belgian_holiday_calendar.py

from pandas.tseries.offsets import Day
from pandas.tseries.holiday import AbstractHolidayCalendar, Holiday, Easter, EasterMonday, weekend_to_monday, nearest_workday

class BelgianHolidayCalendar(AbstractHolidayCalendar):
    rules = [
        Holiday('Nieuwjaar', month=1, day=1, observance=weekend_to_monday),
        EasterMonday,
        Holiday('Dag van de Arbeid', month=5, day=1, observance=nearest_workday),
        Holiday('O.H. Hemelvaart', month=1, day=1, offset=[Easter(), Day(39)]),
        Holiday('Pinkstermaandag', month=1, day=1, offset=[Easter(), Day(50)]),
        Holiday('Nationale feestdag', month=7, day=21, observance=nearest_workday),
        Holiday('O.L.V. hemelvaart', month=8, day=15, observance=nearest_workday),
        Holiday('Allerheiligen', month=11, day=1, observance=nearest_workday),
        Holiday('Wapenstilstand', month=11, day=11, observance=nearest_workday),
        Holiday('Kerstmis', month=12, day=25, observance=nearest_workday)
    ]

number_of_business_days.py

import numpy as np
import pandas as pd
from pandas.tseries.offsets import CustomBusinessDay
from belgian_holiday_calendar import BelgianHolidayCalendar

business_days = pd.date_range('20170101', '20171231', freq=CustomBusinessDay(calendar=BelgianHolidayCalendar()))
business_days_series = pd.Series(np.ones(len(business_days)), index=business_days)

business_days_series.count()

business_days_per_month = business_days_series.resample('M').count()