python 子類繼承父類的__init__方法

父類A

class A(object):
    def __init__(self, name):
        self.name=name
        print "name:", self.name
    def getName(self):
        return 'A ' + self.name

子類不重寫__init__，實例化子類時，會自動調用父類定義的__init__

class B(A):
    def getName(self):
        return 'B '+self.name
 
if __name__=='__main__':
    b=B('hello')
    print b.getName()

執行

$python lei2.py 
name: hello
B hello

但重寫了__init__時，實例化子類，就不會調用父類已經定義的__init__

class A(object):
    def __init__(self, name):
        self.name=name
        print "name:", self.name
    def getName(self):
        return 'A ' + self.name

class B(A):
    def __init__(self, name):
        print "hi"
        self.name =  name
    def getName(self):
        return 'B '+self.name

if __name__=='__main__':
    b=B('hello')
    print b.getName()

執行

$python lei2.py 
hi
B hello

為了能使用或擴展父類的行為，最好顯示調用父類的__init__方法

class A(object):
    def __init__(self, name):
        self.name=name
        print "name:", self.name
    def getName(self):
        return 'A ' + self.name

class B(A):
    def __init__(self, name):
        super(B, self).__init__(name)
        print "hi"
        self.name =  name
    def getName(self):
        return 'B '+self.name

if __name__=='__main__':
    b=B('hello')
    print b.getName()

執行

$python lei2.py
name: hello
hi
B hello