[PyQt] Fast selection of non-contiguous items in QTreeview

[Bjorn Egil Ludvigsen]

I am planning similar things and will run into the same issue as you I
suspect. My benchmark will be a table model with up to 1 million rows. Each
of the rows may have 1,000 items (columns) and I need filter features to
select rows (numerical simulations). Related to this and Darryl's question,
would someone like to comment in general on the feasibility of using PyQt
for such large table models (or tree models etc.) and the maximum
responsiveness one can achieve?

Regards,
Bjorn

On Thu, Apr 8, 2010 at 3:14 PM, Darryl Wallace
<darryl.wallace at prosensus.ca>wrote:

>  *Here’s an example of the code:*
>
> * *
>
> *def searchAndSelect(self, searchString, column=0):*
>
> *    #If the user searches for nothing, then return and do nothing*
>
> *    if len(searchString)==0:*
>
> *        return*
>
> * *
>
> *    #get the selection model from the tree view*
>
> *    selectionModel=self.obsTreeView.selectionModel()*
>
> *  *
>
> *    # Find the items in the model.*
>
> *    # obsTreeModel is a QStandardItemModel*
>
> *    # This part is very fast *
>
> *    items=self.obsTreeModel.findItems(searchString,
> QtCore.Qt.MatchContains, column)*
>
> *    *
>
> *    #select each item*
>
> *    # This part is very slow.*
>
> *    for item in items:*
>
> *        selectionModel.select(item.index(),
> selectionModel.Select|selectionModel.Rows)*
>
> *#searchAndSelect*
>
> * *
>
> *Does anyone have any tips on speeding up the selection part?  I’ve tried
> blocking the signals of the selection model incase the selectionChanged
> signal of QItemSelectionModel is causing a re-draw but it didn’t seem to
> help.*
>
> * *
>
> *Thanks,
> Darryl*
>
>
>
> *From:* Darryl Wallace [mailto:darryl.wallace at prosensus.ca]
> *Sent:* April-08-10 2:23 PM
> *To:* 'pyqt at riverbankcomputing.com'
> *Subject:* Fast selection of non-contiguous items in QTreeview
>
>
>
> Hello,
>
>
>
> I’ve done some reading and can’t find anything on non-contiguous selection
> of items in item views beyond :
>
>
>
> “Selections are made up of *selection ranges*. These efficiently maintain
> information about large selections of items by recording only the starting
> and ending model indexes for each range of selected items. Non-contiguous
> selections of items are constructed by using more than one selection range
> to describe the selection.” -
> http://doc.trolltech.com/4.6/model-view-selection.html#concepts
>
>
>
> Currently we have implemented a selection of items by scanning each row in
> the model to see if it should be “selected” based on certain criteria.  Is
> there a faster way to do this as looping in Python through a large (50,000
> rows)?  When selections can be specified with selection ranges the selection
> is fast.  However, our worst case scenario is that every-other item need be
> selected: 25,000 selection ranges would be created and then we would just be
> looping through everything again anyways.
>
>
>
> Any ideas?
>
>
>
> Thanks,
>
> Darryl
>
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