[wxPython-users] interest in DelayedResult?

[Robin Dunn]

Oliver Schoenborn wrote:
> I have created a module called DelayedResult.py (still prototype, but
> works) that helps use multithread in GUI apps, something many novice
> users are not comfortable with. It's basic use case is: 
> 
> - you have a task, triggered by a GUI event, that takes more than 
>   1/10th sec to execute, so you loose GUI response in that time
> - starting the task from the event handler actually involves going 
>   through one or more layers with pre-processing at each level; e.g. 
>   handler calls slowTask, which does some setup stuff then itself 
>   calls lowerLevelSlowTask, which starts the thread and returns
> immediately
> - when the task is done, the result is new data that must be pushed to
> the GUI 
> - once the result is available, each (or at least one) level needs to 
>   do some post-processing before the final result can be sent to GUI
> 
> DelayedResult makes it really easy to get the final result back from the
> thread to the GUI, without having to know anything about creating new
> event types or CallAfter etc. It manages the reverse chain of "callers",
> makes it a lot easier to transform a single thread impl to a
> multi-thread implementation, and makes it easy to see what is pre- and
> post-processing of the slow task. It also limits the amount of
> synchronization code needed. You need WxAppTester.py to run the module
> test. 

> Would it make sense to have it in wx.lib?
> 

Yes, I'm not sure I follow all of your explanation but I think that the 
concept is a good one.

BTW, the test code gets some exceptions:

$ py DelayedResult.py
Slow function started
Slow function done
Unhandled exception in thread started by <function slowFn at 0xb7d53064>
Traceback (most recent call last):
   File "DelayedResult.py", line 117, in slowFn
     cb.sendResult((5,'a'))
   File "DelayedResult.py", line 66, in sendResult
     print "Posting result (%s) to %s" % (self.peekResult(), fn0)
AttributeError: DelayedResult instance has no attribute 'peekResult'
Slow function started
Slow function done
Unhandled exception in thread started by <function slowFn at 0xb7d53064>
Traceback (most recent call last):
   File "DelayedResult.py", line 117, in slowFn
     cb.sendResult((5,'a'))
   File "DelayedResult.py", line 63, in sendResult
     fn0(self)
TypeError: __call__() takes exactly 3 arguments (2 given)

-- 
Robin Dunn
Software Craftsman
http://wxPython.org  Java give you jitters?  Relax with wxPython!