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137 lines
3.9 KiB
Markdown
137 lines
3.9 KiB
Markdown
---
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title: Python3调用c/cpp的方法
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keywords: python, c, cpp,
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desc: python调用so
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date: 2022-03-31
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tags: python, c, cpp
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---
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<!-- more -->
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原文链接：https://blog.csdn.net/springlustre/article/details/101177282
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作者：[springlustre](https://blog.csdn.net/springlustre?type=blog)
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有改动，仅供参考
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python中使用 ctypes 模块可以在python中直接调用C/C++。
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首先要将C/C++编译成动态库（.so)，然后python中调用即可。
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特别注意在调用C++函数需要在函数声明时，加入前缀 extern "C" ，这是因为C++支持函数重载功能，在编译时会改变函数名。在函数声明时，前缀extern "C"可以确保按C的方式进行编译。
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值得注意的是，一定要有函数输入输出类型的声明，int型不用转换，float和double类型需要进行转换；
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ctypes中的变量类型与C中对应如下：
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| ctypes数据类型 | C数据类型 |
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| -------------- | ------------- |
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| c_char | char |
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| c_short | short |
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| c_int | int |
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| c_long | long |
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| c_float | float |
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| c_double | double |
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| c_void_p | void |
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| c_uint8 | unsigned char |
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使用方法：
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- 编写c++代码
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```cpp
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#include <iostream>
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#include <string>
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#include <cstdlib>
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#include <vector>
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#include <stdio.h>
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class Test{
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private:
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double _calculate(int a, double b);
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public:
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double calculate(int a, double b, char c[], int * d, double * e, char ** f);
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};
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double Test::_calculate(int a, double b){
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double res = a+b;
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std::cout<<"res: "<<res<<std::endl;
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return res;
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}
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double Test::calculate(int a, double b, char c[], int * d, double * e, char ** f){
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std::cout<<"a: "<<a<<std::endl;
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std::cout<<"b: "<<b<<std::endl;
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std::cout<<"c: "<<c<<std::endl;
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std::cout<<"d: "<<d[0]<<d[1]<<std::endl;
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std::cout<<"e: "<<e[0]<<e[1]<<std::endl;
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std::cout<<"f: "<<f[0]<<f[1]<<std::endl;
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return this->_calculate(a, b);
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}
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// 封装C接口
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extern "C"{
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// 创建对象
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Test* test_new(){
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return new Test;
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}
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double my_calculate(Test* t, int a, double b, char c[], int * d, double * e, char ** f){
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return t->calculate(a, b,c,d,e,f);
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}
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}
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```
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- 将上面的代码编译成so文件
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> g++ -shared -Wl,-soname,test -o test.so -fPIC test.cpp
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- 使用python调用so文件
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```python
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# -*- coding: utf-8 -*-
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import ctypes
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# 指定动态链接库
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lib = ctypes.cdll.LoadLibrary('./test.so')
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#需要指定返回值的类型，默认是int
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lib.my_calculate.restype = ctypes.c_double
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class Test(object):
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def __init__(self):
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# 动态链接对象
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self.obj = lib.test_new()
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def calculate(self, a, b,c,d,e,f):
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res = lib.my_calculate(self.obj, a, b,c,d,e,f)
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return res
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#将python类型转换成c类型，支持int, float,string的变量和数组的转换
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def convert_type(input):
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ctypes_map = {int:ctypes.c_int,
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float:ctypes.c_double,
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str:ctypes.c_char_p
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}
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input_type = type(input)
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if input_type is list:
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length = len(input)
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if length==0:
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print("convert type failed...input is "+input)
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return null
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else:
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arr = (ctypes_map[type(input[0])] * length)()
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for i in range(length):
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arr[i] = bytes(input[i],encoding="utf-8") if (type(input[0]) is str) else input[i]
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return arr
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else:
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if input_type in ctypes_map:
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return ctypes_map[input_type](bytes(input,encoding="utf-8") if type(input) is str else input)
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else:
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print("convert type failed...input is "+input)
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return null
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if __name__ == '__main__':
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t = Test()
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A1 = 123;
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A2 = 0.789;
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A3 = "C789";
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A4 = [456,789];
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A5 = [0.123,0.456];
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A6 = ["A123", "B456"];
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print(t.calculate(convert_type(A1), convert_type(A2), convert_type(A3),convert_type(A4),convert_type(A5),convert_type(A6)))
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``` |