python class destructor

Declare Destructors virtual in polymorphic base classes 1. Why declare a virtual function?In C ++ programming, a base class usually has multiple derived types, while most of the base classes are pure virtual functions, which require implementation of derived types. In this case, a base type pointer is returned by using the factory mode. In C ++, it is clearly pointed out that a derived type is deleted by a base type pointer, and the result of this bas

This blog (http://blog.csdn.net/livelylittlefish) posted by the author (three two one, small fish) related research, learning content of the notes made, welcome to the majority of friends correct! Define a base class and two Derived classes, define their objects respectively, and observe the following code for calling the construction and destructor: /**//*********************************** ****************

Recently done a project is based on PHP4, accustomed to PHP5 face object, face PHP4, inevitably will have a lot of uncomfortable: Does not support the public, static, private, protected keywords, the most depressing is that the destructor is not supported: This article will use PHP's register_shutdown_function to simulate a class's destructor in PHP4 In the constructor, we register the

After you create an object with a constructor, the program keeps track of the object until it expires. After the object expires, the program calls the destructor to complete the cleanup of the object.Several features of the destructor:1. There can be only one destructor, and if there is no explicit definition, the compiler will automatically generate a default

//constructorofclassderivedfromtemplateclass.cpp:Defines the entry point for the console Application. #include "stdafx.h" template Derived classes default constructor constructors for template base classes non-default constructor copy constructor overload assignment operator //Implicit call Yes Yes no no //can manually call Yes No Yes no //inheritance no no No Yes Yes //Overload No no no

Item 07-Declaring the virtual destructor for the polymorphic base classDeclare destructors virtual in polymorphic base classWhy? http://blog.csdn.net/wxqian25/article/details/7361069Ex: There are several ways to record time, a base class and some derived classesClass timekeeper{//base classPublicTimekeeper ();~timekeeper ();...}Class Atomicclock:public timekeeper

You are welcome to repost the post, but please mark the author as "nine days Yan Ling". Of course, the link to this post is better. Without knowing it, I have written six lectures. It is true that this learning can force me to really debug the code in every book, think about something that you can tell you about in a new book. This is really learning. After reading the book, I thought I had mastered it, it doesn't seem to work here in the class, becau

1. Reasons: When implementing polymorphism, when using a base class pointer to manipulate a derived class, prevent only the destructor of the base class without the destructor of the derived class at the time of the

1 Basic virtual destructor We know that the Destructor used for base classes during C ++ development are generally virtual functions. But why? Here is a small example:There are two classes: Class clxbase{Public:Clxbase (){};Virtual ~ Clxbase (){}; Virtual void dosomething () {cout }; Class clxderived: Public cl

Inherited constructor destructor Call of constructor and destructor in class inheritance Currently, there are three classes. The class definition is as follows: Class ca{Public:CA () {cout ~ CA () {cout }; Class CB: public CA{

1. Fictitious Function Definition A destructor is a special user-defined member function. When an object of this class leaves its domain or delete expression and is applied to the pointer of an object of this class, the Destructor is automatically called. The Destructor

C ++ class related issues, constructor and destructor, copy constructor instance explanations, constructor instance explanations The basic task of object-oriented is to describe the object and classify and summarize the object. The class type is the same as the int type, and there is no memory allocation. Class attrib

See the following code: Class {Public:A () {pvalue = new int [100]; printf ("constructor of A/N ");}~ A () {Delete [] pvalue; printf ("deconstructor of A/N ");}PRIVATE:Int * pvalue;};Class B {Public:~ B () {printf ("deconstructor of B/N ");}}; Class C: Public B {Public:~ C () {printf ("deconstructor of C/N ");}PRIVATE:A;}; Int main (INT argc, char * argv []){C;Re

is first constructed, then B, and finally a. To see an example, the above should be a bit: Copy Code code as follows: Class C { Public C () {printf ("c\n");} Protected Private }; Class B{PublicB () {printf ("b\n");}ProtectedPrivate}; Class A:public B{PublicA () {printf ("a\n");}Protectedc C;Private}; int main (){A A;GetC

Chapter 2 class constructor, destructor, and assignment function Constructors, destructor, and assignment functions are the most basic functions of each class. They are so common that they are easy to paralyze. In fact, these seemingly simple functions are as dangerous as the sewers without the top cover. Each

Remember:A base class with polymorphic properties should declare a virtual destructor. If class has any virtual functions, it should have a virtual destructor.The design purpose of class is not to declare a virtual destructor if it is not used as a base

/* When an object is established, the constructor of the base class is called first, and then the next derived class'sconstructor, and so on, until you reach the constructor of the most derived class that derives the most number of times.In short, objects are constructed from the "bottom up" start. Because, when a constructor is initially constructed, it is alwaysTo invoke the constructor of its base

In fact, this is a principle of effect c ++, but it is silly and stupid, always forget, write down the tunnel to remember. I: Class{Public:~ A (){Cout }}; Class B: public{Public:~ B (){Cout }}; Int _ tmain (INT argc, _ tchar * argv []){A * P = new B; // when P is released, it is called only the destructor of A because it is of the type. Delete P;Return 0;} So th

=pymysql.cursors.dictcursoR) #这样返回的就是字典def ex_sql (Self,sql):TrySelf.cur.execute (SQL)Except Exception as E:Print (' SQL statement problematic,%s '%sql)ElseSelf.res = Self.cur. Fetchall ()Return Self.res###Destructors Def __del__ (): Pass Executed when the instance is destroyed.######my = MyDb (' 118.24.3.40 ', ' jxz ', ' 123456 ', ' jxz ')My.ex_sql (' select * from Stu; ')Print (My.res)Print (' I'm the last line of code ...') #这里才会执行析构函数. The des