Wednesday, 5 May 2010

QTreeView and QAbractItemModel example

This little example sets up a pythonic model, attaches a treeview to it, and allows user interaction in 2 ways.

1. clicking on the treeview
2. making selections using buttons.

Why is this important? Well, "models" are not aware of what is selected by the various views attached to them. With multiple views of the same data (or related data) it is up to the coder to keep this reference. the button click stuff is used in this example to explore such a scenario.

from PyQt4 import QtGui, QtCore

HORIZONTAL_HEADERS = ("Surname", "Given Name")
class person_class(object):
    a trivial custom data object
    def __init__(self, sname, fname, isMale):
        self.sname = sname
        self.fname = fname
        self.isMale = isMale

    def __repr__(self):
        return "PERSON - %s %s"% (self.fname, self.sname)
class TreeItem(object):
    a python object used to return row/column data, and keep note of
    it's parents and/or children
    def __init__(self, person, header, parentItem):
        self.person = person
        self.parentItem = parentItem
        self.header = header
        self.childItems = []

    def appendChild(self, item):

    def child(self, row):
        return self.childItems[row]

    def childCount(self):
        return len(self.childItems)

    def columnCount(self):
        return 2
    def data(self, column):
        if self.person == None:
            if column == 0:
                return QtCore.QVariant(self.header)
            if column == 1:
                return QtCore.QVariant("")                
            if column == 0:
                return QtCore.QVariant(self.person.sname)
            if column == 1:
                return QtCore.QVariant(self.person.fname)
        return QtCore.QVariant()

    def parent(self):
        return self.parentItem
    def row(self):
        if self.parentItem:
            return self.parentItem.childItems.index(self)
        return 0

class treeModel(QtCore.QAbstractItemModel):
    a model to display a few names, ordered by sex
    def __init__(self, parent=None):
        super(treeModel, self).__init__(parent)
        self.people = []
        for fname, sname, isMale in (("John","Brown", 1), 
        ("Fred", "Bloggs", 1), ("Sue", "Smith", 0)):
            person = person_class(sname, fname, isMale)
        self.rootItem = TreeItem(None, "ALL", None)
        self.parents = {0 : self.rootItem}

    def columnCount(self, parent=None):
        if parent and parent.isValid():
            return parent.internalPointer().columnCount()
            return len(HORIZONTAL_HEADERS)

    def data(self, index, role):
        if not index.isValid():
            return QtCore.QVariant()

        item = index.internalPointer()
        if role == QtCore.Qt.DisplayRole:
        if role == QtCore.Qt.UserRole:
            if item:
                return item.person

        return QtCore.QVariant()

    def headerData(self, column, orientation, role):
        if (orientation == QtCore.Qt.Horizontal and
        role == QtCore.Qt.DisplayRole):
                return QtCore.QVariant(HORIZONTAL_HEADERS[column])
            except IndexError:

        return QtCore.QVariant()

    def index(self, row, column, parent):
        if not self.hasIndex(row, column, parent):
            return QtCore.QModelIndex()

        if not parent.isValid():
            parentItem = self.rootItem
            parentItem = parent.internalPointer()

        childItem = parentItem.child(row)
        if childItem:
            return self.createIndex(row, column, childItem)
            return QtCore.QModelIndex()

    def parent(self, index):
        if not index.isValid():
            return QtCore.QModelIndex()

        childItem = index.internalPointer()
        if not childItem:
            return QtCore.QModelIndex()
        parentItem = childItem.parent()

        if parentItem == self.rootItem:
            return QtCore.QModelIndex()

        return self.createIndex(parentItem.row(), 0, parentItem)

    def rowCount(self, parent=QtCore.QModelIndex()):
        if parent.column() > 0:
            return 0
        if not parent.isValid():
            p_Item = self.rootItem
            p_Item = parent.internalPointer()
        return p_Item.childCount()
    def setupModelData(self):
        for person in self.people:
            if person.isMale:
                sex = "MALES"
                sex = "FEMALES"
            if not self.parents.has_key(sex):                
                newparent = TreeItem(None, sex, self.rootItem)

                self.parents[sex] = newparent

            parentItem = self.parents[sex]
            newItem = TreeItem(person, "", parentItem)
    def searchModel(self, person):
        get the modelIndex for a given appointment
        def searchNode(node):
            a function called recursively, looking at all nodes beneath node
            for child in node.childItems:
                if person == child.person:
                    index = self.createIndex(child.row(), 0, child)
                    return index
                if child.childCount() > 0:
                    result = searchNode(child)
                    if result:
                        return result
        retarg = searchNode(self.parents[0])
        print retarg
        return retarg
    def find_GivenName(self, fname):
        app = None
        for person in self.people:
            if person.fname == fname:
                app = person
        if app != None:
            index = self.searchModel(app)
            return (True, index)            
        return (False, None)

if __name__ == "__main__":    

    def row_clicked(index):
        when a row is clicked... show the name
        print tv.model().data(index, QtCore.Qt.UserRole)
    def but_clicked():
        when a name button is clicked, I iterate over the model, 
        find the person with this name, and set the treeviews current item
        name = dialog.sender().text()
        print "BUTTON CLICKED:", name
        result, index = model.find_GivenName(name)
        if result:
            if index:
    app = QtGui.QApplication([])
    model = treeModel()
    dialog = QtGui.QDialog()

    layout = QtGui.QVBoxLayout(dialog)

    tv = QtGui.QTreeView(dialog)
    label = QtGui.QLabel("Search for the following person")
    buts = []
    frame = QtGui.QFrame(dialog)
    layout2 = QtGui.QHBoxLayout(frame)
    for person in model.people:
        but = QtGui.QPushButton(person.fname, frame)
        QtCore.QObject.connect(but, QtCore.SIGNAL("clicked()"), but_clicked)

    but = QtGui.QPushButton("Clear Selection")
    QtCore.QObject.connect(but, QtCore.SIGNAL("clicked()"), tv.clearSelection)

    QtCore.QObject.connect(tv, QtCore.SIGNAL("clicked (QModelIndex)"),




Geet said...


This was really useful, thanks!

Björn said...

Nice post, thanks for sharing!

emil said...

I'm trying to make this work with PySide, and python 3.2.

Replacing QVariant() with None and QVariant(x) with x gets pretty far, but still problem when clicking the search buttons, which gets the error:

"NoneType object has no attribute 'text' "
Traceback: name= dialog.sender().text()

any suggestions where the problem is?


Nam said...

very nice!

Raymond Wood said...

Reqarding emil's query about "NoneType object has no attribute 'text'" error:

Trying to use CObject.sender() with PySide can be problematic. For more details:

But, be advised, I ran into issues trying to use the approach mentioned on that page [which is to create a CObject subclass and then call sender() from that.

I got it to work with PySide and python v2.7 by using an approach that uses CSignalMapper:

san said...

what is the use of having buts = [] and appending buttons to that list you are not using it anyway further in the code.

邓凌煊 said...

very useful, there aren't many clear tutorials/demos like this around

Mike Bourbeau said...

Perfect, thanks!

boris runakov said...

I am running this from PyCharm 2016 Community edition and I am getting this error when closing the application :
QObject::startTimer: QTimer can only be used with threads started with QThread

Any feedback on this ?
Thank you !