How to add "Select one..." to QComboBox when using QAbstractTableModel (Model/View)?

Question

I'm using a QAbstractTableModel to populate a QComboBox. This works great, but I wish to always have the very first combobox index to contain a value of "Select one...".

Is this possible, and if so - how?

---

I have a combobox, which I set a model to:

model = ProjectTableModel(projects)
combobox.setModel(model)

My model:

class ProjectTableModel(QtCore.QAbstractTableModel):

    def __init__(self, projects=[], parent=None):
        QtCore.QAbstractTableModel.__init__(self, parent)
        self._projects = projects

    def rowCount(self, parent):
        return len(self._projects)

    def columnCount(self, parent):
        return 2

    def data(self, index, role):
        row = index.row()
        column = index.column()

        if role == QtCore.Qt.DisplayRole and column == 0:
            # Set the item's text
            project = self._projects[row]
            name = project.name()
            return name
        elif role == QtCore.Qt.UserRole and column == 0:
            # Set the "itemData"
            project = self._projects[row]
            id = project.id()
            return id

Answer 1

You can add an appropriate condition when getting/setting values and adjust the row count/number where necessary. The example below shows how to do this, but you should check all your code carefully to make sure the row is always adjusted properly when accessing the _projects items. (And note that you don't need to to adjust the row number when accessing rows in the model itself).

class ProjectTableModel(QtCore.QAbstractTableModel):

    def __init__(self, projects=[], parent=None):
        QtCore.QAbstractTableModel.__init__(self, parent)
        self._projects = projects

    def rowCount(self, parent):
        return len(self._projects) + 1 # adjust row count

    def columnCount(self, parent):
        return 2

    def data(self, index, role):
        row = index.row() - 1 # adjust row number
        column = index.column()

        if role == QtCore.Qt.DisplayRole and column == 0:
            if row >= 0:
                # Set the item's text
                project = self._projects[row]
                return project.name()
            else:
                return 'Select one...'
        elif role == QtCore.Qt.UserRole and column == 0 and row >= 0:
            # Set the "itemData"
            project = self._projects[row]
            id = project.id()
            return id

    def setData(self, index, value, role):
        row = index.row() - 1  # adjust row number
        column = index.column()

        # ignore the first item in the model
        if role == QtCore.Qt.DisplayRole and column == 0 and row >= 0:
            project = self._projects[row]
            project.setName(value) # or whatever