Develop Reference

How to use an active QComboBox as an element of QListView in PyQt5?

I am using PyQt5 to make an application. One of my widgets will be a QListView that displays a list of required items, e.g. required to cook a particular dish, say.
For most of these, the listed item is the only possibility. But for a few items, there is more than one option that will fulfill the requirements. For those with multiple possibilities, I want to display those possibilities in a functional QComboBox. So if the user has no whole milk, they can click that item, and see that 2% milk also works.
How can I include working combo boxes among the elements of my QListView?
Below is an example that shows what I have so far. It can work in Spyder or using python -i, you just have to comment or uncomment as noted. By "work", I mean it shows the required items in QListView, but the combo boxes show only the first option, and their displays can't be changed with the mouse. However, I can say e.g. qb1.setCurrentIndex(1) at the python prompt, and then when I move the mouse pointer onto the widget, the display updates to "2% milk". I have found it helpful to be able to interact with and inspect the widget in Spyder or a python interpreter, but I still have this question. I know there are C++ examples of things like this around, but I have been unable to understand them well enough to do what I want. If we can post a working Python example of this, it will help me and others too I'm sure.
from PyQt5.QtWidgets import QApplication, QComboBox, QListView, QStyledItemDelegate
from PyQt5.QtCore import QAbstractListModel, Qt
# A delegate for the combo boxes.
class QBDelegate(QStyledItemDelegate):
def paint(self, painter, option, index):
painter.drawText(option.rect, Qt.AlignLeft, self.parent().currentText())
# my own wrapper for the abstract list class
class PlainList(QAbstractListModel):
def __init__(self, elements):
super().__init__()
self.elements = elements
def data(self, index, role):
if role == Qt.DisplayRole:
text = self.elements[index.row()]
return text
def rowCount(self, index):
try:
return len(self.elements)
except TypeError:
return self.elements.rowCount(index)
app = QApplication([]) # in Spyder, this seems unnecessary, but harmless.
qb0 = 'powdered sugar' # no other choice
qb1 = QComboBox()
qb1.setModel(PlainList(['whole milk','2% milk','half-and-half']))
d1 = QBDelegate(qb1)
qb1.setItemDelegate(d1)
qb2 = QComboBox()
qb2.setModel(PlainList(['butter', 'lard']))
d2 = QBDelegate(qb2)
qb2.setItemDelegate(d2)
qb3 = 'cayenne pepper' # there is no substitute
QV = QListView()
qlist = PlainList([qb0, qb1, qb2, qb3])
QV.setModel(qlist)
QV.setItemDelegateForRow(1, d1)
QV.setItemDelegateForRow(2, d2)
QV.show()
app.exec_() # Comment this line out, to run in Spyder. Then you can inspect QV etc in the iPython console. Handy!

There are some misconceptions in your attempt.
First of all, setting the delegate parent as a combo box and then setting the delegate for the list view won't make the delegate show the combo box.
Besides, as the documentation clearly says:
Warning: You should not share the same instance of a delegate between views. Doing so can cause incorrect or unintuitive editing behavior since each view connected to a given delegate may receive the closeEditor() signal, and attempt to access, modify or close an editor that has already been closed.
In any case, adding the combo box to the item list is certainly not an option: the view won't have anything to do with it, and overriding the data() to show the current combo item is not a valid solution; while theoretically item data can contain any kind of object, for your purpose the model should contain data, not widgets.
In order to show a different widget for a view, you must override createEditor() and return the appropriate widget.
Then, since you probably need to keep the data available when accessing the model and for the view, the model should contain the available options and eventually return the current option or the "sub-list" depending on the situation.
Finally, rowCount() must always return the row count of the model, not that of the content of the index.
A possibility is to create a "nested model" that supports a "current index" for the selected option for inner models.
Then you could either use openPersistentEditor() or implement flags() and add the Qt.ItemIsEditable for items that contain a list model.
class QBDelegate(QStyledItemDelegate):
def createEditor(self, parent, option, index):
value = index.data(Qt.EditRole)
if isinstance(value, PlainList):
editor = QComboBox(parent)
editor.setModel(value)
editor.setCurrentIndex(value.currentIndex)
# submit the data whenever the index changes
editor.currentIndexChanged.connect(
lambda: self.commitData.emit(editor))
else:
editor = super().createEditor(parent, option, index)
return editor
def setModelData(self, editor, model, index):
if isinstance(editor, QComboBox):
# the default implementation tries to set the text if the
# editor is a combobox, but we need to set the index
model.setData(index, editor.currentIndex())
else:
super().setModelData(editor, model, index)
class PlainList(QAbstractListModel):
currentIndex = 0
def __init__(self, elements):
super().__init__()
self.elements = []
for element in elements:
if isinstance(element, (tuple, list)) and element:
element = PlainList(element)
self.elements.append(element)
def data(self, index, role=Qt.DisplayRole):
if role == Qt.EditRole:
return self.elements[index.row()]
elif role == Qt.DisplayRole:
value = self.elements[index.row()]
if isinstance(value, PlainList):
return value.elements[value.currentIndex]
else:
return value
def flags(self, index):
flags = super().flags(index)
if isinstance(index.data(Qt.EditRole), PlainList):
flags |= Qt.ItemIsEditable
return flags
def setData(self, index, value, role=Qt.EditRole):
if role == Qt.EditRole:
item = self.elements[index.row()]
if isinstance(item, PlainList):
item.currentIndex = value
else:
self.elements[index.row()] = value
return True
def rowCount(self, parent=None):
return len(self.elements)
app = QApplication([])
qb0 = 'powdered sugar' # no other choice
qb1 = ['whole milk','2% milk','half-and-half']
qb2 = ['butter', 'lard']
qb3 = 'cayenne pepper' # there is no substitute
QV = QListView()
qlist = PlainList([qb0, qb1, qb2, qb3])
QV.setModel(qlist)
QV.setItemDelegate(QBDelegate(QV))
## to always display the combo:
#for i in range(qlist.rowCount()):
# index = qlist.index(i)
# if index.flags() & Qt.ItemIsEditable:
# QV.openPersistentEditor(index)
QV.show()
app.exec_()

