##ORM介绍
#对象关系映射
在python中出名的是对象关系映射框架：sqlalchemy
#优点: 能够让不会mysql的程序员也能够顺顺利利的操作数据库 #缺点: 可扩展性比较差 #对象关系映射 类 >>> 数据库的表 对象 >>> 数据库的表的一条记录 对象点属性 >>> 记录的某个字段对应的值
#步骤分析
1、前言：User(dict)----->User类继承了字典dict------>实例化user=User(name='icon')------>user['name']=owen
User类中使用__getattr__和__setattr__方法------->可以实现对象点属性：user.name=icon
2、__getattr__和__setattr__方法区别:
__getattr__:当对未定义的属性名称和实例进行点号时,就会用属性名作为字符串调用这个方法。如果继承树可以找到该属性，则不调用此方法
__setattr__:会拦截所有属性的的赋值语句
3、定义Field：数据库中每一列数据，都有：列名，列的数据类型，是否是主键，默认值
4、定义Model基类：
5、定义ModelMetaclass元类
6、单例模式（四五种类型，后续再把该知识点补上）
##ORM单例模式
from orm_singleton.mysql_singleton import Mysql # 定义字段类 class Field(object): def __init__(self, name, column_type, primary_key, default): self.name = name self.column_type = column_type self.primary_key = primary_key self.default = default # 定义具体的字段 class StringField(Field): def __init__(self, name, column_type='varchar(255)', primary_key=False, default=None): super().__init__(name, column_type, primary_key, default) class IntegerField(Field): def __init__(self, name, column_type='int', primary_key=False, default=None): super().__init__(name, column_type, primary_key, default) class ModelMetaClass(type): def __new__(cls, class_name, class_bases, class_attrs): # 我仅仅只想拦截模型表的类的创建过程 if class_name == 'Models': return type.__new__(cls, class_name, class_bases, class_attrs) # 给类放表名,主键字段,所有字段 table_name = class_attrs.get('table_name', class_name) # 定义一个存储主键的变量 primary_key = None # 定义一个字典用来存储用户自定义的表示表的所有字段信息 mappings = {} # for循环当前类的名称空间 for k, v in class_attrs.items(): if isinstance(v, Field): mappings[k] = v if v.primary_key: if primary_key: raise TypeError("主键只能有一个") primary_key = v.name # 将重复的键值对删除 for k in mappings.keys(): class_attrs.pop(k) if not primary_key: raise TypeError('必须要有一个主键') # 将处理好的数据放入class_attrs中 class_attrs['table_name'] = table_name class_attrs['primary_key'] = primary_key class_attrs['mappings'] = mappings return type.__new__(cls, class_name, class_bases, class_attrs) class Models(dict, metaclass=ModelMetaClass): def __init__(self, **kwargs): super().__init__(**kwargs) “”“ # __getattr__:对象获取自己没有的属性或方法的时候自动触发 # __setattr__:当对象obj.name='jason' 固定句式 ”“” def __getattr__(self, item): return self.get(item, '没有该键值对') def __setattr__(self, key, value): self[key] = value # 查询方法 @classmethod def select(cls, **kwargs): ms = Mysql.singleton() # select * from userinfo if not kwargs: sql = 'select * from %s' % cls.table_name res = ms.select(sql) else: # select * from userinfo where id = 1 k = list(kwargs.keys())[0] v = kwargs.get(k) sql = 'select * from %s where %s=?' % (cls.table_name, k) # select * from userinfo where id = ? sql = sql.replace('?', '%s') # select * from userinfo where id = %s res = ms.select(sql,v) if res: return [ cls(**r) for r in res] # 将数据库的一条数据映射成类的对象 # 新增方法 def save(self): ms = Mysql.singleton() # insert into userinfo(name,password) values('jason','123') # insert into %s(%s) values(?) fields = [] # [name,password] values = [] args = [] for k,v in self.mappings.items(): if not v.primary_key: # 将id字段去除 因为新增一条数据 id是自动递增的不需要你传 fields.append(v.name) args.append('?') values.append(getattr(self,v.name)) # insert into userinfo(name,password) values(?,?) sql = "insert into %s(%s) values(%s)"%(self.table_name,','.join(fields),','.join(args)) # insert into userinfo(name,password) values(?,?) sql = sql.replace('?','%s') ms.execute(sql,values) # 修改方法:基于已经存在了的数据进行一个修改操作 def update(self): ms = Mysql.singleton() # update userinfo set name='jason',password='123' where