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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: c# async, await
Date: Thu, 22 Aug 2013 19:04:32 -0400
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On 8/22/2013 9:57 AM, Michael Torrie wrote:
> On 08/22/2013 05:29 AM, Neal Becker wrote:
>> So my son is now spending his days on c# and .net.  He's enthusiastic about
>> async and await, and said to me last evening, "I don't think python has anything
>> like that".  I'm not terribly knowledgeable myself regarding async programming
>> (since I never need to use it).  I did look at this:
>>
>> http://tirania.org/blog/archive/2013/Aug-15.html

The iterator protocol, introduced in 2.2, was explicitly intended (by 
Tim Peters) to replace many uses of synchonous callbacks.

This example from the blog, of callback replacement,

int sum_values (Hashtable hash)
{
	int sum = 0;
	hash.foreach ((key, value) => { sum += value; });
	return sum;
}

is written in Python *much more generally* as

def sum(iterable):
   sum = 0
   for item in iterable:
     sum += item
   return sum

Notice that this is not limited to summing ints, nor to summing values 
in a hash. sum(somedic.values()) does the specific task of summing hash 
values.

> Any time you use a GUI library, you can often use its own async
> primitives (in fact you probably need to).  For example glib from Gtk+
> provides io wait primitives.  Or if you want a completely asynchronous
> programming experience from top to bottom, you can use python twisted.
> There are also other libraries to do this.
>
> Having first-class language support is certainly nice, and it would be
> nice if Python had this.  GvR himself agrees.
> http://www.youtube.com/watch?v=sOQLVm0-8Yg

C#'s await was part of the early discussion about Python's new asynch 
library. Last I knew, 'Tulip' uses callbacks at the lowest level, but 
the user level uses generators and 'yield from'. I hope this makes in 
into 3.4.

-- 
Terry Jan Reedy