Professional Python

Chapter 13asyncio

In general, most Python applications are sequential applications. That is, they usually run from a defined entry point to a defined exit point, with each execution being a single process from beginning to end.

This stands in contrast to many more asynchronous languages, such as JavaScript and Go. For example, JavaScript relies heavily on asynchronous work, with any web requests happening in the background being called in a separate thread, and relying on callbacks to run correct functions once data has loaded.

There is no right or wrong answer to whether a language should approach most problems sequentially or asynchronously, but cases certainly exist where one model is more useful than the other for particular problems. This is where the asyncio module comes in. It makes it easy to do asynchronous work in Python when the problem warrants it.

Right now, asyncio is a provisional module. While sweeping, backward-incompatible changes are unlikely (because Python shies away from such things once items have been placed in the standard library), it is likely that asyncio may undergo significant revision in the next couple of Python versions.

The asyncio module was introduced in Python 3.4, and is not available in Python 2. If you are on Python 3.3, you can get it from PyPI; it is not yet in the standard library. Therefore, if you want to use the features provided by asyncio, you will be limiting yourself to newer versions of Python. Similarly, the asyncio module ...