Question

I am trying to add seconds to python datetime excluding weekends using pandas. The code below works, but I would like to know if there is a simpler way to achieve this.

import datetime
from pandas import *
from pandas.tseries.offsets import *

def add_seconds(start_date, offset_in_seconds):
# get input date in datetime
d = datetime.strptime(start_date, '%Y-%m-%d %H:%M:%S')

# get days, hours, mins, secs
    no_of_days, remainder = divmod(offset_in_seconds, 86400)
    hours, minutes = divmod(remainder, 3600)
    minutes, seconds = divmod(minutes, 60)

# increment the input date  to the appropriate business day
    end_date_pre = d + no_of_days*BDay() 

# dial back to previous evening if hour is under 24
    if 16 + hours < 24:
    end_date = end_date_pre 
    new_end_date = datetime(end_date.year, end_date.month, end_date.day, 16, 0, 0)
    return start_date, end_date, new_end_date.strftime('%Y-%m-%d %H:%M:%S')
# dial forward to the next business day if hour exceeds 24
    elif 16 + hours >= 24:
    end_date = end_date_pre + 1*BDay()
    new_end_date = datetime(end_date.year, end_date.month, end_date.day,9, 0, 0)
    return start_date, end_date, new_end_date.strftime('%Y-%m-%d %H:%M:%S')
    else:
    return start_date, end_date, end_date.strftime('%Y-%m-%d %H:%M:%S')

Answer 1

The dateutil package should be helpful, e.g.

from dateutil.rrule import *    

def add_weekday_seconds(start, x):
    rr = rrule(SECONDLY, byweekday=(MO, TU, WE, TH, FR), dtstart=start, interval=x)
    return rr.after(start)

This (1) uses the rrule class to creates a “repeating date rule” that includes all seconds within Monday through Friday starting on start (which is a datetime), skipping every x seconds; and then (2) executes this rule using the after method which returns the first datetime matching the the rule after the start time — which should be your answer!

Tests of adding 5, 10, and 15 seconds to a start time of 10 seconds before midnight on Friday night, resulting in, respectively, 5 seconds before midnight on Friday, midnight Monday morning, and 5 seconds after midnight Monday morning:

In [131]: friday_night = datetime.datetime(2012, 8, 10, 23, 59, 50)

In [132]: add_weekday_seconds(friday_night, 5)
Out[132]: datetime.datetime(2012, 8, 10, 23, 59, 55)

In [133]: add_weekday_seconds(friday_night, 10)
Out[133]: datetime.datetime(2012, 8, 13, 0, 0)

In [134]: add_weekday_seconds(friday_night, 15)
Out[134]: datetime.datetime(2012, 8, 13, 0, 0, 5)