AsyncIO - Implementing AsyncIO

To understand how the asyncio Python standard library works and provides asynchronous I/O via async/await syntax. We are going to reimplement it from scratch.

Rewind: Coroutines

coroutine Coroutines are a more generalized form of subroutines. Subroutines are entered at one point and exited at another point. Coroutines can be entered, exited, and resumed at many different points.

Source

AsyncIO in Python is based on coroutines. We already know Generators/Iterators are coroutines. Generators allow suspend the current function and to return to the caller of the function.

Overview

We are going to re-implement the asyncio Python standard library step-by-step as it was provided with Python 3.4 initially. This allows for understanding it’s internals and general concept. Of course we are using simplifications and skipping some parts like cancellation. These parts are mentioned in the What’s missing chapter.

• Step 1 - Coroutine Concept
• Step 2 - Multiple Coroutines
• Step 3 - Adding yield from
• Step 4 - A Loop is running
• Step 5 - A runnable Example
• Step 6 - The Intermediate Function Issue
• Step 7 - The Future
• Step 8 - Extend the Loop
• Step 9 - A Job has to be done
• Step 10 - Scheduling all the time
• Step 11 - Schedule Callbacks
• Step 12 - Back to the Future
• Step 13 - Deduplicate Running Coroutines
• Step 14 - Let’s wait
• Step 15 - And what about real Async IO?
• Step 16 - Cancellation
• What’s missing?
• The Coroutine/Generator Issue