Checkbox with persistent editor

I'm using a table to control the visibility and color of a plot. I would like a checkbox to toggle visibility and a drop-down to select the color. To this end, I have something like the following. It feels as through having a persistent editor prevents use of the checkbox.
The example is a bit contrived (in how the model/view are set up), but illustrates how the checkbox doesn't function while the editor is open.
How can I have a checkbox that can be used alongside a visible combobox? Is it better to use two columns?
import sys
from PyQt5 import QtWidgets, QtCore
class ComboDelegate(QtWidgets.QItemDelegate):
def __init__(self, parent):
super().__init__(parent=parent)
def createEditor(self, parent, option, index):
combo = QtWidgets.QComboBox(parent)
li = []
li.append("Red")
li.append("Green")
li.append("Blue")
li.append("Yellow")
li.append("Purple")
li.append("Orange")
combo.addItems(li)
combo.currentIndexChanged.connect(self.currentIndexChanged)
return combo
def setEditorData(self, editor, index):
editor.blockSignals(True)
data = index.model().data(index)
if data:
idx = int(data)
else:
idx = 0
editor.setCurrentIndex(0)
editor.blockSignals(False)
def setModelData(self, editor, model, index):
model.setData(index, editor.currentIndex())
#QtCore.pyqtSlot()
def currentIndexChanged(self):
self.commitData.emit(self.sender())
class PersistentEditorTableView(QtWidgets.QTableView):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
QtCore.pyqtSlot('QVariant', 'QVariant')
def data_changed(self, top_left, bottom_right):
for row in range(len(self.model().tableData)):
self.openPersistentEditor(self.model().index(row, 0))
class TableModel(QtCore.QAbstractTableModel):
def __init__(self, parent=None):
super(TableModel, self).__init__(parent)
self.tableData = [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
self.checks = {}
def columnCount(self, *args):
return 3
def rowCount(self, *args):
return 3
def checkState(self, index):
if index in self.checks.keys():
return self.checks[index]
else:
return QtCore.Qt.Unchecked
def data(self, index, role=QtCore.Qt.DisplayRole):
row = index.row()
col = index.column()
if role == QtCore.Qt.DisplayRole:
return '{0}'.format(self.tableData[row][col])
elif role == QtCore.Qt.CheckStateRole and col == 0:
return self.checkState(QtCore.QPersistentModelIndex(index))
return None
def setData(self, index, value, role=QtCore.Qt.EditRole):
if not index.isValid():
return False
if role == QtCore.Qt.CheckStateRole:
self.checks[QtCore.QPersistentModelIndex(index)] = value
self.dataChanged.emit(index, index)
return True
return False
def flags(self, index):
fl = QtCore.QAbstractTableModel.flags(self, index)
if index.column() == 0:
fl |= QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsUserCheckable
return fl
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
view = PersistentEditorTableView()
view.setItemDelegateForColumn(0, ComboDelegate(view))
model = TableModel()
view.setModel(model)
model.dataChanged.connect(view.data_changed)
model.layoutChanged.connect(view.data_changed)
index = model.createIndex(0, 0)
persistet_index = QtCore.QPersistentModelIndex(index)
model.checks[persistet_index] = QtCore.Qt.Checked
view.data_changed(index, index)
view.show()
sys.exit(app.exec_())

