concurrent.futures help

[samuelbachorik]

Hi i want to ask you what is the difference betwen map() and submit()

Two codes examples

        with concurrent.futures.ProcessPoolExecutor() as executor:

            results = [None] * 50
            for x in range(50):
                results[x] = executor.map(function)

        with concurrent.futures.ProcessPoolExecutor() as executor:

            results = [None] * 50
            for x in range(50):
                results[x] = executor.submit(lfunction)

[Yoriz]

submit(fn, /, *args, **kwargs)
Schedules the callable, fn, to be executed as fn(*args **kwargs) and returns a Future object representing the execution of the callable

---

map(func, *iterables, timeout=None, chunksize=1)
Similar to map(func, *iterables) except:

• The iterables are collected immediately rather than lazily;
  
• func is executed asynchronously and several calls to func may be made concurrently.
  

---

I used ThreadPoolExecutor as ProcessPoolExecutor never works for me

from concurrent.futures import ThreadPoolExecutor


def func(value):
    return str(value)


with ThreadPoolExecutor() as executor:

    results = []
    for number in range(50):
        results.append(executor.submit(func, number))


print([result.result() for result in results])

with ThreadPoolExecutor() as executor:
    results = list(executor.map(func, range(50)))

print(results)

Output:
['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41', '42', '43', '44', '45', '46', '47', '48', '49']
['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41', '42', '43', '44', '45', '46', '47', '48', '49']

[bowlofred]

Hi i want to ask you what is the difference betwen map() and submit()

map() can be very convenient because you get the actual result from it rather than have to process a collection of future objects. Often this is sufficient.

What you lose from it is that the results must be returned in order. Most of the time that's fine, but there are some situations where you'd rather have the flexibility of being able to process in completion order instead. Also, any exceptions thrown by any child will stop the entire map(). If you want to process the data from the ones without exceptions, you need to work with the future objects yourself.