Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Newsgroups: comp.lang.python
Subject: Re: [Python-ideas] How the heck does async/await work in Python 3.5
Date: Wed, 24 Feb 2016 20:37:38 -0500
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On Thu, 25 Feb 2016 10:00:29 +1300, Gregory Ewing
<greg.ewing@canterbury.ac.nz> declaimed the following:

>?? wrote:
>> Suppose io_operation() takes 3 seconds, then how can I write something like
>> 
>> future = io_operation()
>> print('Start')
>> time.sleep(1)
>> print('Something')
>> time.sleep(2)
>> print(future.result())
>> 
>> that print 'Start' immediately and the result of io_operation() 3 seconds
>> later.
>
>Yes, Python can do this, but you probably need to use real
>threads. The only exception would be if io_operation() were
>something you could fire off with a single system call that's
>guaranteed not to block, and then wait for the result later.
>Opportunities for things like that are rare in unix.
>(Windows might be different, I'm not sure.)
>
	But was common under VMS
https://en.wikipedia.org/wiki/QIO

	I believe Windows is supposed to be similar, but QIO status words and
event flags were understandable to me (and close match to AmigaOS too <G>);
Windows somehow treats the I/O channel itself as the waitable object (well,
looks like one embeds it into the I/O call -- but has to create the channel
in "overlapped" mode where VMS differentiated on the I/O call itself: QIO
vs QIOW; Amiga differentiated with DoIO and SendIO)
https://msdn.microsoft.com/en-us/library/windows/desktop/ms686358%28v=vs.85%29.aspx

http://wiki.amigaos.net/wiki/Exec_Device_I/O#Synchronous_vs._Asynchronous_Requests
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/