Reactive programming is a paradigm that aims at building better concurrent systems. Reactive applications are designed to comply with the requirements exemplified by the reactive manifesto:

• Responsive:  The system responds immediately to the user.
• Elastic: The system is capable of handling different levels of load and is able to adapt to accommodate increasing demands.
• Resilient: The system deals with failure gracefully. This is achieved by modularity and avoiding having a single point of failure.
• Message driven: The system should not block and take advantage of events and messages. A message-driven application helps achieve all the previous requirements.

As you can see, the intent of reactive systems is quite noble, but how exactly does reactive programming work? In this section, we will learn about the principles of reactive programming using the RxPy library.