[Python-Dev] [PEP 3148] futures - execute computations asynchronously (original) (raw)

Brian Quinlan brian at sweetapp.com
Fri Mar 5 07:03:02 CET 2010

Hi all,

I recently submitted a daft PEP for a package designed to make it
easier to execute Python functions asynchronously using threads and
processes. It lets the user focus on their computational problem
without having to build explicit thread/process pools and work queues.

The package has been discussed on stdlib-sig but now I'd like this
group's feedback.

The PEP lives here: http://python.org/dev/peps/pep-3148/

Here are two examples to whet your appetites:

"""Determine if several numbers are prime.""" import futures import math

PRIMES = [ 112272535095293, 112582705942171, 112272535095293, 115280095190773, 115797848077099, 1099726899285419]

def is_prime(n): if n % 2 == 0: return False

 sqrt_n = int(math.floor(math.sqrt(n)))
 for i in range(3, sqrt_n + 1, 2):
     if n % i == 0:
         return False
 return True

Uses as many CPUs as your machine has.

with futures.ProcessPoolExecutor() as executor: for number, is_prime in zip(PRIMES, executor.map(is_prime,
PRIMES)): print('%d is prime: %s' % (number, is_prime))

"""Print out the size of the home pages of various new sites (and Fox
News).""" import futures import urllib.request

URLS = ['http://www.foxnews.com/', 'http://www.cnn.com/', 'http://europe.wsj.com/', 'http://www.bbc.co.uk/', 'http://some-made-up-domain.com/']

def load_url(url, timeout): return urllib.request.urlopen(url, timeout=timeout).read()

with futures.ThreadPoolExecutor(max_workers=5) as executor: # Create a future for each URL load. future_to_url = dict((executor.submit(load_url, url, 60), url) for url in URLS)

 # Iterate over the futures in the order that they complete.
 for future in futures.as_completed(future_to_url):
     url = future_to_url[future]
     if future.exception() is not None:
         print('%r generated an exception: %s' % (url,

future.exception())) else: print('%r page is %d bytes' % (url, len(future.result())))

Cheers, Brian

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