example-code-2e/20-executors/demo_executor_map.py

"""
Experiment with ``ThreadPoolExecutor.map``
"""
# tag::EXECUTOR_MAP[]
from time import sleep, strftime
from concurrent import futures

def display(*args):  # <1>
    print(strftime('[%H:%M:%S]'), end=' ')
    print(*args)

def loiter(n):  # <2>
    msg = '{}loiter({}): doing nothing for {}s...'
    display(msg.format('\t'*n, n, n))
    sleep(n)
    msg = '{}loiter({}): done.'
    display(msg.format('\t'*n, n))
    return n * 10  # <3>

def main():
    display('Script starting.')
    executor = futures.ThreadPoolExecutor(max_workers=3)  # <4>
    results = executor.map(loiter, range(5))  # <5>
    display('results:', results)  # <6>
    display('Waiting for individual results:')
    for i, result in enumerate(results):  # <7>
        display(f'result {i}: {result}')

if __name__ == '__main__':
    main()
# end::EXECUTOR_MAP[]