Futures as they complete in Python

Reacting to results in finish order, not submit order.

from concurrent.futures import ThreadPoolExecutor, as_completed
import time


def job(name, seconds):
    time.sleep(seconds)
    return name


with ThreadPoolExecutor() as pool:
    futures = {pool.submit(job, f"task-{i}", i / 10): i
               for i in range(3, 0, -1)}
    order = []
    for future in as_completed(futures):
        order.append(future.result())  # fastest lands first

How it works

1. submit schedules each job and returns a future.
2. as_completed yields futures the moment they finish.
3. The fastest task lands first regardless of order.

Keywords and builtins used here

• as
• def
• for
• job
• range
• return
• with

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Step 4 of 4 in Threads & processes, step 31 of 53 in Pythonic Python.

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