tkinter tkcalendar to display events

Question

I am trying to use tkcalendar to display some events in my python tkinter application. I have a database of events and i put them in the calendar as in the following example (I have created a dictionary of events to show the case). In this example I loop over all events and put them all in the calendar

import tkinter as tk
import tkinter.ttk as ttk
from tkinter import *
import tkcalendar
from tkcalendar import Calendar, DateEntry
import datetime

root = tk.Tk()

events={'2018-09-28':('London','meeting'),\
    '2018-08-15':('Paris','meeting'),\
    '2018-07-30':('New York','meeting')}

cal = Calendar(root, selectmode='day', year=2018, month=8)

for k in events.keys():
    date=datetime.datetime.strptime(k,"%Y-%m-%d").date()
    cal.calevent_create(date, events[k][0], events[k][1])

cal.tag_config('meeting', background='red', foreground='yellow')
cal.pack(fill="both", expand=True)

root.mainloop()

Up to now everything fine. The problem is that the database of events is quite large and expands several years. Ideally I would want to create only the events of the month being displayed. I need to detect when the user clicks on "Next month" and "Previous Month" (the standard buttons that come with the tkcalendar):

and create the events for the month being displayed. Is that even possible?

thank you very much in advance

Answer 1

You can create a class inheriting from Calendar and redefine the callbacks of the "Next month" and "Previous Month" buttons so that they generate a virtual event '<<CalendarMonthChanged>>'. Then bind this event to a function that displays the current month events.

Here is the code:

from tkcalendar import Calendar
from tkinter import Tk


class MyCalendar(Calendar):

    def _next_month(self):
        Calendar._next_month(self)
        self.event_generate('<<CalendarMonthChanged>>')

    def _prev_month(self):
        Calendar._prev_month(self)
        self.event_generate('<<CalendarMonthChanged>>')

    def _next_year(self):
        Calendar._next_year(self)
        self.event_generate('<<CalendarMonthChanged>>')

    def _prev_year(self):
        Calendar._prev_year(self)
        self.event_generate('<<CalendarMonthChanged>>')

    def get_displayed_month_year(self):
        return self._date.month, self._date.year


def on_change_month(event):
    # remove previously displayed events
    cal.calevent_remove('all')
    year, month = cal.get_displayed_month_year()
    # display the current month events 
    # ...
    print(year, month)

root = Tk()
cal = MyCalendar(root)
cal.pack()

cal.bind('<<CalendarMonthChanged>>', on_change_month)

root.mainloop()