![]() ![]() This removes the currently running task from the ready list and adds it to a list that you specify. Way to represent forks (the eating kind, not the unix kind) and a wayįor a task to wait for one to become available.īut before launching into that, let's add two more functions to our scheduler that will come in useful. Let's turn our people into dining philosophers. Things get more interesting when our tasks do something non-trivial. We've got enough so far to try a simple test. When the task finishes, we use the following function to remove it from the scheduling system. Yielded, we move it to the end, so that the ready tasks will run If the task is still at the head of the ready list after it has The core loop of the scheduler will repeatedly take the task at the head of the queue and run it until it yields. The first thing we'll want is a way of getting a task into the scheduling system. We'll also want a queue of tasks that are waiting to run. We'll start with a global variable to hold the currently running task. We won't make any use of values sent or received by yields they will simply be suspension points. Whenever a task wants to suspend itself, it will yield. ![]() To help distinguish between them, I'll use aĬolour code: orange for library code, blue for application examples, and green for example output.Įach task will be a generator. Of code, some of which are core parts of the scheduler and some of Here I will develop a very simple scheduler for such tasks, to I will use the term task to refer to such threads, to distinguish them from OS-supported threads and processes. This is an essay about using generators, together with the new yield from construct available in Python 3.3, to implement lightweight cooperatively-scheduled threads. Simple Generator Scheduler Lightweight Tasks using Generators and Yield-From ![]()
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