boost.pyhon static 在运行时使用C ++ 函数和类严重支持扩展python 。Boost.python建议使用动态库来扩展python。
• 我认为，想要使用Python API学习示例代码的人会发现很难很好地理解boost.python代码。
• 如果您需要在C ++ STL容器和内置的python对象之间转换数据，则必须自己实现这些代码，而Python参考非常令人讨厌。

FFPython

Firstly, I implemented it just for converting data between C++ STL container and python object. Some of my colleagues have writes a lot of code using Python API directly. But there is some trap in some Python API even engineers who have a lot of experience using Python may have lost. PyDict_SetItem will auto increase reference key and value arguments, but other Python builtin structure API like PyTuple_SetItem will not increase reference the argument. It will cause memory leak. So I wanted to wrap operations about converting data between C++ STL container and Python builtin structure. Finally, I found some elegant ways to wrap embedding Python and extending Python by C++ template skills. So that is how FFPyhton was born.首先，我实现了它，仅用于在C ++ STL容器和python对象之间转换数据。我的一些同事直接使用Python API编写了很多代码。但是在某些Python API中仍然存在一些陷阱，即使具有丰富使用Python经验的工程师也可能会迷失方向。PyDict_SetItem将自动增加引用键和值参数，但其他Python内置结构API PyTuple_SetItem 不会增加引用参数。它将导致内存泄漏。所以我想包装有关在C ++ STL容器和Python内置结构之间转换数据的操作。最后，我找到了一些优雅的方法来包装嵌入的Python和通过C ++模板技能扩展Python。这就是FFPyhton的诞生方式。

Embedding Python

Sometimes I think it's easier to show codes to readers here. ^_^. But it will be forbidden by administrator if I post lots of code. O(n_n)O~. So see code files or Github.

When Embedding Python, such functions are most needed.

• Fetch global variable of python script(or module). This happens when you use Python script as config files.
• Call python function in script. That is the most useful interface. Two parts of it are important.
  1. It should be supported to use C++ builtin type and C++ STL container as argument.
  2. It should be supported to convert returned value of Python builtin types (like list, tuple, dict, string...) to C++ builtin types.
• Fetch exception information when exception happens, especially traceback information. Because of feature of dynamic type, exception regularly happens even in online server, let alone debugging time. ffpython will throw std exception when Python exception happens. So it is much easier to print or log traceback info by output exception.what() .
• ffpython support nine arguments.
• ffpython implemented by C++ template to wrap Python API. It is easy to understand how it works if you see the code.

• 有时我认为在这里向读者显示代码更容易。^ _ ^。但是如果我发布很多代码，它将被管理员禁止。O（N_N）O〜。因此，请参阅代码文件或Github。

  嵌入Python时，最需要这些功能。

  • 获取python脚本（或模块）的全局变量。当您将Python脚本用作配置文件时，会发生这种情况。
  • 在脚本中调用python函数。那是最有用的界面。它的两个部分很重要。
    1. 应该支持使用C ++内置类型和C ++ STL容器作为参数。
    2. 应该支持将Python内置类型（如list，tuple，dict，string ...）的返回值转换为C ++内置类型。
  • 发生异常时获取异常信息，尤其是回溯信息。由于具有动态类型的功能，即使在联机服务器中也经常发生异常，更不用说调试时间了。当Python发生异常时，ffpython将抛出std异常。因此，通过exception.what()输出打印或记录回溯信息要容易得多。
  • ffpython支持九个参数。
  • 由C ++模板实现的ffpython，用于包装Python API。如果看到代码，很容易理解它是如何工作的。

printf("sys.version=%s\n",
ffpython.get_global_var<string>("sys", "version").c_str());

int a1 = 100; float a2 = 3.14f; string a3 = "OhWell";
ffpython.call<void>("fftest", "test_base", a1, a2, a3);
vector<int> a1;a1.push_back(100);a1.push_back(200);
list<string> a2; a2.push_back("Oh");a2.push_back("Nice");
vector<list<string> > a3;a3.push_back(a2);
ffpython.call<bool>("fftest", "test_stl", a1, a2, a3);
typedef map<string, list<vector<int> > > ret_t;
ret_t val = ffpython.call<ret_t>("fftest", "test_return_stl");

Extending Python

ffpython recommends to register C++ function/class in runtime. It works to design and develop MMO game server. So that is common use for me. There are some key points when embedding Python.

• ffpython supports to register C++ static function. C++ builtin types and STL container can be as arguments.
• C++ class can be registered to Python.

Register C++ static function, all base type supported. Arg num can be nine.ffpython建议在运行时注册C ++函数/类。它致力于设计和开发MMO游戏服务器。所以这对我来说很普遍。嵌入Python时有一些关键点。

• ffpython支持注册C ++ static函数。C ++内置类型和STL容器可以作为参数。
• 可以将C ++类注册到Python。

注册C ++ static 函数，支持所有基本类型。Arg num可以是9。

static int print_val(int a1, float a2, const string& a3, const vector<double>& a4)
{
printf("%s[%d,%f,%s,%d]\n", __FUNCTION__, a1, a2, a3.c_str(), a4.size());
return 0;
}

ffpython_t ffpython;//("ext1");
ffpython.reg(&print_val, "print_val");
ffpython.init("ext1");

Register C++ class, Python can use it just like builtin types.注册C ++类，Python可以像内置类型一样使用它。

class foo_t{

public:
foo_t(int v_):m_value(v_){
printf("%s\n", __FUNCTION__);
}
virtual ~foo_t(){
printf("%s\n", __FUNCTION__);
}
int get_value() const { return m_value; }
void set_value(int v_) { m_value = v_; }
void test_stl(map<string, list<int> >& v_)
{
printf("%s\n", __FUNCTION__);
}
int m_value;
};
class dumy_t: public foo_t
{
public:
dumy_t(int v_):foo_t(v_)
{
printf("%s\n", __FUNCTION__);
}
~dumy_t()
{
printf("%s\n", __FUNCTION__);
}
void dump()
{
printf("%s\n", __FUNCTION__);
}
};
static foo_t* obj_test(dumy_t* p)
{
printf("%s\n", __FUNCTION__);
return p;
}
void test_register_base_class(ffpython_t& ffpython)
{
ffpython.reg_class<foo_t, PYCTOR(int)>("foo_t")
.reg(&foo_t::get_value, "get_value")
.reg(&foo_t::set_value, "set_value")
.reg(&foo_t::test_stl, "test_stl")
.reg_property(&foo_t::m_value, "m_value");
};