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

[Darryl Wallace]

*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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