Benefits of asyncio with Python3?

Question

I have read that asyncio is a great addition to Python 3. I have looked around and saw the related PEP which is quite big BTW but couldn't find a simple explanation for why this is such a great addition. Any simple example where it can be used?

It can be used to have a queue of tasks? Like threads? Maybe light weight threads? Those were my thoughts but the library reference clearly stated that this is single-threaded. So there should be some waiting time in between the tasks. Then what is good?

These are just jumbled thoughts that came into my mind while trying to make sense of usefulness of asyncio. Anyone can give a better idea?

Answer 1

You're right, neither the PEP nor the docs to much to motivate the module's existence. I suggest that you look at the following link
http://en.wikipedia.org/wiki/Asynchronous_I/O

The asynchronous model lets you initiate a task (typically an I/O task) that would normally block, and then go on to do other things (like initiating more tasks) while waiting on that task, without having to resort to multiple threads or processes (which have the disadvantages of consuming more system resources as well as introducing the risk of race conditions and deadlocks).

It does this by using callbacks; when a task is complete, a callback is called that handles its completion. Often in asynchronous code you end up with large networks of callbacks that can be confusing to follow and debug because nothing ever gets called directly. One of the significant features of the asyncio module is that it allows asynchronous programming using co-routines, where the callbacks are abstracted away and essentially have the effect of resuming the co-routine when the task completes. Thus you end up writing code that looks a lot like threaded, sequential code with none of the pitfalls.