Simple date counter

calendar.glade

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.38.2 -->
<interface>
  <requires lib="gtk+" version="3.24"/>
  <object class="GtkAdjustment" id="adjustment1">
    <property name="upper">100</property>
    <property name="step-increment">1</property>
    <property name="page-increment">10</property>
  </object>
  <object class="GtkAdjustment" id="adjustment2">
    <property name="upper">100</property>
    <property name="step-increment">1</property>
    <property name="page-increment">10</property>
  </object>
  <object class="GtkAction" id="resetAction">
    <property name="label" translatable="yes">Reset</property>
    <property name="stock-id">gtk-cancel</property>
  </object>
  <object class="GtkTextBuffer" id="textbuffer1"/>
  <object class="GtkWindow" id="window1">
    <property name="can-focus">False</property>
    <child>
      <!-- n-columns=3 n-rows=3 -->
      <object class="GtkGrid">
        <property name="visible">True</property>
        <property name="can-focus">False</property>
        <child>
          <object class="GtkCalendar" id="calendar1">
            <property name="visible">True</property>
            <property name="can-focus">True</property>
            <property name="year">2021</property>
            <property name="month">11</property>
            <property name="day">7</property>
          </object>
          <packing>
            <property name="left-attach">0</property>
            <property name="top-attach">1</property>
          </packing>
        </child>
        <child>
          <object class="GtkBox">
            <property name="visible">True</property>
            <property name="can-focus">False</property>
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkBox">
                <property name="visible">True</property>
                <property name="can-focus">False</property>
                <child>
                  <object class="GtkLabel">
                    <property name="visible">True</property>
                    <property name="can-focus">False</property>
                    <property name="label" translatable="yes">Total dates selected: </property>
                  </object>
                  <packing>
                    <property name="expand">False</property>
                    <property name="fill">True</property>
                    <property name="position">0</property>
                  </packing>
                </child>
                <child>
                  <object class="GtkLabel" id="countLabel">
                    <property name="visible">True</property>
                    <property name="can-focus">False</property>
                    <property name="label" translatable="yes">0</property>
                    <property name="justify">right</property>
                  </object>
                  <packing>
                    <property name="expand">False</property>
                    <property name="fill">True</property>
                    <property name="position">1</property>
                  </packing>
                </child>
                <child>
                  <placeholder/>
                </child>
              </object>
              <packing>
                <property name="expand">False</property>
                <property name="fill">True</property>
                <property name="position">0</property>
              </packing>
            </child>
            <child>
              <object class="GtkScrolledWindow">
                <property name="visible">True</property>
                <property name="can-focus">True</property>
                <property name="shadow-type">in</property>
                <child>
                  <object class="GtkTextView" id="text">
                    <property name="visible">True</property>
                    <property name="can-focus">True</property>
                    <property name="hexpand">True</property>
                    <property name="vexpand">True</property>
                    <property name="hadjustment">adjustment1</property>
                    <property name="vadjustment">adjustment2</property>
                    <property name="editable">False</property>
                    <property name="justification">right</property>
                    <property name="buffer">textbuffer1</property>
                  </object>
                </child>
              </object>
              <packing>
                <property name="expand">False</property>
                <property name="fill">True</property>
                <property name="position">1</property>
              </packing>
            </child>
            <child>
              <placeholder/>
            </child>
          </object>
          <packing>
            <property name="left-attach">1</property>
            <property name="top-attach">1</property>
          </packing>
        </child>
        <child>
          <object class="GtkMenuBar">
            <property name="visible">True</property>
            <property name="can-focus">False</property>
            <child>
              <object class="GtkMenuItem">
                <property name="visible">True</property>
                <property name="can-focus">False</property>
                <property name="label" translatable="yes">_File</property>
                <property name="use-underline">True</property>
                <child type="submenu">
                  <object class="GtkMenu">
                    <property name="visible">True</property>
                    <property name="can-focus">False</property>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-new</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-open</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-save</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-save-as</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkSeparatorMenuItem">
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-quit</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkMenuItem">
                <property name="visible">True</property>
                <property name="can-focus">False</property>
                <property name="label" translatable="yes">_Edit</property>
                <property name="use-underline">True</property>
                <child type="submenu">
                  <object class="GtkMenu">
                    <property name="visible">True</property>
                    <property name="can-focus">False</property>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-cut</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-copy</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-paste</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-delete</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                    <child>
                      <object class="GtkImageMenuItem" id="resetMenuItem">
                        <property name="label">gtk-cancel</property>
                        <property name="related-action">resetAction</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="tooltip-text" translatable="yes">Reset</property>
                        <property name="action-name">resetAction</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkMenuItem">
                <property name="visible">True</property>
                <property name="can-focus">False</property>
                <property name="label" translatable="yes">_View</property>
                <property name="use-underline">True</property>
              </object>
            </child>
            <child>
              <object class="GtkMenuItem">
                <property name="visible">True</property>
                <property name="can-focus">False</property>
                <property name="label" translatable="yes">_Help</property>
                <property name="use-underline">True</property>
                <child type="submenu">
                  <object class="GtkMenu">
                    <property name="visible">True</property>
                    <property name="can-focus">False</property>
                    <child>
                      <object class="GtkImageMenuItem">
                        <property name="label">gtk-about</property>
                        <property name="visible">True</property>
                        <property name="can-focus">False</property>
                        <property name="use-underline">True</property>
                        <property name="use-stock">True</property>
                      </object>
                    </child>
                  </object>
                </child>
              </object>
            </child>
          </object>
          <packing>
            <property name="left-attach">0</property>
            <property name="top-attach">0</property>
          </packing>
        </child>
        <child>
          <placeholder/>
        </child>
        <child>
          <placeholder/>
        </child>
        <child>
          <placeholder/>
        </child>
        <child>
          <placeholder/>
        </child>
        <child>
          <placeholder/>
        </child>
        <child>
          <placeholder/>
        </child>
      </object>
    </child>
  </object>
</interface>

