test_third_friday_month.py

#!/usr/bin/env python
"""Test functions from

http://stackoverflow.com/questions/28680896/how-can-i-get-the-3rd-friday-of-a-month-in-python
"""
import calendar
from datetime import date, datetime, time, timedelta
from itertools import islice

DAY = timedelta(1)
WEEK = 7*DAY

try:
    from dateutil.relativedelta import relativedelta, FR # $ pip install python-dateutil

    def third_friday_dateutil(now, delta=relativedelta(weeks=2, weekday=FR)):
        """the 3rd Friday of the month, not the 3rd Friday after today."""
        now = now.replace(day=1) # 1st day of the month
        return now + delta

    from dateutil.rrule import rrule, MONTHLY, FR

    def third_friday_rrule(now):
        r = rrule(MONTHLY, count=1, byweekday=FR, bysetpos=3, dtstart=now.replace(day=1))
        return r[0].date()

    def get_third_fris_rrule(how_many, now=date.today()):
        r = rrule(MONTHLY, count=how_many, byweekday=FR, bysetpos=3, dtstart=now+DAY)
        return [dt.date() for dt in r]
except ImportError:
    pass

def fridays(now):
    """Generate Fridays starting (including) from now."""
    while True:
        if now.weekday() == calendar.FRIDAY:
            while True:
                yield now
                now += WEEK
        now += DAY

def next_month(now):
    """Return the first date that is in the next month."""
    return (now.replace(day=15) + 20*DAY).replace(day=1)

def third_friday_brute_force(now):
    """the 3rd Friday of the month, not the 3rd Friday after today."""
    return next(islice(fridays(now.replace(day=1)), 2, 3))

def get_third_fris(how_many, now=date.today()):
    result = []
    while len(result) < how_many:
        fr = third_friday_brute_force(now)
        if fr > now: # use only the 3rd Friday after today
            result.append(fr)
        now = next_month(now)
    return result

def third_friday_adam_smith(now, c=calendar.Calendar(firstweekday=calendar.SUNDAY)):
    year, month = now.year, now.month
    monthcal = c.monthdatescalendar(year, month)
    third_friday = [day for week in monthcal for day in week if
                    day.weekday() == calendar.FRIDAY and day.month == month][2]
    return third_friday

def third_friday_juniorcompressor(d):
    s = date(d.year, d.month, 15)
    return s + timedelta(days=(calendar.FRIDAY - s.weekday()) % 7)

def juniorcompressor_next_third_friday(d):
    """ Given a third friday find next third friday"""
    d += timedelta(weeks=4)
    return d if d.day >= 15 else d + timedelta(weeks=1)

def get_third_fris_juniorcompressor(n, d=date.today()):
    """Given a date, calculates n next third fridays"""

    # Find closest friday to 15th of month
    s = date(d.year, d.month, 15)
    result = [s + timedelta(days=(calendar.FRIDAY - s.weekday()) % 7)]

    # This month's third friday passed. Find next.
    if result[0] <= d:
        result[0] = juniorcompressor_next_third_friday(result[0])

    for i in range(n - 1):
        result.append(juniorcompressor_next_third_friday(result[-1]))

    return result

def test(functions, start=date.today(), end=None):
    if end is None:
        end = start.replace(year=start.year + 400) + DAY
    d = start
    while d < end:
        expected = functions[0](d)
        assert all(expected == f(d) for f in functions), (d, [(getattr(f, '__name__', f), f(d)) for f in functions])
        d += DAY

if __name__=="__main__":
    from pprint import pprint
    n = 6
    pprint(get_third_fris_rrule(n))

    from reporttime import get_functions_with_prefix, measure # https://gist.github.com/zed/5650097
    functions = get_functions_with_prefix('third_friday_')
    test(functions)
    measure(functions, [date.today()])

    functions = get_functions_with_prefix('get_third_fris')
    assert get_third_fris_juniorcompressor(n) == get_third_fris(n)
    measure(functions, [n])

    from functools import partial
    test([partial(f, 1) for f in functions])

    n = 12*401
    assert get_third_fris_juniorcompressor(n) == get_third_fris(n)

"""### Output
[datetime.date(2015, 3, 20),
 datetime.date(2015, 4, 17),
 datetime.date(2015, 5, 15),
 datetime.date(2015, 6, 19),
 datetime.date(2015, 7, 17),
 datetime.date(2015, 8, 21)]
name                               time ratio comment
third_friday_juniorcompressor 1.69 usec  1.00 [datetime.date(2015, 2, 27)]
third_friday_brute_force      3.38 usec  2.00 [datetime.date(2015, 2, 27)]
third_friday_dateutil         11.2 usec  6.61 [datetime.date(2015, 2, 27)]
third_friday_adam_smith       18.8 usec 11.12 [datetime.date(2015, 2, 27)]
third_friday_rrule            52.7 usec 31.12 [datetime.date(2015, 2, 27)]
name                                 time ratio comment
get_third_fris_juniorcompressor 15.6 usec  1.00 [6]
get_third_fris                  38.1 usec  2.44 [6]
get_third_fris_rrule             153 usec  9.77 [6]
"""