There are many ways to implement Singleton pattern in Python, and the following two common methods are given. 1. Use module level variables: ```python class Singleton: Single instance class def __new__(cls, *args, **kwargs): if not hasattr(cls, '_instance'): cls._instance = super().__new__(cls, *args, **kwargs) return cls._instance #Usage examples obj1 = Singleton() obj2 = Singleton() print(obj1 is obj2) # True ``` 2. Use decorators: ```python def singleton(cls): instances = {} def wrapper(*args, **kwargs): if cls not in instances: instances[cls] = cls(*args, **kwargs) return instances[cls] return wrapper @singleton class Singleton: Single instance class pass #Usage examples obj1 = Singleton() obj2 = Singleton() print(obj1 is obj2) # True ``` Both of the above methods can implement the Singleton pattern to ensure that there is only one instance in the program. The implementation principle is through rewriting`__ New__` Method to control the instantiation process and ensure that only one instance is created.

In the Spring framework, a Singleton pattern bean is a bean that only has one instance in the application. The life cycle of a singleton bean is managed by using the Spring container. Using the Singleton pattern can save system resources and improve performance. In Spring, by default, all beans are singleton. The complete source code of the Singleton pattern bean in the Spring framework is shown below: ```java public class SingletonBean { private static SingletonBean instance; private SingletonBean() { //Private Constructor } public static synchronized SingletonBean getInstance() { if (instance == null) { instance = new SingletonBean(); } return instance; } public void doSomething() { //Perform certain actions } } ``` In the above code, the SingletonBean class is a bean in Singleton pattern. It only has a private static instance variable instance, which is obtained through the getInstance() method. The getInstance () method is synchronized to ensure Thread safety. Within the method, if instance is null, create a new instance; Otherwise, return the existing instance directly. The bean of the Singleton pattern can be referenced in different places of the application. Any component that needs to use the bean can obtain the instance by calling the getInstance() method, and then use the instance method to perform the corresponding operation. Summary: 1. The Singleton pattern bean in the Spring framework is a bean that only has one instance in the application. By default, all beans in the Spring framework are singleton. 3. Singleton pattern beans manage their life cycle through the Spring container. 4. Using the Singleton pattern can save system resources and improve performance. 5. In Spring, you can call the getInstance() method to obtain the instance of the Singleton pattern bean. 6. Beans in the Singleton pattern can be referenced in different parts of the application and can perform corresponding operations.