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This article focuses on "what are the ways to implement the singleton pattern in Python", interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what are the ways to implement singleton patterns in Python?"

Singleton pattern (Singleton Pattern) is a commonly used software design pattern whose main purpose is to ensure that only one instance of a class exists. Singleton objects come in handy when you want only one instance of a class to appear in the entire system.

For example, the configuration information of a server program is stored in a file, and the client reads the configuration file information through an AppConfig class. If you need to use the contents of the configuration file in many places during the running of the program, that is to say, you need to create instances of AppConfig objects in many places, which results in multiple instance objects of AppConfig in the system, which will be a serious waste of memory resources, especially in the case of a lot of configuration files. In fact, for classes like AppConfig, we want only one instance object to exist while the program is running.

1. Use module

You can refer to the custom addition, deletion, modification and query component site object, which is an obvious single-interest mode.

In fact, the Python module is a natural singleton mode, because the module generates a .pyc file the first time it is imported, and loads the .pyc file directly on the second import without executing the module code again. Therefore, we only need to define the relevant functions and data in a module to get a singleton object. If we really want a singleton class, consider doing this:

Save the above code in the file mysingleton.py, and then use:

two。 Use new

Add a lock

3. Use classes to implement singleton patterns:

a. Singleton mode that cannot support multithreading

But let's try multithreading.

Results:

b. Solve the above problems and implement a single-column mode that supports multithreading:

Results:

Question:

Creating an instance can only be called by calling Singleton.instance (), not with Singleton ().

4. Implementation based on metaclass

1. An object is a class creation. The _ _ init__ method of the class is automatically executed when the object is created, and the object () executes the _ _ call__ method of the class 2. The class is created by type. The _ _ init__ method of type is automatically executed when the class is created, and the class () executes the _ _ call__ method of type (_ _ new__ method of the class, _ _ init__ method of the class)

Implementation singleton:

At this point, I believe you have a deeper understanding of "what are the ways to implement the singleton pattern in Python?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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