SOLID principles are essential in object-oriented design to improve flexibility, maintainability, and scalability of software. Single Responsibility Principle emphasizes that a class should have only one reason to change, leading to clearer, more maintainable code. Open/Closed Principle advocates for extending existing code rather than modifying it, promoting code reusability and stability. Liskov Substitution Principle ensures that subtypes can substitute their base types without affecting program correctness, maintaining consistency and reliability. Interface Segregation Principle suggests creating smaller, more focused interfaces to enhance flexibility and avoid unnecessary method implementations. Dependency Inversion Principle states that high-level modules should not depend on low-level modules, both should depend on abstractions, promoting decoupling through abstract interfaces. By adhering to these principles, software design becomes more robust and adaptable, benefiting from clearer structure and reduced coupling.

文章讨论了三种常见设计模式的 Python 实现。首先介绍了单例模式，通过实现一个数据库连接池管理器来说明单例模式的用法，确保系统中只有一个连接池实例。然后是工厂模式，设计一个支持多种数据格式解析的文件处理系统，包括 CSV、JSON、XML 和 YAML 格式的解析器。最后介绍观察者模式，实现股票市场监控系统，支持多种观察者类型，如邮件通知、短信通知和应用内通知。这些设计模式在软件架构设计中具有重要作用。