Detailed interpretation of the __init__() method in Python
Notes on the __init__ method in Python
Summary of several methods of python's __init__
Explain in detail __init__ and __new__ in Python
The __new__ method is a method of creating a class instance , called when an object is created, and returns an instance of the current object
The __init__ method is called after the class instance is created , some initialization of the current object instance, no return value
Note 1. __init__ is not equivalent to the constructor in C#. When it is executed, the instance has been constructed.
class A(object):
def __init__(self,name):
self.name=name
def getName(self):
return 'A '+self.name
when we execute
a=A('hello')
, can be understood as
a=object.__new__(A) A.__init__(a,'hello')
That is, the role of __init__ is to initialize the instantiated object.
Note 2. The subclass can not rewrite __init__. When instantiating the subclass,the __init__ defined in the superclass will be automatically called
class B(A):
def getName(self):
return 'B '+self.name
if __name__=='__main__':
b=B('hello')
print b.getName()
But if __init__ is overridden , when instantiating a subclass, it will not implicitly call the __init__ defined in the superclass
class C(A):
def __init__(self):
pass
def getName(self):
return 'C '+self.name
if __name__=='__main__':
c=C()
print c.getName()
It will report "AttributeError: 'C' object has no attribute 'name'" error, so if __init__ is overridden, in order to use or extend the behavior in the superclass, it is best to explicitly call the superclass's __init__ method
class C(A):
def __init__(self,name):
super(C,self).__init__(name)
def getName(self):
return 'C '+self.name
if __name__=='__main__':
c=C('hello')
print c.getName()
。。。