id = 1 fields = [] # [name,password] values = [] pr = None for k,v in self.mappings.items(): if v.primary_key: pr = getattr(self,v.name,v.default) else: fields.append(v.name+'=?') values.append(getattr(self,v.name,v.default)) sql = 'update %s set %s where %s = %s'%(self.table_name,','.join(fields),self.primary_key,pr) # update userinfo set name='?',password='?' where id = 1 sql = sql.replace('?','%s') ms.execute(sql,values) #测试的话放在main下面，这样当作模块执行时main下面语句不执行 if __name__ == '__main__': class Teacher(Models): table_name = 'teacher' tid = IntegerField(name='tid',primary_key=True) tname = StringField(name='tname') # obj = Teacher(tname='jason老师') # obj.save() # res = Teacher.select() # for r in res: # print(r.tname) # print(res) res = Teacher.select(tid=1) teacher_obj = res[0] teacher_obj.tname = 'jerry老师' teacher_obj.update() # class User(Models): # table_name = 'User' # id = IntegerField(name='id', primary_key=True) # name = StringField(name='name') # password = StringField(name='password') # print(User.primary_key) # print(User.mappings) # obj = User(name='jason') # print(obj.table_name) # print(obj.primary_key) # print(obj.mappings)
import pymysql class Mysql(object): _instance = None def __init__(self): self.conn = pymysql.connect( host = '127.0.0.1', port = 3306, user = 'root', password = '123', database = 'db2', charset = 'utf8', autocommit = True # 自动提交 ) self.cursor = self.conn.cursor(pymysql.cursors.DictCursor) def close(self): self.cursor.close() self.conn.close() def select(self,sql,args=None): self.cursor.execute(sql,args) res = self.cursor.fetchall() # 列表套字典 return res def execute(self,sql,args): try: self.cursor.execute(sql,args) except BaseException as e : print(e) @classmethod def singleton(cls): if not cls._instance: cls._instance = cls() return cls._instance
##ORM数据库连接池
from orm_singleton.mysql_singleton import Mysql # 定义字段类 class Field(object): def __init__(self, name, column_type, primary_key, default): self.name = name self.column_type = column_type self.primary_key = primary_key self.default = default # 定义具体的字段 class StringField(Field): def __init__(self, name, column_type='varchar(255)', primary_key=False, default=None): super().__init__(name, column_type, primary_key, default) class IntegerField(Field): def __init__(self, name, column_type='int', primary_key=False, default=None): super().__init__(name, column_type, primary_key, default) class ModelMetaClass(type): def __new__(cls, class_name, class_bases, class_attrs): # 我仅仅只想拦截模型表的类的创建过程 if class_name == 'Models': return type.__new__(cls, class_name, class_bases, class_attrs) # 给类放表名,主键字段,所有字段 table_name = class_attrs.get('table_name', class_name) # 定义一个存储主键的变量 primary_key = None # 定义一个字典用来存储用户自定义的表示表的所有字段信息 mappings = {} # for循环当前类的名称空间 for k, v in class_attrs.items(): if isinstance(v, Field): mappings[k] = v if v.primary_key: if primary_key: raise TypeError("主键只能有一个") primary_key = v.name # 将重复的键值对删除 for k in mappings.keys(): class_attrs.pop(k) if not primary_key: raise TypeError('必须要有一个主键') # 将处理好的数据放入class_attrs中 class_attrs['table_name'] = table_name class_attrs['primary_key'] = primary_key class_attrs['mappings'] = mappings return type.__new__(cls, class_name, class_bases, class_attrs) class Models(dict, metaclass=ModelMetaClass): def __init__(self, **kwargs): super().