day6面向對象--繼承、多態

繼承

    繼承：就像遺傳一樣，繼承就是擁有父類的所有方法和屬性，並且能夠定義自己獨特的屬性和方法，對上面的類進行擴展。

    可以什麼都不寫，直接繼承父類，如下：

class People(object):

    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):
    pass

class Woman(People):
    pass

m1 = Man("chenronghua",16)
m1.eat()
運行結果如下：
chenronghua is eating......

    上面代碼可以看出，首先定義了一個People的類，還有一個Man(People)類直接繼承People類。

    下麵，我們在上面的Man()類中定義一個單獨的方法，如下：

class People(object):

    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):
    def piao(self):
        print("%s is piaoing......20s......" %self.name)

class Woman(People):
    pass

m1 = Man("chenronghua",16)
m1.piao()
運行結果如下：
chenronghua is piaoing......20s......

    上面，我們給Man()增加了新的方法，可以看出，能夠執行。

    下麵，我們來重寫父類。擴展新功能，子類並且要具有父類的所有方法與屬性。在子類中調用父類：

class People(object):

    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):
    def piao(self):
        print("%s is piaoing......20s......" %self.name)

    def sleep(self):
        People.sleep(self)
        print("man is sleeping......")

class Woman(People):
    pass

m1 = Man("chenronghua",16)
m1.sleep()

    上面代碼中，子類調用了父類中的方法，要明白本質，創建實例的本質是增加了一個新的記憶體變數。

    不同類中方法的調用：

class People(object):

    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):
    def piao(self):
        print("%s is piaoing......20s......" %self.name)

    def sleep(self):
        People.sleep(self)
        print("man is sleeping......")

class Woman(People):

    def get_birth(self):
        print("%s is borning a bady......" %self.name)

# m1 = Man("chenronghua",16)
# m1.sleep()

w1 = Woman("chenronghua",26)
w1.get_birth()
w1.piao()
運行如下：
chenronghua is borning a bady......
Traceback (most recent call last):
  File "/home/zhuzhu/第六天/inherit.py", line 34, in <module>
    w1.piao()
AttributeError: 'Woman' object has no attribute 'piao'

    從上面可以看出，繼承同一個父類的子類是方法是不能相互調用的。

class People(object):

    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):
    def __init__(self,name,age,money):     #給男的單獨增加屬性
        People.__init__(self,name,age)
        self.money = money
        print("%s 剛出生就有%s元" %(self.name,self.money))    #構造函數的時候就會執行代碼


    def piao(self):
        print("%s is piaoing......20s......" %self.name)

    def sleep(self):
        People.sleep(self)
        print("man is sleeping......")

class Woman(People):

    def get_birth(self):
        print("%s is borning a bady......" %self.name)

m1 = Man("chenronghua",16,100)
m1.sleep()
運行結果如下：
chenronghua 剛出生就有100元
chenronghua is sleeping.....
man is sleeping.....

    從上面代碼可以看出，__init__(self,name,age,money)類的初始化，People.__init__(self,name,age)繼承，繼承父類的屬性，普通的繼承。

    下麵來看看新式類中的繼承。

class People(object):

    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):
    def __init__(self,name,age,money):     #給男的單獨增加屬性
        super(Man,self).__init__(name,age)
        self.money = money
        print("%s 剛出生就有%s元" %(self.name,self.money))    #構造函數的時候就會執行代碼


    def piao(self):
        print("%s is piaoing......20s......" %self.name)

    def sleep(self):
        People.sleep(self)
        print("man is sleeping......")

class Woman(People):

    def get_birth(self):
        print("%s is borning a bady......" %self.name)

m1 = Man("chenronghua",16,100)
m1.sleep()

    新式類是用super()函數來實現繼承的，super(Man,self).__init__(name,age)實現繼承，新式類和舊式類的差別主要體現在多繼承上面。

    下麵看下類的多繼承問題：

class People(object):

    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 Relation(object):

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

class Man(People,Relation):
    def __init__(self,name,age,money):     #給男的單獨增加屬性
        super(Man,self).__init__(name,age)    #超級父類，Man繼承父類name,age
        self.money = money
        print("%s 剛出生就有%s元" %(self.name,self.money))    #構造函數的時候就會執行代碼


    def piao(self):
        print("%s is piaoing......20s......" %self.name)

    def sleep(self):
        People.sleep(self)
        print("man is sleeping......")

class Woman(People,Relation):

    def get_birth(self):
        print("%s is borning a bady......" %self.name)

w1 = Woman("ruhua",18)

m1 = Man("chenronghua",16,100)
m1.make_friends(w1)           #把w1實例當做參數傳給make_friends，等價於obj》w1，obj.name》w1.name

    上面代碼中，當子類繼承多個父類的時候，即便其中一個父類沒有實例化，也能調用另外一個父類的方法和屬性。通過子類把兩個父類關聯到一起。

    多態

    一個介面，多個重用