__init__ () method in Python note points

This article goes from https://www.cnblogs.com/zyxstar2003/archive/2011/03/21/1989954.html

1, __init__ is not equivalent to the constructor in C #, when it is executed, instance has been constructedOut.

1 class A (object): 2     def __init__ (self,name): 3         Self.name=name4     def  getName (self):5          return'+self.name

When we execute

1 a=a ('hello')

, it can be understood as

1 a=object. __new__ (A) 2 A.__init__(A,'hello')

That is, the __init__ function is to initialize the object after it has been instantiated.

2, sub-class can be do not rewrite__init__, when instantiating subclasses, is automatically called__init__ defined in the superclass

1 classB (A):2     defGetName (self):3         return 'B'+Self.name4  5 if __name__=='__main__':6B=b ('Hello')7     PrintB.getname ()

However, if __init__ is overridden and the subclass is instantiated, the defined __init__ in the superclass are not implicitly called again

1 classC (A):2     def __init__(self):3         Pass4     defGetName (self):5         return 'C'+Self.name6  7 if __name__=='__main__':8C=C ()9     PrintC.getname ()

It will be reported "Attributeerror: ' C ' object has no attribute ' name '" error, so if __init__ is overridden, in order to be able to use or extend the behavior in the superclass, it is best to explicitly call the __init__ method of the Super class

1 classC (A):2     def __init__(self,name):3Super (C,self).__init__(name)4     defGetName (self):5         return 'C'+Self.name6  7 if __name__=='__main__':8C=c ('Hello')    9     PrintC.getname ()

__init__ () method in Python note points