用C++实现一个Thmysql类，实现Python标准库PyMysql的基本功能，并提供与PyMysql类似的API，并用pybind11将Thmysql封装为Python库。

PyMysql Thmysql(C++) Thmysql(Python) connect connect connect cursor —— —— execute execute execute fetchone fetchone fetchone fetchall fetchall fetchall close close close

一.开发环境

• Windows64位操作系统；
• mysql 5.5.28 for Win64(x86);
• pycharm 2019.1.1。

二.PyMysql数据库查询

#文件名：python_test.pyimport pymysql# 连接databaseconn = pymysql.connect(host="localhost",user="root",password="123456", database="test",charset="utf8")# 得到一个可以执行SQL语句的光标对象cursor = conn.cursor() # 执行完毕返回的结果集默认以元组显示# 执行SQL语句cursor.execute("use information_schema")cursor.execute("select version();")first_line = cursor.fetchone()print(first_line)cursor.execute("select * from character_sets;")res = cursor.fetchall()print(res)# 关闭光标对象cursor.close()# 关闭数据库连接conn.close()

三.开发步骤

将mysql安装目录下的include和lib文件夹拷到project目录中；

将lib文件夹中的libmysql.dll文件拷到system32路径下；

定义MysqlInfo结构体，实现C++版的Thmysql类；

编写封装函数；

通过setuptools将C++代码编译为Python库。

四.代码实现

// 文件名：thmysql.h#include <Windows.h>#include "mysql.h"#include <iostream>#include <string>#include <vector>#pragma comment(lib, "lib/libmysql.lib")using namespace std;typedef struct MysqlInfo{ string m_host; string m_user; string m_passwd; string m_db; unsigned int m_port; string m_unix_socket; unsigned long m_client_flag; MysqlInfo(){} MysqlInfo(string host, string user, string passwd, string db, unsigned int port, string unix_socket, unsigned long client_flag){ m_host = host; m_user = user; m_passwd = passwd; m_db = db; m_port = port; m_unix_socket = unix_socket; m_client_flag = client_flag; }}MysqlInfo;class Thmysql{ public: Thmysql(); void connect(MysqlInfo&); void execute(string); vector<vector<string>> fetchall(); vector<string> fetchone(); void close(); private: MYSQL mysql; MYSQL_RES * mysql_res; MYSQL_FIELD * mysql_field; MYSQL_ROW mysql_row; int columns; vector<vector<string>> mysql_data; vector<string> first_line;};// 文件名：thmysql.cpp#include <iostream>#include "thmysql.h"Thmysql::Thmysql(){ if(mysql_library_init(0, NULL, NULL) != 0){ cout << "MySQL library initialization failed" << endl; } if(mysql_init(&mysql) == NULL){ cout << "Connection handle initialization failed" << endl; }}void Thmysql::connect(MysqlInfo& msInfo){ string host = msInfo.m_host; string user = msInfo.m_user; string passwd = msInfo.m_passwd; string db = msInfo.m_db; unsigned int port = msInfo.m_port; string unix_socket = msInfo.m_unix_socket; unsigned long client_flag = msInfo.m_client_flag; if(mysql_real_connect(&mysql, host.c_str(), user.c_str(), passwd.c_str(), db.c_str(), port, unix_socket.c_str(), client_flag) == NULL){ cout << "Unable to connect to MySQL" << endl; }}void Thmysql::execute(string sqlcmd){ mysql_query(&mysql, sqlcmd.c_str()); if(mysql_errno(&mysql) != 0){ cout << "error: " << mysql_error(&mysql) << endl; }}vector<vector<string>> Thmysql::fetchall(){ // 获取 sql 指令的执行结果 mysql_res = mysql_use_result(&mysql); // 获取查询到的结果的列数 columns = mysql_num_fields(mysql_res); // 获取所有的列名 mysql_field = mysql_fetch_fields(mysql_res); mysql_data.clear(); while(mysql_row = mysql_fetch_row(mysql_res)){ vector<string> row_data; for(int i = 0; i < columns; i++){ if(mysql_row[i] == nullptr){ row_data.push_back("None"); }else{ row_data.push_back(mysql_row[i]); } } mysql_data.push_back(row_data); } // 没有mysql_free_result会造成内存泄漏：Commands out of sync; you can't run this command now mysql_free_result(mysql_res); return mysql_data;}vector<string> Thmysql::fetchone(){ // 获取 sql 指令的执行结果 mysql_res = mysql_use_result(&mysql); // 获取查询到的结果的列数 columns = mysql_num_fields(mysql_res); // 获取所有的列名 mysql_field = mysql_fetch_fields(mysql_res); first_line.clear(); mysql_row = mysql_fetch_row(mysql_res); for(int i = 0; i < columns; i++){ if(mysql_row[i] == nullptr){ first_line.push_back("None"); }else{ first_line.push_back(mysql_row[i]); } } mysql_free_result(mysql_res); return first_line;}void Thmysql::close(){ mysql_close(&mysql); mysql_library_end();}// 文件名：thmysql_wrapper.cpp#include "pybind11/pybind11.h"#include "pybind11/stl.h"#include "thmysql.h"namespace py = pybind11;PYBIND11_MODULE(thmysql, m){ m.doc() = "C++操作Mysql"; py::class_<MysqlInfo>(m, "MysqlInfo") .def(py::init()) .def(py::init<string, string, string, string, unsigned int, string, unsigned long>(), py::arg("host"), py::arg("user"), py::arg("passwd"), py::arg("db"),py::arg("port"), py::arg("unix_socket") = "NULL", py::arg("client_flag")=0) .def_readwrite("host", &MysqlInfo::m_host) .def_readwrite("user", &MysqlInfo::m_user) .def_readwrite("passwd", &MysqlInfo::m_passwd) .def_readwrite("db", &MysqlInfo::m_db) .def_readwrite("port", &MysqlInfo::m_port) .def_readwrite("unix_socket", &MysqlInfo::m_unix_socket) .def_readwrite("client_flag", &MysqlInfo::m_client_flag); py::class_<Thmysql>(m, "Thmysql") .def(py::init()) .def("connect", &Thmysql::connect) .def("execute", &Thmysql::execute, py::arg("sql_cmd")) .def("fetchall", &Thmysql::fetchall) .def("fetchone", &Thmysql::fetchone) .def("close", &Thmysql::close);}#文件名：setup.pyfrom setuptools import setup, Extensionfunctions_module = Extension( name='thmysql', sources=['thmysql.cpp', 'thmysql_wrapper.cpp'], include_dirs=[r'D:\software\pybind11-master\include', r'D:\software\Anaconda\include', r'D:\project\thmysql\include'],)setup(ext_modules=[functions_module])

五.Thmysql数据库查询

#文件名：test.pyfrom thmysql import Thmysql, MysqlInfoinfo = MysqlInfo("localhost", "root", "123456", "", 3306)conn = Thmysql()# 连接databaseconn.connect(info)# 执行SQL语句conn.execute("use information_schema")conn.execute("select version();")first_line = conn.fetchone()print(first_line)conn.execute("select * from character_sets;")res = conn.fetchall()print(res)# 关闭数据库连接conn.close()

总结

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