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A library of composable Python executors and futures

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This library is intended for use with the concurrent.futures module. It includes a collection of Executor implementations in order to extend the behavior of Future objects.


  • Futures with implicit retry
  • Futures with implicit cancel on executor shutdown
  • Futures with implicit cancel after timeout
  • Futures with transformed output values (sync & async)
  • Futures resolved by a caller-provided polling function
  • Throttle the number of futures running at once
  • Synchronous executor
  • Bridge concurrent.futures with asyncio
  • Convenience API for creating executors
  • Instrumented with Prometheus

See the API documentation for detailed information on usage.


This example combines the map and retry executors to create futures for HTTP requests running concurrently, decoding JSON responses within the future and retrying on error.

import requests
from concurrent.futures import as_completed
from more_executors import Executors

def get_json(response):
    return (response.url, response.json())

def fetch_urls(urls):
    # Configure an executor:
    # - run up to 4 requests concurrently, in separate threads
    # - run get_json on each response
    # - retry up to several minutes on any errors
    executor = Executors.\

    # Submit requests for each given URL
    futures = [executor.submit(requests.get, url)
               for url in urls]

    # Futures API works as normal; we can block on the completed
    # futures and map/retry happens implicitly
    for future in as_completed(futures):
        (url, data) = future.result()
        do_something(url, data)


virtualenv and pip may be used to locally install this project from source:

virtualenv ~/dev/python
. ~/dev/python/bin/activate

git clone
cd more-executors

pip install --editable .

Autotests may be run with pytest:

pip install -r test-requirements.txt

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This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

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