Python: third Friday of a month

Question

I am a rookie python programmer and I need to write a script to check if a given date (passed as a string in the form \'Month, day year\') is the third Friday of the month. I am

Answer 1

This should do it:

from datetime import datetime 

def is_third_friday(s):
    d = datetime.strptime(s, '%b %d, %Y')
    return d.weekday() == 4 and 15 <= d.day <= 21

Test:

print is_third_friday('Jan 18, 2013')  # True
print is_third_friday('Feb 22, 2013')  # False
print is_third_friday('Jun 21, 2013')  # True
print is_third_friday('Sep 20, 2013')  # True

Answer 2

Yet another way to accomplish this... using integer division...

import datetime

def is_date_the_nth_friday_of_month(nth, date=None):
    #nth is an integer representing the nth weekday of the month
    #date is a datetime.datetime object, which you can create by doing datetime.datetime(2016,1,11) for January 11th, 2016

    if not date:
        #if date is None, then use today as the date
        date = datetime.datetime.today()

    if date.weekday() == 4:
        #if the weekday of date is Friday, then see if it is the nth Friday
        if (date.day - 1) // 7 == (nth - 1):
            #We use integer division to determine the nth Friday
            #if this integer division == 0, then date is the first Friday, 
            # if the integer division is...
            #   1 == 2nd Friday
            #   2 == 3rd Friday
            #   3 == 4th Friday
            #   4 == 5th Friday
            return True

    return False

Answer 3

you can use something like this to get third fridday of the month (current month), and then simply compare that third_friday with your day (by year, month, day)

from datetime import datetime, timedelta
import calendar

now = datetime.now()
first_day_of_month = datetime(now.year, now.month, 1)
first_friday = first_day_of_month + timedelta(days=((4-calendar.monthrange(now.year,now.month)[0])+7)%7)
# 4 is friday of week
third_friday = first_friday + timedelta(days=14)

Hope this helps.

Answer 4

If you're trying to find the expiration of an option, you could use something like this

from datetime import datetime
import calendar

def option_expiration(date):
    day = 21 - (calendar.weekday(date.year, date.month, 1) + 2) % 7
    return datetime(date.year, date.month, day)

print option_expiration(datetime.today())

Answer 5

This is the nicest I've found so far.

from datetime import date
from dateutil.relativedelta import relativedelta, FR

def get_third_fri_of_mth(dt):
    print (dt + relativedelta(day=1, weekday=FR(3)))

get_third_fri_of_mth(date(2019, 1, 30))
get_third_fri_of_mth(date(2019, 6, 4))

Relative delta replaces the day in the date you specify by day = 1. From this new date, weekday=FR(3) specifies the 3rd friday.