NOTE: After some rethinking and analysis of the Qt source code, I realized that my original answer, while valid, is a bit imprecise.
The problem relies on the fact that all events received on an index with an active editor are automatically sent to the editor, but since the editor could have a geometry that is smaller than the visual rect of the index, if a mouse event is sent outside the geometry that event is ignored and not processed by the view as it normally would without an editor.
UPDATE: In fact, the view does receive the event; the problem is that if an editor exists the event is automatically ignored furtherward (since it's assumed that the editor handled it) and nothing is sent to the editorEvent method of the delegate.
You can intercept "mouse edit" events as long as you implement the virtual edit(index, trigger, event) function (which is not the same as the edit(index) slot). Note that this means that if you override that function, you cannot call the default edit(index) anymore, unless you create a separate function that calls the default implementation (via super().edit(index)).
Consider that the following code works better if the delegate is actually a QStyledItemDelegate, instead of the simpler QItemDelegate class: the Qt dev team itself suggests to use the styled class instead of the basic one (which is intended for very basic or specific usage), as it's generally considered more consistent.
class PersistentEditorTableView(QtWidgets.QTableView):
# ...
def edit(self, index, trigger, event):
# if the edit involves an index change, there's no event
if (event and index.column() == 0 and
index.flags() & QtCore.Qt.ItemIsUserCheckable and
event.type() in (event.MouseButtonPress, event.MouseButtonDblClick) and
event.button() == QtCore.Qt.LeftButton):
opt = self.viewOptions()
opt.rect = self.visualRect(index)
opt.features |= opt.HasCheckIndicator
checkRect = self.style().subElementRect(
QtWidgets.QStyle.SE_ItemViewItemCheckIndicator,
opt, self)
if event.pos() in checkRect:
if index.data(QtCore.Qt.CheckStateRole):
state = QtCore.Qt.Unchecked
else:
state = QtCore.Qt.Checked
return self.model().setData(
index, state, QtCore.Qt.CheckStateRole)
return super().edit(index, trigger, event)
Obviously, you could do something similar by implementing the mousePressEvent on the view, but that could complicate things if you need some different implementation of the mouse press event also, and you should also consider the double click events. Implementing edit() is conceptually better, since it's more consistent with the purpose: clicking -> toggling.
There's only one last catch: keyboard events.
A persistent editor automatically grabs the keyboard focus, so you can't use any key (usually, the space bar) to toggle the state if the editor handles that event; since a combobox handles some "toggle" events to show its popup, those events won't be received by the view (the focus is on the combo, not on the view!) unless you ignore the event by properly implementing the eventFilter of the delegate for both keyboard events and focus changes.
Original answer
There are various possibilities to work around this:
as you proposed, use a separate column; this is not always possible or suggested, as the model structure could not allow it;
create an editor that also includes a QCheckBox; as long as there will always be an open editor, this is not an issue, but could create some level of inconsistency if editor could actually be open and destroyed;
add the combo to a container that has a fixed margin, so that mouse event not handled by the combo can be captured by the delegate event filter;
The third possibility is a bit more complex, but it ensures that both displaying and interaction are consistent with the normal behavior.
To achieve this, using a QStyledItemDelegate is suggested as it provides access to the style options.
class ComboDelegate(QtWidgets.QStyledItemDelegate):
# ...
def createEditor(self, parent, option, index):
option = QtWidgets.QStyleOptionViewItem(option)
self.initStyleOption(option, index)
style = option.widget.style()
textRect = style.subElementRect(
style.SE_ItemViewItemText, option, option.widget)
editor = QtWidgets.QWidget(parent)
editor.index = QtCore.QPersistentModelIndex(index)
layout = QtWidgets.QHBoxLayout(editor)
layout.setContentsMargins(textRect.left(), 0, 0, 0)
editor.combo = QtWidgets.QComboBox()
layout.addWidget(editor.combo)
editor.combo.addItems(
("Red", "Green", "Blue", "Yellow", "Purple", "Orange"))
editor.combo.currentIndexChanged.connect(self.currentIndexChanged)
return editor
def setEditorData(self, editor, index):
editor.combo.blockSignals(True)
data = index.model().data(index)
if data:
idx = int(data)
else:
idx = 0
editor.combo.setCurrentIndex(0)
editor.combo.blockSignals(False)
def eventFilter(self, editor, event):
if (event.type() in (event.MouseButtonPress, event.MouseButtonDblClick)
and event.button() == QtCore.Qt.LeftButton):
style = editor.style()
size = style.pixelMetric(style.PM_IndicatorWidth)
left = editor.layout().contentsMargins().left()
r = QtCore.QRect(
(left - size) / 2,
(editor.height() - size) / 2,
size, size)
if event.pos() in r:
model = editor.index.model()
index = QtCore.QModelIndex(editor.index)
if model.data(index, QtCore.Qt.CheckStateRole):
value = QtCore.Qt.Unchecked
else:
value = QtCore.Qt.Checked
model.setData(
index, value, QtCore.Qt.CheckStateRole)
return True
return super().eventFilter(editor, event)
def updateEditorGeometry(self, editor, opt, index):
# ensure that the editor fills the whole index rect
editor.setGeometry(opt.rect)
Unrelated, but still important:
Consider that the #pyqtSlot decorator is usually not required in normal situations like these. Also note that you missed the # for the data_changed decorator, and the signature is also invalid, since it's incompatible with the signals you've connected it to. A more correct slot decoration would have been the following:
#QtCore.pyqtSlot(QtCore.QModelIndex, QtCore.QModelIndex, 'QVector<int>')
#QtCore.pyqtSlot('QList<QPersistentModelIndex>', QtCore.QAbstractItemModel.LayoutChangeHint)
def data_changed(self, top_left, bottom_right):
# ...
With the first decoration for the dataChanged signal, and the second for layoutChanged. But, as said before, it's generally unnecessary to use slots as they usually are only required for better threading handling and sometimes provide slightly improved performance (which is not that important to this purpose).
Also note that if you want to ensure that there's always an open editor whenever the model changes its "layout", you should also connect to rowsInserted and columnsInserted signals, since those operations do not send the layout change signal.

Dynamically add QTableView to dynamically created tab pages (QTabWidget)

