multiprocessing_example.py

import multiprocessing
import time


inputs = ["a", "b", "c", "d"]

def slow_func(x: str) -> str:
    print(f"converting {x} to {x + x}...")
    time.sleep(1)
    return x + x

print("starting slow sequential loop")
start = time.time()
results = []
for i in inputs:
    results.append(slow_func(i))
print("done. results:", results)
print(f"time taken: {time.time() - start:.2f}s")

print()
print("starting fast parallel loop")
start = time.time()
with multiprocessing.Pool(processes=4) as pool:
    results = pool.map(slow_func, inputs)
print("done. results:", results)
print(f"time taken: {time.time() - start:.2f}s")

Output:

starting slow sequential loop
converting a to aa...
converting b to bb...
converting c to cc...
converting d to dd...
done. results: ['aa', 'bb', 'cc', 'dd']
time taken: 4.00s

starting fast parallel loop
converting a to aa...
converting b to bb...
converting c to cc...
converting d to dd...
done. results: ['aa', 'bb', 'cc', 'dd']
time taken: 1.02s