Python 在子類中調用父類方法詳解（單繼承、多層繼承、多重繼承）
by:授客 QQ：1033553122
測試環境：
win7 64位
Python版本：Python 3.3.5
代碼實踐：
1、在子類中通過“類名”調用父類的方法
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
FatherA.__init__(self) # 在子類中調用父類的方法：父類名.方法名稱(參數)
if __name__ == '__main__':
b = SubClassB()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass B
init action in father class A
缺點：當一個子類的父類發生變化時（如類SubClassB的父類由FatherA變為FatherD時），必須遍歷整個類定義，把子類中所有的父類類名全部替換過來
2、在子類中通過“super”方法調用父類的方法
場景1、單層繼承
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in father class B')
super().__init__() # 在子類中調用父類的方法：super().方法名稱(參數)
if __name__ == '__main__':
b = SubClassB()
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super(SubClassB, self).__init__() # 在子類中調用父類的方法：super(type, obj).方法名稱(參數)
if __name__ == '__main__':
b = SubClassB()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in father class B
init action in father class A
說明：
1、super(type, obj)，其中obj必須是type類型、type子類類型的實例，否則會報錯：
TypeError: super(type, obj): obj must be an instance or subtype of type
2、super().__init__() 效果等同 super(SubClassB, self). __init__()
場景2、多層繼承
實驗1：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super().__init__()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
init action in subclass B
init action in father class A
對比實驗1-1：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super(SubClassB, self).__init__()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
init action in father class A
>>>
對比實驗1-2：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super(FatherA, FatherA).__init__(self) # 在子類中調用父類的方法：super(type, type).方法名稱(參數)
if __name__ == '__main__':
b = SubClassC()
說明：可把 super(FatherA, FatherA).__init__(self) 換成：
super(FatherA, self).__init__()
或
super(FatherA, SubClassB).__init__(self)
或
super(FatherA, SubClassC).__init__(self)
注意：以上這種情況，必須給__init__傳遞參數self，否則會報錯：
TypeError: __init__() missing 1 required positional argument: 'self'
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
>>>
說明：super(type1, type2) ，type2必須和type1相同類型，或者其子類類型
實驗2：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super().__init__()
class SubClassD(SubClassC):
def __init__(self):
print('init action in subclass D')
super().__init__()
if __name__ == '__main__':
b = SubClassD()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass D
init action in subclass C
init action in subclass B
init action in father class A
對比實驗2-1：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super().__init__()
class SubClassD(SubClassC):
def __init__(self):
print('init action in subclass D')
super(SubClassB, self).__init__()
if __name__ == '__main__':
b = SubClassD()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass D
init action in father class A
>>>
對比實驗2-2：
class FatherA:
def __init__(self):
print('init action in father class A')
class SubClassB(FatherA):
def __init__(self):
print('init action in subclass B')
super().__init__()
class SubClassC(SubClassB):
def __init__(self):
print('init action in subclass C')
super().__init__()
class SubClassD(SubClassC):
def __init__(self):
print('init action in subclass D')
super(SubClassC, self).__init__()
if __name__ == '__main__':
b = SubClassD()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass D
init action in subclass B
init action in father class A
通過對比實驗2-1， 2-2，可看出super(type[,type2_or_obj]),type決定了super調用方法所在的父類--type的父類（如果有的話），即type決定了前往哪個父類調用指定的方法
場景3、多重繼承
實驗1：
class FatherA:
def __init__(self):
print('init action in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
super(FatherB).__init__()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
對比實驗1-1：
class FatherA:
def __init__(self):
print('init action in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
class SubClassC(FatherB, FatherA):
def __init__(self):
print('init action in subclass C')
super().__init__()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
init action in father class B
>>>
對比實驗1-2：
class FatherA:
def __init__(self):
print('init action in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
super().__init__()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
init action in father class A
>>>
對比實驗1-3：
class FatherA:
def __init__(self):
print('init action in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
super(FatherB).__init__()
if __name__ == '__main__':
b = SubClassC()
>>> ================================ RESTART ================================
>>>
init action in subclass C
對比實驗1-4：
class FatherA:
def __init__(self):
print('init action in father class A')
def testfn(self, arg):
print('testfn in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
def testfn(self):
print('testfn in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
super().testfn()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
Traceback (most recent call last):
File "C:/Users/Administrator/Desktop/1.py", line 21, in
b = SubClassC()
File "C:/Users/Administrator/Desktop/1.py", line 18, in __init__
super().testfn()
TypeError: testfn() missing 1 required positional argument: 'arg'
>>>
對比實驗1-5：
class FatherA:
def __init__(self):
print('init action in father class A')
def testfn(self):
print('testfn in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
def testfn(self, arg):
print('testfn in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
super().testfn()
if __name__ == '__main__':
b = SubClassC()
運行結果：
>>> ================================ RESTART ================================
>>>
init action in subclass C
testfn in father class A
說明：通過對比實驗1-1，1-2，1-3，1-4，1-5可以看出，子類水平方向上，繼承多個父類，以super().method(參數)方法調用父類的方法，如果不同父類中存在同名方法method(不管參數列表是否相同)，則按繼承順序，選擇第一個父類中的方法。，如果想要調用多個方法咋辦？如下，通過類名調用
class FatherA:
def __init__(self):
print('init action in father class A')
class FatherB:
def __init__(self):
print('init action in father class B')
class SubClassC(FatherA, FatherB):
def __init__(self):
print('init action in subclass C')
FatherA.__init__(self)
FatherB.__init__(self)
if __name__ == '__main__':
b = SubClassC()
>>> ================================ RESTART ================================
>>>
init action in subclass C
init action in father class A
init action in father class B
>>>