Python 3.5 is a version of the popular programming language Python, released in September 2015. It introduced several new features, including the async/await syntax for asynchronous programming, which allows developers to write code that can handle multiple tasks at once more efficiently. This version also improved type hinting, making it easier to understand the types of variables used in the code. Additionally, Python 3.5 included enhancements to the standard library, such as new modules and functions that simplify common programming tasks. It aimed to improve performance and maintainability, making it a valuable tool for both beginners and experienced developers.