python调用C++ —— ctypes库尝试

Tech , Comments

python调用c++有很多种方法，今天我就来整理使用一下python中ctypes模块的用法。

网上可以找到很多关于ctypes的使用资料，但都不全：
1.类型介绍不完整
2.只有python传入c++参数
3.只有python接收c++返回
我就针对以上的问题，作一个比较全面的使用介绍吧。

使用很简单，各种拼拼凑凑，看代码就可以懂，就不多说了。

c++ 代码
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#include <iostream>
#include <string>
using namespace std;

typedef struct StructTest
{
    char* name;
    int age;
    int score[3];
}StructTest, *StructPtr;

class TestLib
{
    public:
        int passInt(int a);
        double passDouble(double d);
        char passChar(char c);
        char* passString(char* s);
        StructTest passStruct(StructTest st);
        StructPtr passStructPtr(StructPtr p);
        StructPtr passStructArray(StructTest vst[], int size);
};

int TestLib::passInt(int a) {
    cout << a << " in c++" << endl;
    return a;
}

double TestLib::passDouble(double d) {
    cout << d << " in c++" << endl;
    return d;
}

char TestLib::passChar(char c) {
    cout << c << " in c++" << endl;
    return c;
}

char* TestLib::passString(char* s) {
    cout << s << " in c++" << endl;
    return s;
}

StructTest TestLib::passStruct(StructTest st) {
    cout << st.name << " " << st.age << " " << st.score[2] << " in c++" << endl;
    return st;
}

StructPtr TestLib::passStructPtr(StructPtr p) {
    cout << p->name << " " << p->age << " " << p->score[2] << " in c++" << endl;
    return p;
}

StructPtr TestLib::passStructArray(StructTest vst[], int size) {
    cout << vst[0].name << " in c++" << endl;
    cout << vst[1].name << " in c++" << endl;
    return &vst[0];
}

extern "C" {
    TestLib obj;

    int passInt(int a) {
        return obj.passInt(a);
    }

    double passDouble(double d){
        return obj.passDouble(d);
    }

    char passChar(char c) {
        return obj.passChar(c);
    }

    char* passString(char* s){
        return obj.passString(s);
    }

    StructTest passStruct(StructTest st){
        return obj.passStruct(st);
    }

    StructPtr passStructPtr(StructPtr p){
        return obj.passStructPtr(p);
    }

    StructPtr passStructArray(StructTest vst[], int size){
        return obj.passStructArray(vst, size);
    }
}
// generate it into lib
// g++ -o libTest.so -shared -fPIC cppLib.cpp
python 调用代码
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__author__ = 'xidui'
import ctypes
so = ctypes.cdll.LoadLibrary
lib = so('./libTest.so')

# passInt
print('passInt')
print(lib.passInt(100))
print('--------------------')

# passDouble
print('passDouble')
lib.passDouble.restype = ctypes.c_double
print(str(lib.passDouble(ctypes.c_double(1.23))) + ' in python')
print('--------------------')

# passChar
print('passChar')
lib.passChar.restype = ctypes.c_char
print(str(lib.passChar(ctypes.c_char(65))) + ' in python') # 'A'
print(str(lib.passChar(ctypes.c_char(b'A'))) + ' in python') # 'A'
print('--------------------')

# passString
print('passString')
lib.passString.restype = ctypes.c_char_p
print(str(lib.passString(ctypes.c_char_p(b'abcde'))) + ' in python') # 这里一定要加b
print('--------------------')

# passStruct
print('passStruct')
class Struct(ctypes.Structure):
    _fields_ = [('name', ctypes.c_char_p),
                ('age', ctypes.c_int),
                ('score', ctypes.c_int * 3)]
lib.passStruct.restype = Struct
array = [1, 2, 3]
st = lib.passStruct(Struct(b'xidui', 10, (ctypes.c_int * 3)(*array)))
# p = lib.passStruct(Struct(b'xidui', 10, (ctypes.c_int * 3)(1, 2, 3)))
print(str(st.name) + ' ' + str(st.age) + ' ' + str(st.score[2]) + ' in python')
print('--------------------')

# passStructPointer
print('passStructPointer')
lib.passStructPtr.restype = ctypes.POINTER(Struct)
lib.passStructPtr.argtypes = [ctypes.POINTER(Struct)] # 这行不加，程序会宕
p = lib.passStructPtr(Struct(b'xidui', 10, (ctypes.c_int * 3)(*array)))
print(str(p.contents.name) + ' ' + str(p.contents.age) + ' ' + str(p.contents.score[2]) + ' in python')
print('--------------------')

# passStructArray
print('passStructArray')
lib.passStructArray.restype = ctypes.POINTER(Struct)
lib.passStructArray.argtypes = [ctypes.ARRAY(Struct, 2), ctypes.c_int]
array = [Struct(b'xidui1', 10, (ctypes.c_int * 3)(1, 2, 3)),
    Struct(b'xidui2', 10, (ctypes.c_int * 3)(1, 2, 3))]
p = lib.passStructArray(ctypes.ARRAY(Struct, 2)(*array), 2)
print(str(p.contents.name) + ' ' + str(p.contents.age) + ' ' + str(p.contents.score[2]) + ' in python')
print('--------------------')

大家想要别的类型，可以在留言板中添加，我会尽快更新到博客中

xiduiSoftware Engineer

个人简介。