Determine the nth week of the month for a given date string.

det_nth_wk_of_month.py

#!/usr/bin/env python3
import calendar
from datetime import date

import numpy as np


def ordinal(n):
    """Converts an integer to its ordinal representation.
    Reference:
        https://stackoverflow.com/a/16671271/11042987
    """
    return str(n) + (
        "th" if 4 <= n % 100 <= 20
        else {1: "st", 2: "nd", 3: "rd"}.get(n % 10, "th"))


class DateAttrs:
    def __init__(self, date_string):
        self.my_date = date.fromisoformat(date_string) if date_string else date.today()
        self.yr = self.my_date.year
        self.mo = self.my_date.month
        self.dy = self.my_date.day
        self.dow = self.my_date.strftime('%a')
        self.wk_num = self.my_date.isocalendar().week
        self.wk_day = self.my_date.isocalendar().weekday

    def determine_nth_wk_of_month(self):
        # Calendar array
        arr = np.array(calendar.monthcalendar(self.yr, self.mo))
        # Find the row number and convert it to nth week of the month.
        return np.argwhere(arr == self.dy)[0, 0] + 1  # Add 1 for 1-based indexing.

    def display_calendar_with_comments(self):
        print(f'''\033[93m{self.dow}, {self.my_date.isoformat()} is
  the {ordinal(self.determine_nth_wk_of_month())} week of the month.
  the {ordinal(self.wk_num)} week of the year\033[0m
See the calendar below:\n''')
        print(calendar.month(self.yr, self.mo))


def set_week_start(start_day):
    """Sets the starting day of the week for the calendar module.
    Args:
        start_day (str): A string representing the desired starting day.
    """
    # noinspection PyCompatibility
    match start_day.lower():
        case 'sat':
            calendar.setfirstweekday(calendar.SATURDAY)
        case 'sun':
            calendar.setfirstweekday(calendar.SUNDAY)
        case _:
            calendar.setfirstweekday(calendar.MONDAY)


if __name__ == '__main__':
    set_week_start(input('First day of the week? (Mon, Sat, Sun; default: Mon) >> '))
    my_instance = DateAttrs(input('Date? [yyyy-mm-dd] >> '))
    my_instance.display_calendar_with_comments()