本文和大家分享的主要是python開發(fā)中super()和__init__()的區(qū)別，希望通過本文的分享，對初學(xué)者學(xué)習(xí)這部分內(nèi)容有所幫助。

1、單繼承時super()和__init__()實(shí)現(xiàn)的功能是類似的

class Base(object):

    def __init__(self):

        print 'Base create'

 class childA(Base):

    def __init__(self):

        print 'creat A ',

        Base.__init__(self)

 

 class childB(Base):

    def __init__(self):

        print 'creat B ',

        super(childB, self).__init__()

 

base = Base()

 

a = childA()

b = childB()

輸出結(jié)果：

Basecreate

creat A  Basecreate

creat B  Basecreate

使用super()繼承時不用顯式引用基類。

 

2、super()只能用于新式類中

把基類改為舊式類，即不繼承任何基類

class Base():

    def __init__(self):

        print 'Base create'

執(zhí)行時，在初始化b時就會報錯：

super(childB, self).__init__()TypeError: mustbetype, not classobj

 

3、super不是父類，而是繼承順序的下一個類

在多重繼承時會涉及繼承順序，super（）相當(dāng)于返回繼承順序的下一個類，而不是父類，類似于這樣的功能：

defsuper(class_name, self):

    mro = self.__class__.mro()

    return mro[mro.index(class_name) + 1]

mro()用來獲得類的繼承順序。

例如：

class Base(object):

    def__init__(self):

        print 'Base create'

 class childA(Base):

    def__init__(self):

        print 'enter A '

        # Base.__init__(self)

        super(childA, self).__init__()

        print 'leave A'

 

 class childB(Base):

    def__init__(self):

        print 'enter B '

        # Base.__init__(self)

        super(childB, self).__init__()

        print 'leave B'

 class childC(childA, childB):

    pass

 

c = childC()print c.__class__.__mro__

 

輸入結(jié)果如下：

enter A

enter B

Basecreate

leave B

leave A

(<class '__main__.childC'>, <class '__main__.childA'>, <class '__main__.childB'>, <class '__main__.Base'>, <type 'object'>)

supder和父類沒有關(guān)聯(lián)，因此執(zhí)行順序是A —> B—>—>Base

執(zhí)行過程相當(dāng)于：初始化childC()時，先會去調(diào)用childA的構(gòu)造方法中的 super(childA, self).__init__()， super(childA, self)返回當(dāng)前類的繼承順序中childA后的一個類childB；然后再執(zhí)行childB().__init()__,這樣順序執(zhí)行下去。

在多重繼承里，如果把childA()中的 super(childA, self).__init__() 換成Base.__init__(self)，在執(zhí)行時，繼承childA后就會直接跳到Base類里，而略過了childB：

enter A

Basecreate

leave A

(<class '__main__.childC'>, <class '__main__.childA'>, <class '__main__.childB'>, <class '__main__.Base'>, <type 'object'>)

從super()方法可以看出，super（）的第一個參數(shù)可以是繼承鏈中任意一個類的名字，

如果是本身就會依次繼承下一個類；

如果是繼承鏈里之前的類便會無限遞歸下去；

如果是繼承鏈里之后的類便會忽略繼承鏈匯總本身和傳入類之間的類；

比如將childA()中的super改為：super(childC, self).__init__()，程序就會無限遞歸下去。

如：

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()

  File "C:/Users/Administrator/Desktop/crawler/learn.py", line 10, in __init__

    super(childC, self).__init__()RuntimeError: maximumrecursiondepthexceededwhile calling a Pythonobject

4、super()可以避免重復(fù)調(diào)用

如果childA基礎(chǔ)Base, childB繼承childA和Base，如果childB需要調(diào)用Base的__init__()方法時，就會導(dǎo)致__init__()被執(zhí)行兩次：

class Base(object):

    def__init__(self):

        print 'Base create'

 class childA(Base):

    def__init__(self):

        print 'enter A '

        Base.__init__(self)

        print 'leave A'

 

 class childB(childA, Base):

    def__init__(self):

        childA.__init__(self)

        Base.__init__(self)

 

b = childB()

Base的__init__()方法被執(zhí)行了兩次

enter A

Basecreate

leave A

Basecreate

使用super()是可避免重復(fù)調(diào)用

class Base(object):

    def__init__(self):

        print 'Base create'

 class childA(Base):

    def__init__(self):

        print 'enter A '

        super(childA, self).__init__()

        print 'leave A'

 

 class childB(childA, Base):

    def__init__(self):

        super(childB, self).__init__()

 

b = childB()

print b.__class__.mro()

enter A

Basecreate

leave A[<class '__main__.childB'>, <class '__main__.childA'>, <class '__main__.Base'>, <type 'object'>]

 

來源：伯樂在線