【轉(zhuǎn)】python類中super()和__init__()的區(qū)別

單繼承時(shí)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：

Base create creat A Base create creat B Base create

區(qū)別是使用super()繼承時(shí)不用顯式引用基類。

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(shí)，在初始化b時(shí)就會(huì)報(bào)錯(cuò)：

super(childB, self).__init__() TypeError: must be type, not classobj

super不是父類，而是繼承順序的下一個(gè)類

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

def super(class_name, self):mro = self.__class__.mro()return mro[mro.index(class_name) + 1]

mro()用來(lái)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):passc = childC() print c.__class__.__mro__

輸出結(jié)果如下：

enter A enter B Base create leave B leave A (<class '__main__.childC'>, <class '__main__.childA'>, <class '__main__.childB'>, <class '__main__.Base'>, <type 'object'>)

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

執(zhí)行過(guò)程相當(dāng)于：初始化childC()時(shí)，先會(huì)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(gè)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(shí)，繼承childA后就會(huì)直接跳到Base類里，而略過(guò)了childB：

enter A Base create 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(gè)參數(shù)可以是繼承鏈中任意一個(gè)類的名字，

如果是本身就會(huì)依次繼承下一個(gè)類；

如果是繼承鏈里之前的類便會(huì)無(wú)限遞歸下去；

如果是繼承鏈里之后的類便會(huì)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(huì)無(wú)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: maximum recursion depth exceeded while calling a Python object

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(shí)，就會(huì)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 Base create leave A Base create

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

轉(zhuǎn)載于:https://www.cnblogs.com/langqi250/p/10032077.html

總結(jié)

以上是生活随笔為你收集整理的【转】python类中super()和__init__()的区别的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。