SOLID principles, including Single Responsibility Principle (S), Open/Closed Principle (O), Liskov Substitution Principle (L), Interface Segregation Principle (I), and Dependency Inversion Principle (D), aim to improve software design flexibility, maintainability, and scalability. By adhering to these principles, classes can have clearer responsibilities, code can be more concise, and system stability can be enhanced. Violations of these principles can lead to tightly coupled code and increased maintenance costs. Following SOLID principles leads to better code organization, improved extensibility, and reduced risks associated with code modifications.

本文介绍了三种常见的设计模式的 Python 实现。首先是单例模式，通过实现一个数据库连接池管理器的单例模式，确保系统中只有一个连接池实例。其次是工厂模式，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 格式的文件解析器。最后是观察者模式，实现一个股票市场监控系统，当股票价格变化时通知注册的观察者，包括邮件通知、短信通知和应用内通知。这些设计模式提供了灵活的解决方案，用于架构设计中的实际应用场景。