C++实现PyMysql的基本功能实例详解

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.py
import pymysql
# 连接database
conn = 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()

C++实现PyMysql的基本功能实例详解

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.py
from setuptools import setup, Extension
functions_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.py
from thmysql import Thmysql, MysqlInfo
info = MysqlInfo("localhost", "root", "123456", "", 3306)
conn = Thmysql()
# 连接database
conn.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()

C++实现PyMysql的基本功能实例详解

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原文链接：https://segmentfault.com/a/1190000021875615