[kwlug-disc] Question Involving GTK 3 Programming in Python

[John Driezen]

Thank you Paul.  Your suggestion of making material_combo an instance 
variable by prepending self. works, and makes my code much cleaner.

John Driezen

jdriezen at sympatico.ca

On 2021-05-01 2:49 p.m., Paul Nijjar via kwlug-disc wrote
> You prepend 'self.' in front of instance variables:
>
> class ScrapAppWindow(Gtk.Window):
>
>      # ... snip ...
>
>      def __init__(self):
>          Gtk.Window.__init__(self, title="Scrap App")
>          self.set_border_width(10)
>
>          material_label = Gtk.Label(label="Please Select Material")
>
>          material_store = Gtk.ListStore(str)
>
>          material_store.append(["#1 Bright Copper"])
>          material_store.append(["#1 Copper"])
>
>          # ... snip ...
>
>          # This will make self.material_combo available in the class, I think
>          self.material_combo = Gtk.ComboBox.new_with_model(material_store)
>          self.material_combo.connect("changed", self.on_material_combo_changed)
>          renderer_text = Gtk.CellRendererText()
>          self.material_combo.pack_start(renderer_text, True)
>          self.material_combo.add_attribute(renderer_text, "text", 0)
>
>          plot_button = Gtk.Button.new_with_label("Plot Graph")
>          plot_button.connect("clicked", self.on_plot_graph_clicked)
>
>          vbox = Gtk.Box(orientation = Gtk.Orientation.VERTICAL, spacing=10)
>          vbox.pack_start(material_label, True, True, 0)
>          vbox.pack_start(self.material_combo, True, True, 0)
>          vbox.pack_start(plot_button, True, True, 0)
>
>          self.add(vbox)
>          self.show_all()
>
> Then your on_plot_graph_clicked() function becomes something like:
>
> def on_plot_graph_clicked(self, button):
>      print('"Plot Graph" Button was clicked.')
>
>      selected_material = None
>
>      tree_iter = self.material_combo.get_active_iter()
>      if tree_iter is not None:
>         model = self.material_combo.get_model()
>         selected_material = model[tree_iter][0]
>
>      if (selected_material is None) or (selected_material=="All Materials"):
>          dialog = Gtk.MessageDialog(
>                       transient_for=self,
>                       flags=0,
>                       message_type=Gtk.MessageType.INFO,
>                       buttons=Gtk.ButtonsType.OK,
>                       text="Please select a material.",
>                   )
>          dialog.run()
>          print("Plot Graph dialog closed.")
>          dialog.destroy()
>      else:
>          print("Calling plotgraph(%s)."� % selected_material)
>          plotgraph(selected_material)
>
>
> (I did not test this, and I could be very very wrong, but I believe this is how you set up classes in Python. See: https://www.digitalocean.com/community/tutorials/understanding-class-and-instance-variables-in-python-3
>
> - Paul
>
>> On 2021-04-29 3:41 p.m., Paul Nijjar via kwlug-disc wrote:
>>> You have a class ScrapAppWindow. My (possibly wrong) idea would be to
>>> make material_combo a class variable, rather than a variable that is
>>> local to the init() function. Then it will be accessible from your
>>> other functions.
>>>
>>> - Paul
>>>
>>>
>> Your suggestion is a good one Paul.  However I am at a total loss on how to
>> implement your suggestion in Python.
>>
>> I did manage to get the Plot Graph button working by passing the
>> material_combo variable to the on_plot_graph_clicked method. Sample code
>> follows:
>>
>> def on_plot_graph_clicked(self, button, combo):
>>      print('"Plot Graph" Button was clicked.')
>>
>>      selected_material = None
>>
>>      tree_iter = combo.get_active_iter()
>>      if tree_iter is not None:
>>      model = combo.get_model()
>>      selected_material = model[tree_iter][0]
>>
>>      if (selected_material is None) or (selected_material=="All Materials"):
>>          dialog = Gtk.MessageDialog(
>>                       transient_for=self,
>>                       flags=0,
>>                       message_type=Gtk.MessageType.INFO,
>>                       buttons=Gtk.ButtonsType.OK,
>>                       text="Please select a material.",
>>                   )
>>          dialog.run()
>>          print("Plot Graph dialog closed.")
>>          dialog.destroy()
>>      else:
>>          print("Calling plotgraph(%s)." % selected_material)
>>          plotgraph(selected_material)
>>
>> I am calling the on_plot_graph_clicked method using this line.
>>
>> plot_button.connect("clicked", self.on_plot_graph_clicked, material_combo)
>>
>> My solution works, but becomes unwieldy very quickly with multiple combo
>> boxes.
>>
>> John Driezen
>> jdriezen at sympatico.ca
>>
>> On 2021-04-29 3:41 p.m., Paul Nijjar via kwlug-disc wrote:
>>> You have a class ScrapAppWindow. My (possibly wrong) idea would be to
>>> make material_combo a class variable, rather than a variable that is
>>> local to the init() function. Then it will be accessible from your
>>> other functions.
>>>
>>> - Paul
>>>
>>>
>> _______________________________________________
>> kwlug-disc mailing list
>> kwlug-disc at kwlug.org
>> https://kwlug.org/mailman/listinfo/kwlug-disc_kwlug.org