__init__(**kwargs) def __getattr__(self, item): return self.get(item, '没有该键值对') def __setattr__(self, key, value): self[key] = value # 查询方法 @classmethod def select(cls, **kwargs): ms = Mysql() # select * from userinfo if not kwargs: sql = 'select * from %s' % cls.table_name res = ms.select(sql) else: # select * from userinfo where id = 1 k = list(kwargs.keys())[0] v = kwargs.get(k) sql = 'select * from %s where %s=?' % (cls.table_name, k) # select * from userinfo where id = ? sql = sql.replace('?', '%s') # select * from userinfo where id = %s res = ms.select(sql,v) if res: return [ cls(**r) for r in res] # 将数据库的一条数据映射成类的对象 # 新增方法 def save(self): ms = Mysql() # insert into userinfo(name,password) values('jason','123') # insert into %s(%s) values(?) fields = [] # [name,password] values = [] args = [] for k,v in self.mappings.items(): if not v.primary_key: # 将id字段去除 因为新增一条数据 id是自动递增的不需要你传 fields.append(v.name) args.append('?') values.append(getattr(self,v.name)) # insert into userinfo(name,password) values(?,?) sql = "insert into %s(%s) values(%s)"%(self.table_name,','.join(fields),','.join(args)) # insert into userinfo(name,password) values(?,?) sql = sql.replace('?','%s') ms.execute(sql,values) # 修改方法:基于已经存在了的数据进行一个修改操作 def update(self): ms = Mysql() # update userinfo set name='jason',password='123' where id = 1 fields = [] # [name,password] values = [] pr = None for k,v in self.mappings.items(): if v.primary_key: pr = getattr(self,v.name,v.default) else: fields.append(v.name+'=?') values.append(getattr(self,v.name,v.default)) sql = 'update %s set %s where %s = %s'%(self.table_name,','.join(fields),self.primary_key,pr) # update userinfo set name='?',password='?' where id = 1 sql = sql.replace('?','%s') ms.execute(sql,values) if __name__ == '__main__': class Teacher(Models): table_name = 'teacher' tid = IntegerField(name='tid',primary_key=True) tname = StringField(name='tname') # obj = Teacher(tname='jason老师') # obj.save() # res = Teacher.select() # for r in res: # print(r.tname) # print(res) res = Teacher.select(tid=1) teacher_obj = res[0] teacher_obj.tname = 'jason老师' teacher_obj.update() res1 = Teacher.select() print(res1) # class User(Models): # table_name = 'User' # id = IntegerField(name='id', primary_key=True) # name = StringField(name='name') # password = StringField(name='password') # print(User.primary_key) # print(User.mappings) # obj = User(name='jason') # print(obj.table_name) # print(obj.primary_key) # print(obj.mappings)
import pymysql from orm_pool import db_pool class Mysql(object): def __init__(self): self.conn = db_pool.POOL.connection() self.cursor = self.conn.cursor(pymysql.cursors.DictCursor) def close(self): self.cursor.close() self.conn.close() def select(self,sql,args=None): self.cursor.execute(sql,args) res = self.cursor.fetchall() # 列表套字典 return res def execute(self,sql,args): try: self.cursor.execute(sql,args) except BaseException as e : print(e)
from DBUtils.PooledDB import PooledDB import pymysql POOL = PooledDB( creator=pymysql, # 使用链接数据库的模块 maxconnections=6, # 连接池允许的最大连接数，0和None表示不限制连接数 mincached=2, # 初始化时，链接池中至少创建的空闲的链接，0表示不创建 maxcached=5, # 链接池中最多闲置的链接，0和None不限制 maxshared=3, # 链接池中最多共享的链接数量，0和None表示全部共享。PS: 无用，因为pymysql和MySQLdb等模块的 threadsafety都为1，所有值无论设置为多少，_maxcached永远为0，所以永远是所有链接都共享。 blocking=True, # 连接池中如果没有可用连接后，是否阻塞等待。True，等待；False，不等待然后报错 maxusage=None, # 一个链接最多被重复使用的次数，None表示无限制 setsession=[], # 开始会话前执行的命令列表。如：["set datestyle to ...", "set time zone ..."] ping=0, # ping MySQL服务端，检查是否服务可用。# 如：0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always host='127.0.0.1', port=3306, user='root', password='123', database='db2', charset='utf8', autocommit='True' )