Goroutines in Mercury

Based on the input provided, the target language is Python. Here’s the translated example and explanation in Markdown format suitable for Hugo:

A goroutine is a lightweight thread of execution.

import threading
import time

def f(from_):
    for i in range(3):
        print(from_, ":", i)

def main():
    # Call the function in the usual way, running it synchronously.
    f("direct")

    # To invoke this function in a thread, use threading.
    # This new thread will execute concurrently with the calling one.
    thread = threading.Thread(target=f, args=("thread",))
    thread.start()

    # You can also start a thread for an anonymous function call.
    threading.Thread(target=lambda: print("going")).start()

    # Wait for the threads to finish (using join for a more robust approach).
    time.sleep(1)
    print("done")

if __name__ == "__main__":
    main()

Suppose we have a function call f(s). Here’s how we’d call that in the usual way, running it synchronously:

f("direct")

To invoke this function in a thread, use threading.Thread. This new thread will execute concurrently with the calling one:

thread = threading.Thread(target=f, args=("thread",))
thread.start()

You can also start a thread for an anonymous function call:

threading.Thread(target=lambda: print("going")).start()

Our two function calls are running asynchronously in separate threads now. Wait for them to finish (for a more robust approach, use join on threads):

time.sleep(1)
print("done")

When we run this program, we see the output of the blocking call first, then the output of the two threads. The threads’ output may be interleaved, because threads are being run concurrently by the Python interpreter:

$ python goroutines.py
direct : 0
direct : 1
direct : 2
thread : 0
going
thread : 1
thread : 2
done

Next, we’ll look at a complement to threads in concurrent Python programs: queues.

Next example: Channels.