Simple library for parsing some human readable dates. Setup as a jinja2 filter

dateparser.py

import re
import calendar
from datetime import datetime

from dateutil.relativedelta import relativedelta


_day_of_week_to_ = {
    "day": 0,
    "monday": 0,
    "tuesday": 1,
    "wednesday": 2,
    "thursday": 3,
    "friday": 4,
    "saturday": 5,
    "sunday": 6
}

_advance_to_ = {
    "this": +0,
    "the": +0,
    "next": +1,
    "last": -1
}

_time_period_to_ = {
    "month": "months",
    "week": "weeks"
}


class FilterModule:

    def filters(self):
        return {'parse_human_date': self.parse_date}

    @staticmethod
    def parse_date(human_date):
        try:
            num_value = int(re.match(r"(\d+)", human_date).group())
        except (AttributeError, ValueError):
            raise ValueError("It seems that you may not have specified a number of something. e.g. '5th' day")

        try:
            weekday = re.search(
                r"(\bday\b|\bMo(nday)?\b|\bTu(e(sday)?)?\b|\bWe(d(nesday)?)?\b|\bTh(ur(sday)?)?\b|\bFr(i(day)?)?\b|\bSa(t(urday)?)?\b|\bSu(n(day)?)?\b)",
                human_date
            ).group().lower()
        except AttributeError:
            raise ValueError("It seems that you may not have specified a day. e.g. 'day' or 'Friday'")

        try:
            advance = re.search(r"(\bnext\b|\blast\b|\bthis\b|\bthe\b)", human_date).group()
        except AttributeError as e:
            raise ValueError("It seems that you may not have specified a advance direction. e.g. 'next' or 'last' or 'this'")

        try:
            time_period = re.search(r"(\bmo(nth)?\b)", human_date).group()
        except AttributeError:
            raise ValueError("It seems that you may not have specified a time period. e.g. 'month' or 'week'")

        today = datetime.now().replace(hour=0, minute=0, second=0, microsecond=0)

        options = {
            _time_period_to_[time_period]: _advance_to_[advance]
        }

        new_date = today + relativedelta(**options)
        month_cal = calendar.monthcalendar(new_date.year, new_date.month)

        if weekday == "day" and time_period == "month":
            new_date = new_date.replace(day=num_value)
        # issues getting to previous week or next week
        # elif time_period == "week":
        #     for week in month_cal:
        #         if new_date.day in week:
        #             the_week = week
        #             break
        #     new_date = new_date.replace(
        #         day=the_week[num_value - 2]
        #     )
        else:
            first_week = month_cal[0]
            the_day = first_week[_day_of_week_to_[weekday]]

            new_date = new_date.replace(
                day=month_cal[
                    num_value if the_day == 0 else num_value - 1
                ][
                    _day_of_week_to_[weekday]
                ]
            )

        return new_date


if __name__ == "__main__":
    print(FilterModule.parse_date("1st day of next month"))
    print(FilterModule.parse_date("2nd Friday of this month"))
    print(FilterModule.parse_date("1st Sunday of next month"))
    print(FilterModule.parse_date("5th day of next month"))
    print(FilterModule.parse_date("2nd Tuesday of this month"))

    # print(FilterModule.parse_date("1rd day of last week"))
    # print(FilterModule.parse_date("1st day of next week"))

Main issue with this I'm having troubles with is getting "someday of last week". But I dont need it for what I'm using this library for so feel free to add to it.