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Python3.5面向?qū)ο蟪绦蛟O(shè)計之類的繼承和多態(tài)詳解

更新時間：2019年04月24日 11:01:23 作者：loveliuzz

這篇文章主要介紹了Python3.5面向?qū)ο蟪绦蛟O(shè)計之類的繼承和多態(tài),結(jié)合實例形式詳細分析了Python3.5面向?qū)ο蟪绦蛟O(shè)計中類的繼承與多態(tài)常見用法及相關(guān)注意事項,需要的朋友可以參考下

本文實例講述了Python3.5面向?qū)ο蟪绦蛟O(shè)計之類的繼承和多態(tài)。分享給大家供大家參考，具體如下：

1、繼承的定義

繼承是指：可以使用現(xiàn)有類的所有功能，并在無需重新編寫原來的類的情況下對這些功能進行擴展。
（1）通過繼承創(chuàng)建的新類稱為“子類”或“派生類”。
（2）被繼承的類稱為“基類”、“父類”或“超類”。
繼承的過程，就是從一般到特殊的過程。要實現(xiàn)繼承，可以通過“繼承”（Inheritance）和“組合”（Composition）來實現(xiàn)。
在某些 OOP 語言中，一個子類可以繼承多個基類。但是一般情況下，一個子類只能有一個基類，要實現(xiàn)多重繼承，可以通過多級繼承來實現(xiàn)。

2、繼承的分類

繼承概念的實現(xiàn)方式主要有2類：實現(xiàn)繼承、接口繼承。

（1）實現(xiàn)繼承是指使用基類的屬性和方法而無需額外編碼的能力；
（2）接口繼承是指僅使用屬性和方法的名稱、但是子類必須提供實現(xiàn)的能力(子類重構(gòu)父類方法)；
在考慮使用繼承時，有一點需要注意，那就是兩個類之間的關(guān)系應(yīng)該是“屬于”關(guān)系。
抽象類僅定義將由子類創(chuàng)建的一般屬性和方法。
OO開發(fā)范式大致為：劃分對象→抽象類→將類組織成為層次化結(jié)構(gòu)(繼承和合成) →用類與實例進行設(shè)計和實現(xiàn)幾個階段。

3、示例代碼

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

#類的繼承
class People:
 def __init__(self,name,age):
  self.name = name
  self.age = age

 def eat(self):
  print("%s is eating..." %self.name)

 def sleep(self):
  print("%s is sleeping..." %self.name)

 def talk(self):
  print("%s is talking..." %self.name)

class Man(People):  #繼承父類People類
 def make_money(self):
  print("%s is making money..." %self.name)

 def sleep(self):
  People.sleep(self)  #對父類方法的擴展
  print("man is sleeping...")

class Women(People):
 def shop(self):
  print("%s is shopping..." %self.name)

m1 = Man("Jack","20")
m1.eat()
m1.make_money()
m1.sleep()

w1 = Women("Amy","25")
w1.talk()
w1.shop()

運行結(jié)果：

Jack is eating...
Jack is making money...
Jack is sleeping...
man is sleeping...
Amy is talking...
Amy is shopping...

4、子類中對父類的構(gòu)造函數(shù)進行重構(gòu)兩種方法

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

#類的繼承
#class People:  #經(jīng)典類
class People(object):  #新式類
 def __init__(self,name,age):
  self.name = name
  self.age = age

 def eat(self):
  print("%s is eating..." %self.name)

 def sleep(self):
  print("%s is sleeping..." %self.name)

 def talk(self):
  print("%s is talking..." %self.name)

class Man(People):  #繼承父類People類
 def __init__(self,name,age,money):
  #People.__init__(self,name,age)  #(方法一)對構(gòu)造函數(shù)進行重構(gòu)、添加父類中沒有的屬性
  super(Man,self).__init__(name,age) #(方法二)利用super對構(gòu)造函數(shù)進行重構(gòu)（新式類寫法）
  self.money = money
  print("%s have money %s$" %(self.name,self.money))

 def make_money(self):
  print("%s is making money..." %self.name)

 def sleep(self):
  People.sleep(self)  #對父類方法的擴展
  print("man is sleeping...")

class Women(People):
 def shop(self):
  print("%s is shopping..." %self.name)

m1 = Man("Jack","20",10)
m1.eat()
m1.make_money()
m1.sleep()

w1 = Women("Amy","25")
w1.talk()
w1.shop()

運行結(jié)果：

J ack have money 10$
Jack is eating...
Jack is making money...
Jack is sleeping...
man is sleeping...
Amy is talking...
Amy is shopping...

5、多繼承方式

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

#類的繼承
#class People:  #經(jīng)典類
class People(object):  #新式類
 def __init__(self,name,age):
  self.name = name
  self.age = age
  self.friends = []

 def eat(self):
  print("%s is eating..." %self.name)

 def sleep(self):
  print("%s is sleeping..." %self.name)

 def talk(self):
  print("%s is talking..." %self.name)

class Relationship(object):
 def make_friends(self,obj):
  print("%s is making friends with %s" %(self.name,obj.name))
  self.friends.append(obj)

class Man(People,Relationship):  #多繼承
 def __init__(self,name,age,money):
  #People.__init__(self,name,age)  #(方法一)對構(gòu)造函數(shù)進行重構(gòu)、添加父類中沒有的屬性
  super(Man,self).__init__(name,age) #(方法二)利用super對構(gòu)造函數(shù)進行重構(gòu)（新式類寫法）
  self.money = money
  print("%s have money %s$" %(self.name,self.money))

 def make_money(self):
  print("%s is making money..." %self.name)

 def sleep(self):
  People.sleep(self)  #對父類方法的擴展
  print("man is sleeping...")