I am trying to have a series of QTableView created at runtime and added to newly created pages of a multipage QTabWidget.
All seems to go fine, but the QTableView don't show up.
The QTabWidget gets zeroed (reset to no pages) and refurbished (...) flawlessly (at least it looks like so) depending on the selection of a combobox (and the dictionaries therein related).
I am also using a delegate callback to include a column of checkboxes to the QTableView (thanks to https://stackoverflow.com/a/50314085/7710452), which works fine stand alone.
Here is the code.
Main Window
EDIT
as recommended by eyllanesc, here is the standalone module (jump to the end of the post for details on the part I think is problematic):
"""
qt5 template
"""
import os
import sys
from PyQt5 import QtWidgets as qtw
from PyQt5 import QtCore as qtc
from PyQt5 import QtGui as qtg
from PyQt5 import uic
from configparser import ConfigParser, ExtendedInterpolation
from lib.SearchControllers import findGuis, get_controller_dict, show_critical, show_exception
import resources.resources
from lib.CheckBoxesDelegate import CheckBoxDelegate
myForm_2, baseClass = uic.loadUiType('./forms/setup.ui')
class MainWindow(baseClass):
def __init__(self, config_obj: ConfigParser,
config_name: str,
proj_name: str,
*args,
**kwargs):
super().__init__(*args, **kwargs)
self.ui = myForm_2()
self.ui.setupUi(self)
# your code begins here
self.setWindowTitle(proj_name + " Setup")
self.ui.logo_lbl.setPixmap(qtg.QPixmap(':/logo_Small.png'))
self.config_obj = config_obj
self.config_name = config_name
self.proj_filename = proj_name
self.proj_config = ConfigParser(interpolation=ExtendedInterpolation())
self.proj_config.read(proj_name)
self.guis_dict = {}
self.components = {}
self.cdp_signals = {}
self.root_path = self.config_obj['active']['controllers']
self.tableViews = []
self.tabs = []
self.iniControllersBox()
self.setActSignals()
self.load_bulk()
self.set_signals_table()
self.update_CurController_lbl()
self.update_ControllersTab() # here is where the action gets hot
# your code ends here
self.show() # here crashes if I passed the new tab to the instance of
# QTabView. otherwise it shows empty tabs
#########################################################
def load_bulk(self):
# get the list of running components into a dictionary
for i in self.list_controllers:
i_path = os.path.join(self.root_path, i)
print(i)
self.components[i] = get_controller_dict(i_path,
self.config_obj,
'Application.xml',
'Subcomponents/Subcomponent',
'Name',
'src')
for j in self.components[i]:
print(j)
signals_key = (i , j)
tgt = os.path.join(self.root_path, self.components[i][j])
self.cdp_signals[signals_key] = get_controller_dict(i_path,
self.config_obj,
self.components[i][j],
'Signals/Signal',
'Name',
'Type',
'Routing')
def set_signals_table(self):
self.ui.MonitoredDevicesTable.setHorizontalHeaderItem(0, qtw.QTableWidgetItem('GUI caption'))
self.ui.MonitoredDevicesTable.setHorizontalHeaderItem(1, qtw.QTableWidgetItem('Monitored Signal'))
def setActSignals(self):
self.ui.controllersBox.currentIndexChanged.connect(self.update_guis_list)
self.ui.controllersBox.currentIndexChanged.connect(self.update_CurController_lbl)
self.ui.controllersBox.currentIndexChanged.connect(self.update_ControllersTab)
def update_ControllersTab(self):
self.ui.componentsTab.clear() # this is the QTabWidget
self.tabs = []
self.tableViews = []
curr_controller = self.ui.controllersBox.currentText()
for i in self.components[curr_controller]:
if len(self.cdp_signals[curr_controller, i]) == 0:
continue
self.tabs.append(qtw.QWidget())
tabs_index = len(self.tabs) - 1
header_labels = ['', 'Signal', 'Type', 'Routing', 'Input']
model = qtg.QStandardItemModel(len(self.cdp_signals[curr_controller, i]), 5)
model.setHorizontalHeaderLabels(header_labels)
# in the next line I try to create a new QTableView passing
# the last tab as parameter, in the attempt to embed the QTableView
# into the QWidget Tab
self.tableViews.append(qtw.QTableView(self.tabs[tabs_index]))
tbw_Index = len(self.tableViews) - 1
self.tableViews[tbw_Index].setModel(model)
delegate = CheckBoxDelegate(None)
self.tableViews[tbw_Index].setItemDelegateForColumn(0, delegate)
rowCount = 0
for row in self.cdp_signals[curr_controller, i]:
for col in range(len(self.cdp_signals[curr_controller, i][row])):
index = model.index(rowCount, col, qtc.QModelIndex())
model.setData(index, self.cdp_signals[curr_controller, i][row][col])
try:
self.ui.componentsTab.addTab(self.tabs[tabs_index], i) # no problems, some controllers ask up to
except Exception as ex:
print(ex)
def update_CurController_lbl(self):
self.ui.active_controller_lbl.setText(self.ui.controllersBox.currentText())
