The interactivity and functionality of your data dashboards and web applications with Python depend on the logic and code you write to handle user input and output. Interactivity refers to how you enable users to manipulate and explore the data, such as filtering, sorting, zooming, or selecting. Functionality refers to how you perform the data analysis and processing, such as calculations, transformations, or visualizations. To implement interactivity and functionality, use callbacks or decorators to define functions that execute when users interact with elements. Variables or data structures should be used to store and update data and application states. Data manipulation libraries such as pandas, numpy, or scipy should be used for data operations. Visualization libraries such as plotly, matplotlib, or seaborn should be used for creating and customizing charts and graphs that display the data. Interactive features such as tooltips, legends, or annotations should be used to enhance user experience. Error handling and debugging techniques should be used to catch and fix errors or bugs that may occur in your code. Logging and testing tools should also be used to monitor and improve the performance and quality of your application.