class Women(People,Relationship): #多繼承
 def shop(self):
  print("%s is shopping..." %self.name)

m1 = Man("Jack","20",10)

w1 = Women("Amy","25")

m1.make_friends(w1)
w1.name = "liu"
print(m1.friends)

運行結(jié)果：

Jack have money 10$
Jack is making friends with Amy
[<__main__.Women object at 0x0057FA30>]

6、新式類與經(jīng)典類的繼承順序

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

class A(object):		#新式類
 def __init__(self):
  print("A")

class B(A):
 def __init__(self):
  
  print("B")

class C(A):
 def __init__(self):
  print("C")

class D(B,C):
 def __init__(self):
  pass
  #print("D")

obj = D()

7、繼承示例——學(xué)校、教師與學(xué)生

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

#繼承實例(新式類)——模擬學(xué)校、教師與學(xué)生

class School(object):
 def __init__(self,name,addr):
  self.name = name
  self.addr = addr
  self.students = []
  self.stuffs = []

 def enroll(self,stu_obj):  #學(xué)生注冊
  print("%s 學(xué)員辦理注冊" %stu_obj.name)
  self.students.append(stu_obj)

 def heir(self,staff_obj):  #聘請教師
  print("聘請教師 %s" %staff_obj.name)
  self.stuffs.append(staff_obj)

class SchoolMember(object):
 def __init__(self,name,age,sex):
  self.name = name
  self.age = age
  self.sex = sex

 def tell(self):
  pass

class Teacher(SchoolMember):
 def __init__(self,name,age,sex,salary,course):
  super(Teacher,self).__init__(name,age,sex)
  self.salary = salary
  self.course = course

 def tell(self):
  print('''
  ----- info of Teacher:%s -----
  Name:%s
  Age:%s
  Sex:%s
  Salary:%s
  Course:%s
  '''%(self.name,self.name,self.age,self.sex,self.salary,self.course))

 def teach(self):
  print("%s is teaching course [%s]" %(self.name,self.course))

class Student(SchoolMember):
 def __init__(self,name,age,sex,stu_id,grade):
  super(Student,self).__init__(name,age,sex)
  self.stu_id = stu_id
  self.grade = grade

 def tell(self):
  print('''
  ----- info of Student:%s -----
  Name:%s
  Age:%s
  Sex:%s
  Stu_id:%s
  Grade:%s
  '''%(self.name,self.name,self.age,self.sex,self.stu_id,self.grade))

 def pay_tuition(self,amount):
  print("%s has paied tuition for $%s" %(self.name,amount))

#實例化
school = School("qinghua","beijing")

t1 = Teacher("Jack","30","M","20000","Python")
t2 = Teacher("Amy","28","F","15000","Linux")

s1 = Student("liu","23","M","1701","Python")
s2 = Student("wang","25","F","1702","Linux")

#調(diào)用顯示學(xué)生與教師的信息
t1.tell()
s1.tell()

school.heir(t1)  #聘請教師t1
school.enroll(s1) #學(xué)生s1注冊
school.enroll(s2)

print(school.stuffs)
print(school.students)

#聘請的第一位教師教課
school.stuffs[0].teach()
for stu in school.students:
 stu.pay_tuition(5000)

運行結(jié)果：

        ----- info of Teacher:Jack -----
        Name:Jack
        Age:30
        Sex:M
        Salary:20000
        Course:Python


        ----- info of Student:liu -----
        Name:liu
        Age:23
        Sex:M
        Stu_id:1701
        Grade:Python

聘請教師 Jack
liu 學(xué)員辦理注冊
wang 學(xué)員辦理注冊
[<__main__.Teacher object at 0x0059FDB0>]
[<__main__.Student object at 0x0059FDF0>, <__main__.Student object at 0x0059FE10>]
Jack is teaching course [Python]
liu has paied tuition for $5000
wang has paied tuition for $5000

8、多態(tài)（polymorphisn）——一種接口，多種形態(tài)

（1）定義

多態(tài)性（polymorphisn）是允許你將父對象設(shè)置成為和一個或更多的他的子對象相等的技術(shù)，

賦值之后，父對象就可以根據(jù)當(dāng)前賦值給它的子對象的特性以不同的方式運作。

簡單的說，就是一句話：允許將子類類型的指針賦值給父類類型的指針。

多態(tài)的作用：我們知道，封裝可以隱藏實現(xiàn)細節(jié)，使得代碼模塊化；繼承可以擴展已存在的代碼模塊（類）；它們的目的都是為了——代碼重用。

而多態(tài)則是為了實現(xiàn)另一個目的——接口重用！多態(tài)的作用，就是為了類在繼承和派生的時候，保證使用“家譜”中任一類的實例的某一屬性時的正確調(diào)用。

Pyhon 很多語法都是支持多態(tài)的，比如 len(),sorted(), 你給len傳字符串就返回字符串的長度，傳列表就返回列表長度。

（2）示例代碼：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:ZhengzhengLiu

class Animal(object):
 def __init__(self,name):
  self.name = name

 def talk(self):
  raise NotImplementedError("Subclass must implement abstract method")

 # 多態(tài)——一種接口，多種形態(tài)
 @staticmethod
 def animal_talk(obj):
  obj.talk()

class Cat(Animal):
 def talk(self):
  print("%s Meow!" %self.name)

class Dog(Animal):
 def talk(self):
  print("%s Woof! Woof!" % self.name)

d = Dog("A")
#d.talk()

c = Cat("B")
#c.talk()

#多態(tài)
Animal.animal_talk(d)
Animal.animal_talk(c)

運行結(jié)果：