面向对象-属性查找与绑定方法

#!/usr/bin/env python # -*- coding:utf-8 -*- # Author: vita class Student: school = 'my_school' def __init__(self,name,sex,age): self.name=name self.sex=sex self.age=age def learn(self): #函数属性 print('is learning') def eat(self): #函数属性 print('is eating') def sleep(self): print('is sleeping') #"1.类中的数据属性是所有对象共享的，id都一样" s1=Student("vita",'女',27) s2=Student("超超",'男',29) print("id(Student.school)",id(Student.school)) print("id(s1.school)",id(s1.school)) print("id(s2.school)",id(s2.school)) #"类的函数是绑定给对象用的，称为绑定到对象的方法，内存地址都不一样" print("Student.learn",Student.learn) print("s1.learn",s1.learn) print("s2.learn",s2.learn) E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py id(Student.school) 1427361290736 id(s1.school) 1427361290736 id(s2.school) 1427361290736 Student.learn <function Student.learn at 0x0000014C555D1D90> s1.learn <bound method Student.learn of <__main__.Student object at 0x0000014C555D85C0>> s2.learn <bound method Student.learn of <__main__.Student object at 0x0000014C555D87F0>> Process finished with exit code 0 #对于school变量，会先到s1.__dict__中查找，即先到自己的名称空间中查找 # 找不到，去类中查找 # 类中找不到，去父类中查找，直到找到顶级父类，找不到，抛出异常 #并不会到类的外面查找

"验证变量首先到对象空间中找，然后到类中找，再到父类中找" "1.先从对象空间中查找，即s1.__dict__中" #!/usr/bin/env python # -*- coding:utf-8 -*- # Author: vita school = 'my_school from out' class Student: def __init__(self,name,sex,age): self.name=name self.sex=sex self.age=age s1=Student("vita",'女',27) s2=Student("超超",'男',29) s1.school="my_school from s1" print(s1.__dict__) print(s1.school) E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py {'name': 'vita', 'sex': '女', 'age': 27, 'school': 'my_school from s1'} my_school from s1 Process finished with exit code 0 "2.再从类中找" #!/usr/bin/env python # -*- coding:utf-8 -*- # Author: vita school = 'my_school from out' class Student: def __init__(self,name,sex,age): self.name=name self.sex=sex self.age=age s1=Student("vita",'女',27) s2=Student("超超",'男',29) Student.school="my_school from class" print(s1.__dict__) print(s1.school) E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py {'name': 'vita', 'sex': '女', 'age': 27} my_school from class Process finished with exit code 0 "3.再从父类中找，稍后讲继承后，再看" "4.类中没有，不会到类外找" #!/usr/bin/env python # -*- coding:utf-8 -*- # Author: vita school = 'my_school from out' class Student: def __init__(self,name,sex,age): self.name=name self.sex=sex self.age=age s1=Student("vita",'女',27) s2=Student("超超",'男',29) print(s1.__dict__) print(s1.school) E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py Traceback (most recent call last): {'name': 'vita', 'sex': '女', 'age': 27} File "E:/PythonProject/python-test/BasicGrammer/test.py", line 15, in <module> print(s1.school) AttributeError: 'Student' object has no attribute 'school' Process finished with exit code 1

#list类型是类list >>> list <class 'list'> >>> set <class 'set'> >>> dict <class 'dict'> >>> str <class 'str'> #实例化三个对象 >>> l1=list() >>> l2=list() >>> l3=list() #三个对象都有绑定方法append,是相同的功能，但内存地址不同 >>> l1.append <built-in method append of list object at 0x0000027FEE617408> >>> l2.append <built-in method append of list object at 0x0000027FEE617448> >>> l3.append <built-in method append of list object at 0x0000027FEE617488> #操作绑定方法l1.append(3)就是往l1添加3,不会影响l2和l3 >>> l1.append(3) >>> l1 [3] >>> l2 [] >>> l3 [] #调用类list.append(l3,111)等同于l3.append(111) >>> list.append(l3,111) >>> l3 [111]

"1.在没有学习类概念时，数据与功能是分离的" def exc1(host,port,db,charset): conn=connect(host,port,db,charset) conn.execute(sql) return xxx def exc2(host,port,db,charset,proc_name) conn=connect(host,port,db,charset) conn.call_proc(sql) return xxx #每次调用都需要重复传入一堆参数 exc1('127.0.0.1',3306,'db1','utf8','select * from tb1;') exc2('127.0.0.1',3306,'db1','utf8','存储过程的名字')

"2.我们后面用到一个解决办法，即全局变量" HOST=‘127.0.0.1’ PORT=3306 DB=‘db1’ CHARSET=‘utf8’ def exc1(host,port,db,charset): conn=connect(host,port,db,charset) conn.execute(sql) return xxx def exc2(host,port,db,charset,proc_name) conn=connect(host,port,db,charset) conn.call_proc(sql) return xxx exc1(HOST,PORT,DB,CHARSET,'select * from tb1;') exc2(HOST,PORT,DB,CHARSET,'存储过程的名字')

"3.学到类之后，是这样的将数据与专门操作该数据的功能整合到一起 " class MySQLHandler: def __init__(self,host,port,db,charset='utf8'): self.host=host self.port=port self.db=db self.charset=charset self.conn=connect(self.host,self.port,self.db,self.charset) def exc1(self,sql): return self.conn.execute(sql) def exc2(self,sql): return self.conn.call_proc(sql) obj=MySQLHandler('127.0.0.1',3306,'db1') obj.exc1('select * from tb1;') obj.exc2('存储过程的名字')

"定义类并产生三个对象" class Chinese: def __init__(self,name,age,sex): self.name=name self.age=age self.sex=sex p1=Chinese('egon',18,'male') p2=Chinese('alex',38,'female') p3=Chinese('wpq',48,'female')

"如果我们新增一个类属性，将会反映给所有对象，而对象却无需修改，直接使用新增的属性即可" class Chinese: country='China' def __init__(self,name,age,sex): self.name=name self.age=age self.sex=sex def tell_info(self): info=''' 国籍:%s 姓名:%s 年龄:%s 性别:%s ''' %(self.country,self.name,self.age,self.sex) print(info) p1=Chinese('egon',18,'male') p2=Chinese('alex',38,'female') p3=Chinese('wpq',48,'female') print(p1.country) p1.tell_info()

1.属性查找

2.绑定方法

3.类即类型

4.面向对象优点小节

4.1优点1：将数据与操作数据的功能整合到一起

4.2优点2：可扩展性高

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