How to Use ThreadPoolExecutor for Concurrent Tasks in Python

import time
import threading
from concurrent.futures import ThreadPoolExecutor


def fetch_data(index):
    """Simulate a synchronous data fetch."""
    time.sleep(0.1)
    return f"data-{index}"


def run_sequential(total=10):
    """Run tasks one after another."""
    start = time.perf_counter()
    results = [fetch_data(i) for i in range(total)]
    elapsed = time.perf_counter() - start
    return results, elapsed


def run_threaded(total=10, workers=4):
    """Run tasks concurrently using a thread pool."""
    start = time.perf_counter()
    with ThreadPoolExecutor(max_workers=workers) as executor:
        results = list(executor.map(fetch_data, range(total)))
    elapsed = time.perf_counter() - start
    return results, elapsed


if __name__ == "__main__":
    seq_results, seq_time = run_sequential()
    thr_results, thr_time = run_threaded()

    print(f"Sequential: {seq_time:.3f}s -> {seq_results[:3]}...")
    print(f"Threaded  : {thr_time:.3f}s -> {thr_results[:3]}...")
    print(f"Speedup   : {seq_time / thr_time:.2f}x")