def iniControllersBox(self):
self.list_controllers = [os.path.basename(f.path) for f in os.scandir(self.root_path) if f.is_dir() and str(
f.path).upper().endswith('NC')]
self.ui.controllersBox.addItems(self.list_controllers)
for i in range(self.ui.controllersBox.count()):
self.ui.controllersBox.setCurrentIndex(i)
newKey = self.ui.controllersBox.currentText()
cur_cntrlr = os.path.join(self.config_obj['active']['controllers'], self.ui.controllersBox.currentText())
self.guis_dict[newKey] = findGuis(cur_cntrlr, self.config_obj)
self.ui.controllersBox.setCurrentIndex(0)
self.update_guis_list()
def update_guis_list(self, index=0):
self.ui.GuisListBox.clear()
self.ui.GuisListBox.addItems(self.guis_dict[self.ui.controllersBox.currentText()])
if __name__ == '__main__':
config = ConfigParser()
config.read('./config.ini')
app = qtw.QApplication([sys.argv])
w = MainWindow(config, './config.ini',
'./test_setup_1.proj')
sys.exit(app.exec_())
and here the external to add the checkboxes column:
class CheckBoxDelegate(QtWidgets.QItemDelegate):
"""
A delegate that places a fully functioning QCheckBox cell of the column to which it's applied.
"""
def __init__(self, parent):
QtWidgets.QItemDelegate.__init__(self, parent)
def createEditor(self, parent, option, index):
"""
Important, otherwise an editor is created if the user clicks in this cell.
"""
return None
def paint(self, painter, option, index):
"""
Paint a checkbox without the label.
"""
self.drawCheck(painter, option, option.rect, QtCore.Qt.Unchecked if int(index.data()) == 0 else QtCore.Qt.Checked)
def editorEvent(self, event, model, option, index):
'''
Change the data in the model and the state of the checkbox
if the user presses the left mousebutton and this cell is editable. Otherwise do nothing.
'''
if not int(index.flags() & QtCore.Qt.ItemIsEditable) > 0:
return False
if event.type() == QtCore.QEvent.MouseButtonRelease and event.button() == QtCore.Qt.LeftButton:
# Change the checkbox-state
self.setModelData(None, model, index)
return True
if event.type() == QtCore.QEvent.MouseButtonPress or event.type() == QtCore.QEvent.MouseMove:
return False
return False
def setModelData (self, editor, model, index):
'''
The user wanted to change the old state in the opposite.
'''
model.setData(index, 1 if int(index.data()) == 0 else 0, QtCore.Qt.EditRole)
The 1st picture shows the layout in QTDesigner, the 2nd the result (emtpy tabs) when avoiding the crashing.
the QTabWidget has no problems in zeroing, or scale up, back to as many tab as I need, it's just that I have no clue on how to show the QTabview. My approach was to try to embed the QTabView in the tabpage passing it as parameter to the line creating the new QTabView.
Since I am using rather convoluted dictionaries, calling an XML parser to fill them up, not to mention the config files, I know even this version of my script is hardly reproduceable/runnable.
If someone had the patience of focusing on the update_ControllersTab method though, and tell me what I am doing wrong handling the QWidgets, it'd be great.
Again the basic idea is to clear the QTabWidget any time the user selects a different controller (combo box on the left):
self.ui.componentsTab.clear() # this is the QTabWidget
self.tabs = [] # list to hold QTabView QWidgets (pages) throughout the scope
self.tableViews = [] # list to hold QTabView(s) thorughout the scope
count how many tabs (pages) and hence embedded TabViews I need with the new controllers selected.
and then for each tab needed:
create a new tab (page)
self.tabs.append(qtw.QWidget())
tabs_index = len(self.tabs) - 1
create a new QTabView using a model:
header_labels = ['', 'Signal', 'Type', 'Routing', 'Input']
model = qtg.QStandardItemModel(len(self.cdp_signals[curr_controller, i]), 5)
model.setHorizontalHeaderLabels(header_labels)
self.tableViews.append(qtw.QTableView(self.tabs[tabs_index]))
tbw_Index = len(self.tableViews) - 1
self.tableViews[tbw_Index].setModel(model)
populate the TableView with data, and then finally add the tab widget (with the suppposedly embedded QTableView to the QTabWidget (the i argument is a string from my dbases Names:
self.ui.componentsTab.addTab(self.tabs[tabs_index], i)
This method is called also by the __init__ to initialize and apparently all goes error free, until the last 'init' statement:
`self.show()`
at which point the app crashes with:
Process finished with exit code 1073741845
on the other hand, if here instead of trying to embed the QTableView:
self.tableViews.append(qtw.QTableView(self.tabs[tabs_index]))
I omit the parameter, that is:
self.tableViews.append(qtw.QTableView())
the app doesn't crash anymore, but of course no QtableViews are shown, only empty tabpages:

