def __init__():
        pass

lass Baby:
    def __init__(self,name):#構(gòu)造函數(shù)
        self.name = name
    def cry(self):
        self.action = '哭了'
        print(self.action)
feng = Baby('小紅')
print(feng.name)#實(shí)例化時(shí)構(gòu)造函數(shù)自動(dòng)執(zhí)行，
print(feng.action)#cry方法未被執(zhí)行，直接調(diào)用feng.action會(huì)報(bào)錯(cuò)，object has no attribute對(duì)象沒有該屬性

class Baby:
    def __init__(self,name):#構(gòu)造函數(shù)
        self.name = name
    def cry(self):
        self.action = '哭了'
        print(self.action)
feng = Baby('小紅')
feng.cry()#先調(diào)用cry這個(gè)方法
print(feng.action)

class Baby:
    def __init__(self,name):#構(gòu)造函數(shù)
        self.name = name
        self.cry()#將cry這個(gè)方法放在構(gòu)造函數(shù)里
    def cry(self):
        self.action = '哭了'
        print(self.action)
feng = Baby('小紅')
print(feng.action)

 def __del__():
        pass

import pymysql
class MySQL(object):
    def __init__(self,host,user,passwd,db,port=3306,charset='utf8'):#構(gòu)造函數(shù),類實(shí)例化的時(shí)候執(zhí)行
        try:
            self.conn = pymysql.connect(
                host = host,user=user,passwd=passwd,db=db,port=port,charset=charset,
                autocommit=True  # 自動(dòng)提交，執(zhí)行insert，update語句時(shí)，可以自動(dòng)提交
            )
        except Exception as e:
            print('數(shù)據(jù)庫連接失敗，%s'%e)
        else:
            self.cur = self.conn.cursor(cursor=pymysql.cursors.DictCursor)
    def __del__(self):#析構(gòu)函數(shù),實(shí)例被銷毀的時(shí)候執(zhí)行
        self.cur.close()
        self.conn.close()
        print('數(shù)據(jù)庫連接關(guān)閉')
    def ex_sql(self,sql):
        try:
            self.cur.execute(sql)
        except Exception as e:
            print('sql語句錯(cuò)誤，%s'%sql)
        else:
            self.res = self.cur.fetchall()
            return self.res #有沒有返回值都可以
my = MySQL('127.0.0.1', 'root', '123456', 'data')
my.ex_sql('select * from stu')
print(my.res)#可以用實(shí)例屬性取值
# print(my.ex_sql('select * from stu'))#也可以用實(shí)例方法的返回值
print('我是最后一行代碼')#執(zhí)行完最后一行代碼，數(shù)據(jù)庫連接關(guān)閉