main.py

#!/usr/bin/env python
import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, GLib, GObject, Gio


class application_gui:
    """Tutorial 08 menu, calendar widget."""
    count = 0

    def __init__(self):
        #load in our glade interface
        super().__init__()
        xml = Gtk.Builder()
        xml.add_from_file('calendar.glade')

        #grab our widget using get_object this is the name of the widget from glade, window1 is the default name
        self.window = xml.get_object('window1')
        self.text = xml.get_object('text').get_buffer()
        self.dates = set()

        #load our widgets from the glade file
        self.widgets = {}
        self.widgets['calendar'] = xml.get_object('calendar1')
        self.widgets['countLabel'] = xml.get_object('countLabel')
        self.widgets['calendar'].select_month(9,2021)
        #self.widgets['menushow'] = xml.get_object('menuitem6')
        #self.widgets['menuhide'] = xml.get_object('menuitem7')
        #self.widgets['menuhello'] = xml.get_object('menuitem8')

        #connect to events, in this instance just quit our application
        self.window.connect('delete_event', Gtk.main_quit)
        self.window.connect('destroy', lambda quit: Gtk.main_quit())
        xml.get_object('resetAction').connect('activate', self._reset)
        #self.widgets['menushow'].connect('activate', self.showcalendar)
        #self.widgets['menuhide'].connect('activate', self.hidecalendar)
        #self.widgets['menuhello'].connect('activate', self.hello)
        self.widgets['calendar'].connect('day-selected-double-click', self.date_selected)

        #show the window else there is nothing to see :)
        self.window.show()

    def _reset(self):
        self.text.set_text('')
        self.widgets['countLabel'].set_text('0')
        self.widgets['calendar'].select_month(7,2021)

    def hidecalendar(self, *args):
        self.widgets['calendar'].hide()

    def showcalendar(self, *args):
        self.widgets['calendar'].show()

    def hello(self, *args):
        self.text.set_text('hello world')

    def _date_str_to_str(self, date):
        return str(date[2]) + '-'+str(date[1]+1) + '-' + str(date[0])
        
    def dates_to_str(self):
        return '\n'.join(map(self._date_str_to_str, sorted(self.dates, reverse=True)))
        
    def date_selected(self, *args):
        date = self.widgets['calendar'].get_date()
        self.dates.add(date)
        start,end = self.text.get_bounds()
        #old_text = self.text.get_text(start,end, False)
        #new_text = old_text + '\n' + str(date[2]) + '-'+str(date[1]) + '-' + str(date[0])
        new_text = self.dates_to_str()
        self.text.set_text(new_text)
        self.widgets['countLabel'].set_text(str(len(self.dates)))
        
application = application_gui()
Gtk.main()