As stupid as this may sound the problem is in... the delegate class that creates the checkboxes in the first column (see https://stackoverflow.com/a/50314085/7710452)
I commented out those two lines:
delegate = CheckBoxDelegate(None)
self.tableViews[tbw_Index].setItemDelegateForColumn(0, delegate)
and... bingo!
the CheckBoxDelegate works fine in the example shown in the post (a single QTableView form). I also tinkered around adding columns and rows, and moving the checkbox column back and forth with no problems. In that standalone. But as soon as I add the class and set the delegate, i am back at square zero, app crashing with:
Process finished with exit code 1073741845
so I am left with this problem now. Thnx to whomever read this.

Problem solved, see comment to post above.

Qt Drag & Drop doesn't work fine with custom items

I'm building a GUI using PySide2 (Qt5) with a custom treeview widget (MyTreeView, inherited from QTreeView). The model is a QStandardItemModel object whereas the items are custom: MyStandardItem, inherited from QStandardItem.
The problem is: if I check the type of the moved item after a drag and drop action, it has become a QStandardItem but it should have been a MyStandardItem.
I believe that the problem is the MimeType, and after a lot of research I found out that the solution could be creating a custom model and overriding MIME related functions.
I tried to figure out how but I couldn't.
So, here are the questions:
Do I have to create a custom model or is there a simple solution?
If I have to create a custom model, which functions should I override and how should I override those functions?
For what it's worth, here is MyStandardItem implementation:
class MyStandardItem(QStandardItem):
def __init__(self, text, font, icon_path='', value='', num=0, check_state=None):
super().__init__()
self.setDragEnabled(True)
self.setDropEnabled(True)
self.setText(text)
self.setData({'value': (value, num)})
self.setToolTip(str(self.data()['value']))
self.setFont(font)
self.setIcon(QIcon(icon_path))
self.toggled = check_state
if check_state is not None:
self.setCheckable(True)
self.setCheckState(check_state)
def setCheckState(self, checkState):
super().setCheckState(checkState)
if checkState == Qt.Unchecked:
self.toggled = Qt.Unchecked
else:
self.toggled = Qt.Checked

