Re: get duplicate frames when doing multiprocessing

I’m not sure that this book is in the public domain. Robin, can you comment?

> On Apr 5, 2021, at 1:04 PM, Nick Adams <[email protected]> wrote:
> 
> I agree with Matt, use threads. This book has helped me here.
> https://theswissbay.ch/pdf/Gentoomen%20Library/Programming/Python/wxPython%20in%20Action%20%282006%29.pdf <https://theswissbay.ch/pdf/Gentoomen%20Library/Programming/Python/wxPython%20in%20Action%20%282006%29.pdf>
> 
> see chapter 18 page 541 
> 
> On Mon, Apr 5, 2021 at 8:57 AM Matt Newville <[email protected] <mailto:[email protected]>> wrote:
> For I/O bound tasks such as reading from disk, use threads.
> 
> On Mon, Apr 5, 2021, 7:35 AM Yodash <[email protected] <>> wrote:
> first, thanks for the quick replay :)..
> my target is to load data frames in parallel in order to save time (trigger for the action is button click on frame)
> you are correct, i loaded same df 3 times but its just an example (on my production app they are not the same) 
> 
> the issue is that whenever I try to perform parallelism using multiprocessing..my frame is duplicated as number of child processes I declare 
> 
> it will be a pity not to be able use parallelism from wx...
> Sure I'm missing something
> 
> thanks,Yodash
> On Sunday, April 4, 2021 at 10:08:43 PM UTC+3 Tim Roberts wrote:
> On 4/4/21 9:39 AM, Yodash wrote:
> 
>> Hello
>> i'm trying to speed up my data load from pandas dataframe using multiprocessing
> 
> I can't tell what you were trying to achieve here.  Your code loads the same file in three different processes but then does nothing with it.  Each process will load the entire file.
> 
> Multiprocessing is really only useful in very limited circumstances.  Remember that, when you use multiprocessing, you are literally running different processes with different memory spaces.  They are not connected in any way.  You can feed data in and copy data back out at the end.  And, of course, you can only manipulate the UI in your main process.  None of the others have any UI.
> 
> IF you are trying to load a single dataframe by splitting the load across three processes, that's impossible.
> 
> 
>> my problem is that when i do multiprocessing from wx.frame , I surprisingly get duplicates of my frame - as the number of processes i'm trying to use  (no matter what method i use...Pool/Pool.apply_sync or Process(target=f_action,) 
>> 
>> it doesn't happen all the time
>> 
>> for example..this code will duplicate the frame 3 times:
> 
> The code you showed will certainly do that, because you're loading the same file 3 times.
> 
> --
> Tim Roberts, [email protected] <>
> Providenza & Boekelheide, Inc.
> 
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