[Python-Dev] [PEP 3148] futures - execute computations asynchronously

[Brian Quinlan]

On 6 Mar 2010, at 07:38, Brett Cannon wrote:

> The PEP says that futures.wait() should only use keyword arguments  
> past its first positional argument, but the PEP has the function  
> signature as ``wait(fs, timeout=None, return_when=ALL_COMPLETED)``.   
> Should it be ``wait(fs, *, timeout=None, return_when=ALL_COMPLETED)``?

Hi Brett,

That recommendation was designed to make it easy to change the API  
without breaking code.

I'd don't think that recommendation makes sense anymore any I'll  
update the PEP.

Cheers,
Brian

> On Thu, Mar 4, 2010 at 22:03, Brian Quinlan <brian at sweetapp.com>  
> wrote:
> 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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