I found a way to solve this problem without having to create a custom model.
In the MyTreeView.dropEvent function: I dont't call super().dropEvent() to complete the drag&drop action but I implement it by myself by copying item's data in a variable and creating a new MyStandardItem from those data. Then I call insertRow() to insert the new item in the given position and deleteRow() to delete the old item.
Clearly, the moved item has to be stored in a class attribute at the beginning of the action (DragEnterEvent()).
Everything works perfectly.
PS: I've already tried this way before but I always ended up by having an empty row. The difference here is that I create a new item instead of re-inserting the old one.
Here's some parts of my code to clarify what I mean. Please, note that these functions are MyTreeView's methods.
def dragEnterEvent(self, event: QDragEnterEvent):
if event.source() == self:
self.dragged_item = self.model.itemFromIndex(self.selectionModel().selectedIndexes()[0])
super().dragEnterEvent(event)
else:
...
def dropEvent(self, event: QDropEvent):
index = self.indexAt(event.pos())
if not index.isValid():
return
over_item = self.model.itemFromIndex(index)
over_value = over_item.data()['value'][0]
if event.source() == self:
item_was_moved = self._move_item(over_value, over_parent_value)
if not item_was_moved:
return
else:
...
def _move_item(self, over_value, over_parent_value):
over_value = self._check_indicator_position(over_value)
if over_value is None:
return False
dragged_parent_value = self.dragged_item.parent().data()['value'][0]
dragged_value = self.dragged_item.data()['value'][0]
row = self.dragged_item.row()
items = guifunc.copy_row_items(self.dragged_item, row)
over_value_num = int(over_value.strip('test'))
self.dragged_item.parent().insertRow(over_value_num, items)
if over_value_num < row:
row += 1
self.dragged_item.parent().removeRow(row)
return True

Tracking checked items in QTreeWidget when loading in new set of data

I have a QTreeWidget in my gui in which the contents will be cleared whenever it loads in a different set of data and I am trying to tracked what has been checked as User loads in different data set.
Initially, I thought of tracking it using derive_tree_items method that I created in which it contains the QTreeWidgetItem object, however as soon as I tried to load in a new set of data, the objects that I stored will be lost as they are deleted (expected)..
Currently at a lost what is a better way to 'track' these checkable items? (I may also need to populate them into QMenu + QAction, hence the trackable checking but that will be for next time)
In my code, you can replicate by:
Click on button 'Data-01'
Check any objects, eg. I checked 'c102' and 'a102'
Click on button 'Data-02'
Click on button 'Data-01' again
Expecting to see 'c102', 'a102' is checked..
IsNewItemRole = QtCore.Qt.UserRole + 1000
class CustomTreeWidgetItem(QtGui.QTreeWidgetItem):
"""Initialization class for QTreeWidgetItem creation.
Args:
widget (QtGui.QTreeWidget): To append items into.
text (str): Input name for QTreeWidgetItem.
is_tristate (bool): Should it be a tri-state checkbox. False by default.
"""
def __init__(self, parent=None, text=None, is_tristate=False, is_new_item=False):
super(CustomTreeWidgetItem, self).__init__(parent)
self.setText(0, text)
# flags = QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsUserCheckable
if is_tristate:
# flags |= QtCore.Qt.ItemIsTristate
# Solely for the Parent item
self.setFlags(
self.flags()
| QtCore.Qt.ItemIsTristate
| QtCore.Qt.ItemIsEditable
| QtCore.Qt.ItemIsUserCheckable
)
else:
self.setFlags(
self.flags()
| QtCore.Qt.ItemIsEditable
| QtCore.Qt.ItemIsUserCheckable
)
self.setCheckState(0, QtCore.Qt.Unchecked)
self.setData(0, IsNewItemRole, is_new_item)
def setData(self, column, role, value):
"""Override QTreeWidgetItem setData function.
QTreeWidget does not have a signal that defines when an item has been
checked/ unchecked. And so, this method will emits the signal as a
means to handle this.
Args:
column (int): Column value of item.
role (int): Value of Qt.ItemDataRole. It will be Qt.DisplayRole or
Qt.CheckStateRole
value (int or unicode):
"""
state = self.checkState(column)
QtGui.QTreeWidgetItem.setData(self, column, role, value)
if (role == QtCore.Qt.CheckStateRole and
state != self.checkState(column)):
tree_widget = self.treeWidget()
if isinstance(tree_widget, CustomTreeWidget):
tree_widget.itemToggled.emit(self, column)
class CustomTreeWidget(QtGui.QTreeWidget):
"""Initialization class for QTreeWidget creation.
Args:
widget ():
"""
# itemToggled = QtCore.pyqtSignal(QtGui.QTreeWidgetItem, bool)
itemToggled = QtCore.Signal(QtGui.QTreeWidgetItem, bool)
contentUpdates = QtCore.Signal()
def __init__(self, widget=None):
super(CustomTreeWidget, self).__init__(widget)
self.rename_counter = False
# self.itemToggled.connect(self.handleItemToggled)
self.currentItemChanged.connect(self.selection_item_changed)
self.itemChanged.connect(self.tree_item_changed)
self.itemDoubleClicked.connect(self.tree_item_double_clicked)
def selection_item_changed(self, current, previous):
"""Overrides widget's default signal.
Emiited when current item selection is changed. This will also toggles
the state of `self.add_child_btn`.
If a child item is selected, the "Add Child" button will be disabled.
Args:
current (CustomTreeWidgetItem): Currently selected item.
previous (CustomTreeWidgetItem or None): Previous selected item.
"""
state = True
if not current or current.parent():
state = False
def tree_item_changed(self, item, column):
"""Overrides widget's default signal.
Emitted when the contents of the selected item in the column changes.
Args:
item (CustomTreeWidgetItem): Selected item.
column (int): Column value of the selected item.
"""
if self.rename_counter and self.prev_name != item.text(column):
self.rename_counter = False
item.setData(0, IsNewItemRole, True)
self.contentUpdates.emit()
elif item.checkState(column) == QtCore.Qt.Checked:
print('Item Checked')
elif item.checkState(column) == QtCore.Qt.Unchecked:
print('Item Unchecked')
def tree_item_double_clicked(self, item, column):
"""Overrides widget's default signal.
Emitted when User performs double clicks inside the widget.
Args:
item (CustomTreeWidgetItem): Selected item.
column (int): Column value of the selected item.
"""
self.prev_name = item.text(column)
self.rename_counter = True
def derive_tree_items(self, mode="all"):
all_items = OrderedDict()
root_item = self.invisibleRootItem()
top_level_count = root_item.childCount()
for i in range(top_level_count):
top_level_item = root_item.child(i)
top_level_item_name = str(top_level_item.text(0))
child_num = top_level_item.childCount()
all_items[top_level_item_name] = []
for n in range(child_num):
child_item = top_level_item.child(n)
child_item_name = str(child_item.text(0)) or ""
all_items[top_level_item_name].append(child_item)
return all_items
class MainApp(QtGui.QWidget):
def __init__(self, parent=None):
super(MainApp, self).__init__(parent)
self._diff_highlight = False
self._tree = CustomTreeWidget()
self._tree.header().hide()
# QTreeWidget default signals override
self._tree.contentUpdates.connect(self.update_dictionary)
tree_layout = QtGui.QVBoxLayout()
self.btn1 = QtGui.QPushButton("Data-01")
self.btn2 = QtGui.QPushButton("Data-02")
tree_layout.addWidget(self._tree)
tree_layout.addWidget(self.btn1)
tree_layout.addWidget(self.btn2)
main_layout = QtGui.QHBoxLayout()
main_layout.addLayout(tree_layout)
self.setLayout(main_layout)
self.setup_connections()
def setup_connections(self):
self.btn1.clicked.connect(self.show_data_01)
self.btn2.clicked.connect(self.show_data_02)
def update_dictionary(self):
print '>>> update: ', self._tree.derive_tree_items()
def show_data_01(self):
print '>>> Button1 test'
self._tree.clear()
test_dict1 = {
"itemA" :{
"menuA": ["a101", "a102"],
},
"itemBC": {
"menuC": ["c101", "c102", "c103"],
"menuB": ["b101"]
},
}
for page_name, page_contents in test_dict1.items():
# page_item = PageHeaderItem(self._tree, page_name)
for pk, pv in page_contents.items():
parent = CustomTreeWidgetItem(self._tree, pk, is_tristate=True)
for c in pv:
child = CustomTreeWidgetItem(parent, c)
self._tree.expandAll()
def show_data_02(self):
print '>>> Button2 test'
self._tree.clear()
test_dict2 = {
"itemD" :{
"menuD": ["d100"],
},
}
for page_name, page_contents in test_dict2.items():
# page_item = PageHeaderItem(self._tree, page_name)
for pk, pv in page_contents.items():
parent = CustomTreeWidgetItem(self._tree, pk, is_tristate=True)
for c in pv:
child = CustomTreeWidgetItem(parent, c)
self._tree.expandAll()
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
w = MainApp()
w.show()
sys.exit(app.exec_())

