The Concept of the Asynchronous Programing in Python

Introduction of the Asynchronous Programing

The propose of the asynchronous programing is to prevent our process from blocking by the file or network I/O operation. In python, we can idle the operation with the I/O bound through the OS until it done with event loop in asyncio module.

What is EventLoop?

Eventloop use the system call such as select, poll, epoll to monitor the state of the I/O operation, while the python program encounter the specified I/O operation then the task would be pended and handled by the system call. When the I/O operation is finished and return the results, then the pending task call back function would be invoked and notify that the task is done.

Concepts of the EventLoop and asyncio Module

• Each python thread has only one EventLoop. EventLoop in different threads is a different object, which means it’s a thread-local instance

• The contextvars.ContextVar in each task of the EventLoop has already live in the contextvars.copy_context()

• The Task before putting in the EventLoop is called Coroutine object, Coroutine object is the instance of the coroutine function which can be specified by async def

• The I/O asynchronous operation also can execute in thread or process through loop.run_in_executor() method which do not handle the I/O bound through system call directly and the object type in the EventLoop is Future.

Comparing the Future and Task

• Both are the awaitable type

• Future is the parent class of Task

• The Task is represent for the unit of the work scheduled and executed by the EventLoop

• Future is represent for the computation that may have not completed yet

Reference

Python Asyncio: The Complete Guide

Youtube: import asyncio: Learn Python’s AsyncIO