Generates HTML string of the calendar of given month and year.

calendar_generator.py

import math


def is_leap(year: int) -> bool:
    return year % 4 == 0 and year % 100 != 0 or year % 400 == 0


def residue_year(year: int) -> int:
    return 2 if is_leap(year) else 1


def generate_calendar_html(month: int, year: int) -> str:
    month_names = [
        "January",
        "February",
        "March",
        "April",
        "May",
        "June",
        "July",
        "August",
        "September",
        "October",
        "November",
        "December",
    ]
    month_days = [
        31,
        29 if is_leap(year) else 28,
        31,
        30,
        31,
        30,
        31,
        31,
        30,
        31,
        30,
        31,
    ]

    try:
        days_in_month = month_days[month - 1]
    except IndexError:
        return "<h1>Month numbers must be between 1 and 12.</h1>"

    month_name = month_names[month - 1]
    total_residue = sum([residue_year(i) for i in range(1, year)]) + sum([month_days[i] for i in range(month - 1)])
    day_of_week = total_residue % 7 + 1
    num_rows = math.ceil((days_in_month + day_of_week - 1) / 7)

    html = (
        """
    <h1>%s</h1>
    <table>
        <tr>
            <th>Mo</th>
            <th>Tu</th>
            <th>We</th>
            <th>Th</th>
            <th>Fr</th>
            <th>Sa</th>
            <th>Su</th>
        </tr>
    """
        % month_name
    )

    for row in range(1, num_rows + 1):
        html += "<tr>"

        if row == 1:
            for cell in range(1, day_of_week):
                html += "<td></td>"

            for cell in range(day_of_week, 8):
                curr_day_num = cell + 1 - day_of_week
                html += "<td>%d</td>" % curr_day_num
        else:
            for cell in range(1, 8):
                curr_day_num = (row - 1) * 7 + cell + 1 - day_of_week
                if curr_day_num <= days_in_month:
                    html += "<td>%d</td>" % curr_day_num
                else:
                    html += "<td></td>"

        html += "</tr>"
    html += "</table>"

    return html