A QTreeWidget (like QListWidget and QTableWidget) has its internal model; it's some sort of a high-level access to a data model, and its actual model is not directly (as in easily) accessible, nor it should. They are "simplified" model-view interfaces, intended for general use that don't require advanced editing, but - most importantly - they only support their own, single and unique model. There's no easy way to change it except from their Q[viewType]WidgetItem interfaces, unless you completely reset the model, meaning that you'll need to "store" the data somewhere else if you want to use multiple models in the same view, making the whole thing much more complex than it needs to be and much prone to errors and issues, which is exactly what happens in your case.
On the opposite side, those QWidgetItemViews offer some features missing in standard models and views, and one of them is the "auto-check" of items in QTreeWidgets.
While that feature is very useful, it could be a serius PITA when you need to show different data models on the same view; this means that, to avoid the rhetorical reinvention of the wheel, it's better to stick with the QTreeView/QStandardItemModel pair and just implement the tristate mechanism instead of using convoluted methods that might clash with the internal implementation of a QTreeWidget.
Separate QStandardItemModel subclass instancies, with parent/child Tristate support
The most important aspect here is that you will be using a single data model class instance for each data set (instead of multiple dict + view's model pairs), making it much easier to switch between them with a simple flick of setModel().
The drawback is the aforementioned lack of parent/children state support, which has to be implemented; once that logic is solved, you'll get multiple persistent, unique and consistent models, no matter how many of them you actually need.
Besides the actual model contents initialization, you are only required to subclass two methods of QStandardItemModel:
setData(index, value, role) is overridden to apply the check state to the children indexes: if the role is Qt.CheckState and the index has any children, the [un]checked state is applied to them; if the index has a parent, the index emits the dataChanged signal to the model, ensuring that its view[s] requires updates (otherwise the checkbox visible state won't be updated correctly until the view is repainted)[1];
data(index, role) overriding is required to "show" the checkstate for the parent(s); it doesn't matter what the model's index data is: if it has any children, its state totally depends on them (all/any/none checked), otherwise it's based on the default model index's checkState;
Once that's solved, you only have to care about setting the newly selected model to the view, and all states will be there as they were before switching to another model, if any.
To keep some consistence with your example, I used your dict-based model data creation logic, but I'd suggest you to use a recursive method to add sub-children.
Since I was already there, I also added a mechanism to store the expanded state of every index, for better view/model consistency; it's not required, but it really helps user experience :-) Keep in mind that that's just there for demonstration purposes: obviously, if you add/remove items without taking care of the internal expandState dict, this won't work properly (or won't work at all!).
import sys
from PyQt5 import QtCore, QtGui, QtWidgets
dataSets = [
{
"itemA" :{
"menuA": ["a101", "a102"],
},
"itemBC": {
"menuC": ["c101", "c102", "c103"],
"menuB": ["b101"]
},
},
{
"itemD" :{
"menuD": ["d100"],
},
}
]
class TreeModel(QtGui.QStandardItemModel):
checkStateChange = QtCore.pyqtSignal(QtCore.QModelIndex, bool)
def __init__(self, dataSet):
super(TreeModel, self).__init__()
# unserialize data, as per your original code; you might want to use a
# recursive function instead, to allow multiple levels of items
for page_name, page_contents in dataSet.items():
for pk, pv in page_contents.items():
parent = QtGui.QStandardItem(pk)
parent.setCheckable(True)
self.appendRow(parent)
if pv:
parent.setTristate(True)
for c in pv:
child = QtGui.QStandardItem(c)
child.setCheckable(True)
parent.appendRow(child)
self.dataChanged.connect(self.checkStateChange)
def setData(self, index, value, role=QtCore.Qt.EditRole):
if role == QtCore.Qt.CheckStateRole:
childState = QtCore.Qt.Checked if value else QtCore.Qt.Unchecked
# set all children states according to this parent item
for row in range(self.rowCount(index)):
for col in range(self.columnCount(index)):
childIndex = self.index(row, col, index)
self.setData(childIndex, childState, QtCore.Qt.CheckStateRole)
# if the item has a parent, emit the dataChanged signal to ensure
# that the parent state is painted correctly according to what data()
# will return; note that this will emit the dataChanged signal whatever
# the "new" parent state is, meaning that it might still be the same
parent = self.parent(index)
if parent.isValid():
self.dataChanged.emit(parent, parent)
return super(TreeModel, self).setData(index, value, role)
def data(self, index, role=QtCore.Qt.DisplayRole):
# QStandardItemModel doesn't support auto tristate based on its children
# as it does for QTreeWidget's internal model; we have to implement that
if role == QtCore.Qt.CheckStateRole and self.flags(index) & QtCore.Qt.ItemIsTristate:
childStates = []
# collect all child check states
for row in range(self.rowCount(index)):
for col in range(self.columnCount(index)):
childIndex = self.index(row, col, index)
childState = self.data(childIndex, QtCore.Qt.CheckStateRole)
# if the state of a children is partially checked we can
# stop here and return a partially checked state
if childState == QtCore.Qt.PartiallyChecked:
return QtCore.Qt.PartiallyChecked
childStates.append(childState)
if all(childStates):
# all children are checked, yay!
return QtCore.Qt.Checked
elif any(childStates):
# only some children are checked...
return QtCore.Qt.PartiallyChecked
# no item is checked, so bad :-(
return QtCore.Qt.Unchecked
return super(TreeModel, self).data(index, role)
def checkStateChange(self, topLeft, bottomRight):
# if you need some control back to your data outside the model, here is
# the right place to do it; note that *usually* the topLeft and
# bottomRight indexes are the same, expecially with QStandardItemModels
# but that would not be the same in some special cases
pass
class Window(QtWidgets.QWidget):
def __init__(self):
QtWidgets.QWidget.__init__(self)
layout = QtWidgets.QGridLayout()
self.setLayout(layout)
self.treeView = QtWidgets.QTreeView()
layout.addWidget(self.treeView)
self.models = []
self.expandStates = {}
for i, dataSet in enumerate(dataSets):
model = TreeModel(dataSet)
button = QtWidgets.QPushButton('Data-{:02}'.format(i + 1))
layout.addWidget(button)
button.clicked.connect(lambda _, model=model: self.setModel(model))
def getExpandState(self, expDict, model, index=QtCore.QModelIndex()):
# set the index expanded state, if it's not the root index:
# the root index is not a valid index!
if index.isValid():
expDict[index] = self.treeView.isExpanded(index)
# if the index (or root index) has children, set their states
for row in range(model.rowCount(index)):
for col in range(model.columnCount(index)):
childIndex = model.index(row, col, index)
# if the current index has children, set their expand state
# using this function, which is recursive
for childRow in range(model.rowCount(childIndex)):
self.getExpandState(expDict, model, childIndex)
def setModel(self, model):
if self.treeView.model():
if self.treeView.model() == model:
# the model is the same, no need to update anything
return
# save the expand states of the current model before changing it
prevModel = self.treeView.model()
self.expandStates[prevModel] = expDict = {}
self.getExpandState(expDict, prevModel)
self.treeView.setModel(model)
if model in self.expandStates:
# if the new model has expand states saved, restore them
for index, expanded in self.expandStates.get(model, {}).items():
self.treeView.setExpanded(index, expanded)
else:
self.treeView.expandAll()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
w = Window()
w.show()
sys.exit(app.exec_())
[1]: In this example the dataChanged signal is emitted whenever any child item check state changes. This isn't a big issue, but if you really need to avoid unnecessary dataChanged notifications you might need to add a QtCore.QTimer.singleshot delayed dataChanged signal emission only if the parent state has changed. It's not that hard to achieve, but I didn't think it was really necessary for this example.