Tutorial

Prerequisites

To work through the example code in this chapter, first install Python and DeltaCycle.

See Installation for how to install DeltaCycle.

For brevity, all code examples assume you have executed the following prelude:

from deltacycle import *

Hello World

For DeltaCycle, the simplest program to print “Hello, world!” is:

async def main():
    print("Hello, world!")

run(main())

The async def main(): ... code block declares a coroutine function. The run function wraps an instance of the main coroutine in a task, and schedules that task to execute as soon as possible.

Output:

Hello, world!

See Coroutines in the official Python documentation for background.

Consuming Time

A simulation is a model of how a system’s state evolves over time. DeltaCycle coroutines simulate the passage of time with the sleep function. The now function returns the current simulation time, which can be handy for debug, measurement, and analysis.

async def main():
    print(now(), "Enter")
    await sleep(1)
    print(now(), "foo")
    await sleep(1)
    print(now(), "bar")
    await sleep(1)
    print(now(), "Exit")

run(main())

The main coroutine executes four print statements, each separated by one unit of time. The simulation clock starts at time 0.

Output:

0 Enter
1 foo
2 bar
3 Exit