How to create an empty row in GTKTreeView?

Question

How can I create an empty row (2 floats) in GTKTreeView? I set up this:

    self.liststore = Gtk.ListStore(float, float)
    self.treeview = Gtk.TreeView(model=self.liststore)

and then add 3 rows:

    self.liststore.append([2.35, 2.40])
    self.liststore.append([3.45, 4.70])
    self.liststore.append()

but the 3rd row is filled with 0.00000 each when I execute the program. How can I create a true empty row? Or how can I display an empty row in GtkTreeView?

I am working on a program that plots points and adds a new row each time the empty row is filled:

    #!/usr/bin/python3

    from gi.repository import Gtk
    from matplotlib.figure import Figure
    from matplotlib.backends.backend_gtk3agg import FigureCanvasGTK3Agg as FigureCanvas

    class DataBase():
        def __init__(self):
            self.window = Gtk.Window()
            self.window.set_default_size(800, 500)
            self.box = Gtk.Box()
            self.window.add(self.box)

            self.fig = Figure(figsize=(10,10), dpi=80)
            self.ax = self.fig.add_subplot(111)

            self.canvas = FigureCanvas(self.fig)
            self.box.pack_start(self.canvas, True, True, 0)

            self.liststore = Gtk.ListStore(float, float)
            self.treeview = Gtk.TreeView(model=self.liststore)
            self.box.pack_start(self.treeview, False, True, 0)

            self.xrenderer = Gtk.CellRendererText()
            self.xrenderer.set_property("editable", True)
            self.column_text = Gtk.TreeViewColumn("x-Value", self.xrenderer, text=0)
            self.treeview.append_column(self.column_text)

            self.yrenderer = Gtk.CellRendererText()
            self.yrenderer.set_property("editable", True)
            self.column_editabletext = Gtk.TreeViewColumn("y-Value", self.yrenderer, text=1)
            self.treeview.append_column(self.column_editabletext)

            self.xrenderer.connect("edited", self.xedited)
            self.yrenderer.connect("edited", self.yedited)

            self.liststore.append([2.35, 2.40])
            self.liststore.append([3.45, 4.70])
            self.liststore.append()

        def resetplot(self):
            self.ax.cla()
            self.ax.set_xlim(0,10)
            self.ax.set_ylim(0,10)
            self.ax.grid(True)

        def plotpoints(self):
            self.resetplot()
            for row in self.liststore:
                self.ax.scatter(row[:1], row[1:], marker='o', s=50)
            self.fig.canvas.draw()

        def xedited(self, widget, path, number):
            self.liststore[path][0] = float(number.replace(',', '.'))
            self.plotpoints()

        def yedited(self, widget, path, number):
            self.liststore[path][1] = float(number.replace(',', '.'))
            self.plotpoints()

    db = DataBase()
    db.resetplot()
    db.plotpoints()

    db.window.connect("delete-event", Gtk.main_quit)
    db.window.show_all()
    Gtk.main()

Answer 1

I don't think you can, just don't add a row unless you've got data for it, unless you store strings in the model. Then you can have empty strings for the empty rows.