Explanation on the usage of python destructor and constructor

class Test(object):
    def __init__(self, name):
        self.name = name
        print('这是构造函数')

    def say_hi(self):
        print('hell, %s' % self.name)

    def __del__(self):
        print('这是析构函数')

obj = Test('bigberg')

obj.say_hi()

del obj

#输出
　　这是构造函数


　　hello bigberg


　　这是析构函数

　

Constructor

Used to initialize the content state of the class, the constructor type __init__() provided by Python, That is, this function will be executed when the class is instantiated. The __init__() method is optional. If not provided, Python will give the default __init__ method.

Destructor

"__del__" is a destructor. When del is used to delete an object, its own destructor will be called. In addition, when the object After being called in a certain scope, the destructor will be called once when jumping out of its scope, which can be used to release memory space.

__del__() is also optional. If not provided, Python will provide a default destructor in the background

If you want to explicitly call the destructor, you can use the del keyword: del obj

Garbage collection mechanism　

s = '123'
print('del...running')
del s

When we use del to delete an object, the memory space of the object is not directly cleared. Python uses a 'reference counting' algorithm to handle recycling, that is: when an object is no longer referenced by other objects within its scope, Python automatically clears the object.

The destructor __del__() will automatically clear the memory space of the deleted object when it is referenced.

Constructor:

Used to initialize the content state of the class, the constructor type provided by Python is __init__();

That is, this function will be executed when the class is instantiated. Then we can put the properties to be initialized first into this function. The following program:

__init__() method is optional. If not provided, Python will give the default __init__ method

General data Get the get and set methods that need to be defined

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