find_mon25.py

"""A small script to find all months that have a Monday 25th for a particular
year.
Input: year in format YYYY
Output: print list of dates that are a Monday 25 in that year
"""
import re
import sys
from typing import Iterator
from datetime import date

VALID_YEAR_FORMAT = re.compile(r"(\d{4})")
REQUIRED_DAY_NUMBER = 25
MONDAY = 0


def _get_raw_input() -> str:
    if len(sys.argv) > 1:
        return sys.argv[1]
    return input("Enter year (YYYY): ")


def _validate_and_parse_raw_input(raw_input: str) -> int:
    if year := re.match(VALID_YEAR_FORMAT, raw_input):
        return int(year.group(0))
    raise RuntimeError(f"{raw_input!r} doesn't comply with the format (YYYY)")


def parse_input() -> int:
    raw_input = _get_raw_input()
    return _validate_and_parse_raw_input(raw_input)


def _is_monday(a_date: date) -> bool:
    return a_date.weekday() == MONDAY


def find_all_required(year: int) -> Iterator[date]:
    for month in range(1, 12 + 1):
        candidate = date(year, month, REQUIRED_DAY_NUMBER)
        if _is_monday(candidate):
            yield candidate


def display(dates: Iterator[date]):
    for day in dates:
        print(day.strftime("%A %d of %B, %Y"))


def main():
    year: int = parse_input()
    results_found = find_all_required(year)
    display(results_found)


if __name__ == "__main__":
    main()