Populating a ListView with Python Objects

[christofer]

I want to populate a ListView with objects from Python. I've been able to make a ListView work using ListModel+ ListElement in QML but not from Python. From what I've read, it seems I should use a QAbstractListModel but so far I haven't been able to get the values of the python objects to show up. It seems my QAbstractListModel's rowCount() and data() functions don't even get called.

I posted a (hopefully) lean example in a GitLab project

What am I missing?
Thanks,
-chris

[christofer]

@Denni-0 Thanks for the tips Denni!

[JonB]

@christofer
Having glanced at your code. I can't help you if you say rowCount() or data() are never called. I know nothing about QML so only you know if your code is being called. It looks fine as-is except that your data() method needs work.

    def data(self, index, role=Qt.DisplayRole):
        print("data: " + self.items)
        return self.items

First it must return the correct indvidual element according to the index: QModelIndex parameter, and second it must only do so for the DisplayRole case on the role parameter, not for all cases as you have done. Until you have done those 2 it won't work right.

If/when that's sorted out, you're trying to have data() return a class MyItem data item, say for the DisplayRole when it wants to show it. I can't imagine what a Qt view is going to make of that. If you're lucky it might use str(instanceMyItem), and I don't know what that looks like.

[christofer]

@JonB @Denni-0 I've made changes based on your feedback. Thanks. Still not sure the changes are correct because the functions do not get called. But at least it's closer to correct.

[christofer]

@Denni-0 just a side note, but the PySide2 QCoreApplication, QGuiApplication, and QApplication have exec_() functions. The docs say things like "see exec()" but it doesn't exist. I get an AttributeError if I try to use it. I'm using PySide2 version 5.14.1

[eyllanesc]

@christofer You cannot expose a Python Object to QML, what you can do is export a QObject through the model as I have implemented in the PR to your repo.

[eyllanesc]

@christofer You can also make the model expose each attribute of the items through the roles as I show in my second PR

[JonB]

@christofer said in Populating a ListView with Python Objects:

Still not sure the changes are correct because the functions do not get called

That sounds like a QML issue. You should heed what @eyllanesc has written, as he seems to know about Python to QML.

It really does not matter to try to change from exec_() to exec(). PyQt exposes an exec() (as well as exec_()), PySide does not. As I said, nothing in your existing code I saw needed changing, it was not PyQt4 syntax, it was all correct, except for the implementation of data().

[christofer]

Thanks @eyllanesc for the MRs! They're very helpful.

On using roles for a and b (commit 1e5447) vs just using the display role (commit 83b42b) ... which do you recommend? I like the simple access in the QML model.a, model.b but it seems like making custom roles could conflict with Qt expecting the roles in PySide2.QtCore.Qt.ItemDataRole which makes me think model.display.a, model.display.b is a safer long-term solution.

[lbt_]

Old post but Google led me here so it seemed like a place to drop a super-simple solution.

One approach that works very easily if you have a python list of QObject derived objects is to pass a QVariantList of QObjects and access them via @Property

class MyItemModel(QObject):
...
    @Property(str)
    def name(self):
        return self.m_name

class MyDataModel(QObject):
...
    @Property('QVariantList')
    def names(self):
        return list(self.m_item_objects_list) 

QML:

LiistView {
  id: lv
    model: mydatamodelinstance.names // setContextProperty of a MyDataModel object
    delegate: { Text { text: modelData.name } }  // This gets the name property of a MyItemModel
}