Add n business days to a given date ignoring holidays and weekends in python

Question

I\'m trying to add n (integer) working days to a given date, the date addition has to avoid the holidays and weekends (it\'s not included in the working days)

Answer 1

If someone needs to add/substract days, extending @omz's answer:

def add_business_days(from_date, ndays):
    business_days_to_add = abs(ndays)
    current_date = from_date
    sign = ndays/abs(ndays)
    while business_days_to_add > 0:
        current_date += datetime.timedelta(sign * 1)
        weekday = current_date.weekday()
        if weekday >= 5: # sunday = 6
            continue
        business_days_to_add -= 1
    return current_date

Answer 2

similar to @omz solution but recursively:

def add_days_skipping_weekends(start_date, days):
    if not days:
        return start_date
    start_date += timedelta(days=1)
    if start_date.weekday() < 5:
        days -= 1
    return add_days_skipping_weekends(start_date, days)

Answer 3

I wanted a solution that wasn't O(N) and it looked like a fun bit of code golf. Here's what I banged out in case anyone's interested. Works for positive and negative numbers. Let me know if I missed anything.

def add_business_days(d, business_days_to_add):
    num_whole_weeks  = business_days_to_add / 5
    extra_days       = num_whole_weeks * 2

    first_weekday    = d.weekday()
    remainder_days   = business_days_to_add % 5

    natural_day      = first_weekday + remainder_days
    if natural_day > 4:
        if first_weekday == 5:
            extra_days += 1
        elif first_weekday != 6:
            extra_days += 2

    return d + timedelta(business_days_to_add + extra_days)

Answer 4

Hope this helps. It's not O(N) but O(holidays). Also, holidays only works when the offset is positive.

def add_working_days(start, working_days, holidays=()):
    """
    Add working_days to start start date , skipping weekends and holidays.

    :param start: the date to start from
    :type start: datetime.datetime|datetime.date
    :param working_days: offset in working days you want to add (can be negative)
    :type working_days: int
    :param holidays: iterator of datetime.datetime of datetime.date instances
    :type holidays: iter(datetime.date|datetime.datetime)
    :return: the new date wroking_days date from now
    :rtype: datetime.datetime
    :raise:
        ValueError if working_days < 0  and holidays 
    """
    assert isinstance(start, (datetime.date, datetime.datetime)), 'start should be a datetime instance'
    assert isinstance(working_days, int)
    if working_days < 0 and holidays:
        raise ValueError('Holidays and a negative offset is not implemented. ')
    if working_days  == 0:
        return start
    # first just add the days
    new_date = start + datetime.timedelta(working_days)
    # now compensate for the weekends.
    # the days is 2 times plus the amount of weeks are included in the offset added to the day of the week
    # from the start. This compensates for adding 1 to a friday because 4+1 // 5 = 1
    new_date += datetime.timedelta(2 * ((working_days + start.weekday()) // 5))
    # now compensate for the holidays
    # process only the relevant dates so order the list and abort the handling when the holiday is no longer
    # relevant. Check each holiday not being in a weekend, otherwise we don't mind because we skip them anyway
    # next, if a holiday is found, just add 1 to the date, using the add_working_days function to compensate for
    # weekends. Don't pass the holiday to avoid recursion more then 1 call deep.
    for hday in sorted(holidays):
        if hday < start:
            # ignore holidays before start, we don't care
            continue
        if hday.weekday() > 4:
            # skip holidays in weekends
            continue
        if hday <= new_date:
            # only work with holidays up to and including the current new_date.
            # increment using recursion to compensate for weekends
            new_date = add_working_days(new_date, 1)
        else:
            break
    return new_date

Answer 5

Thanks based on omz code i made some little changes ...it maybe helpful for other users:

import datetime
def date_by_adding_business_days(from_date, add_days,holidays):
    business_days_to_add = add_days
    current_date = from_date
    while business_days_to_add > 0:
        current_date += datetime.timedelta(days=1)
        weekday = current_date.weekday()
        if weekday >= 5: # sunday = 6
            continue
        if current_date in holidays:
            continue
        business_days_to_add -= 1
    return current_date

#demo:
Holidays =[datetime.datetime(2012,10,3),datetime.datetime(2012,10,4)]
print date_by_adding_business_days(datetime.datetime(2012,10,2), 10,Holidays)