Asynchronous I/O and the real-time web [EuroPython 2017 - Talk - 2017-07-11 - Arengo] [Rimini, Italy] Building web applications is one of the most common uses of Python. With a plethora of different web frameworks aiming at varying audiences, it has become a rather simple and well-documented process to develop web applications and web services. So popular it has become that the WSGI specification is the industry standard protocol for developing web applications with Python. But the WSGI standard is lacking with two major limitations: It supports only the ‘traditional’ synchronous http request-response cycle thus creating a ‘glass ceiling’ with the amount of requests a single server can handle – often described as the C10K problem It does not provide an easy and efficient way of developing two-way communication between servers and clients. Often referred to as the real-time web this capability has become increasingly popular with modern web applications. Over the past decade multiple networking libraries have been developed to address these limitations. In this talk we will explore: What is an asynchronous web server and how it differs from other, WSGI-based web servers. What is concurrency and how it can help us achieve supreme performance and scalability in our web applications. We will survey noteworthy libraries which will help achieve true concurrency. How to develop real-time communication, using web sockets, with our Javascript application Concerns, limitations and pitfalls when developing asynchronous web applications