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Date: Thu, 11 Dec 2014 23:07:22 -0700
From: Michael Torrie <torriem@gmail.com>
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Subject: Re: PyQt: user interface freezed when using concurrent.futures.ThreadPoolExecutor
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On 12/11/2014 08:20 PM, iMath wrote:
> 在 2014年12月11日星期四UTC+8下午1时25分41秒，Michael Torrie写道：
>> On 12/10/2014 09:52 PM, iMath wrote:
> "when it comes to I/O and GUIs, asynchronous calls are always better than threads."
> 
> I cannot grasp your meaning here, IMO, asynchronous calls are done by using threads.

Not in your code.  All your I/O calls are synchronous; they block until
they are finished.  But if you mean that calling synchronous calls while
in a thread has a similar effect to an asynchronous call, you are
correct.  But the way you're waiting for the threads to finish, you're
blocking your gui.

An asynchronous API lets you start long-running I/O calls and define a
function that is automatically called upon completion.  In other words
it's event-driven.  Qt may provide everything you need already in an
asynchronous form.  Check the docs. And use google.  Here's a link I
found from a google search that illustrates how to fetch a url in Qt
using an asynchronous method.  You could fire off as many of these as
you want, then just wait for signals.

http://qt-project.org/wiki/Download_Data_from_URL