If I want to find the number of hours between two datetime objects, I can do something like this:
from datetime import datetime
today = datetime.today()
day_after_tomorrow = datetime(2022, 9, 24)
diff = (day_after_tomorrow - today).total_seconds() / 3600
print(diff)
which returns: 37.58784580333333 hours.
But this is the number of real hours between two dates. I want to know the number of specific business hours between two dates.
I can define two CustomBusinessHour objects with pandas to specify those business hours (which are 8AM to 4:30PM M-F, and 8AM to 12PM on Saturday, excluding US Federal holidays):
from pandas.tseries.offsets import CustomBusinessHour
from pandas.tseries.holiday import USFederalHolidayCalendar
business_hours_mtf = CustomBusinessHour(calendar=USFederalHolidayCalendar(), start='08:00', end='16:30')
business_hours_sat = CustomBusinessHour(calendar=USFederalHolidayCalendar(), start='08:00', end='12:00')
My understanding is that CustomBusinessHour is a type of pandas DateOffset object, so it should behave just like a relativedelta object. So I should be able to use it in the datetime arithmetic somehow, to get the number I want.
And that's as far as I was able to get.
What I think I'm struggling to understand is how relativedeltas work, and how to actually use them in datetime arithmetic.
Is this the right approach? If so, how can I use these CustomBusinessHour objects to get an accurate amount of elapsed business hours between the two dates?
I figured out a solution. It feels ugly and hacky, but it seems to work. Hopefully someone else has a simpler or more elegant solution.
Edit: I cleaned up the documentation a little bit to make it easier to read. Also added a missing kwarg in business_hours_sat. Figuring this out was a headache, so if anyone else has to deal with this problem, hopefully this solution helps.
from datetime import datetime, timedelta
from pandas.tseries.offsets import CustomBusinessHour
from pandas.tseries.holiday import USFederalHolidayCalendar
business_hours_mtf = CustomBusinessHour(calendar=USFederalHolidayCalendar(), start='08:00', end='16:30')
business_hours_sat = CustomBusinessHour(calendar=USFederalHolidayCalendar(), weekmask='Sat', start='08:00', end='12:00')
def get_business_hours_range(earlier_date: datetime, later_date: datetime) -> float:
"""Return the number of business hours between `earlier_date` and `later_date` as a float with two decimal places.
Algorithm:
1. Increment `earlier_date` by 1 "business hour" until it's further in the future than `later_date`.
2. Also increment an `elapsed_business_hours` variable by 1.
3. Once `earlier_date` is larger (further in the future) than `later_date`...
a. Roll back `earlier_date` by one business hour.
b. Get the close of business hour for `earlier_date` ([3a]).
c. Get the number of minutes between [3b] and [3a] (`minutes_remaining`).
d. Create a timedelta with `elapsed_business_hours` and `minutes_remaining`
e. Represent this timedelta as a float with two decimal places.
f. Return this float.
"""
# Count how many "business hours" have elapsed between the `earlier_date` and `later_date`.
elapsed_business_hours = 0.0
current_day_of_week = 0
while earlier_date < later_date:
day_of_week = earlier_date.isoweekday()
# 6 = Saturday
if day_of_week == 6:
# Increment `earlier_date` by one "business hour", as specified by the `business_hours_sat` CBH object.
earlier_date += business_hours_sat
# Increment the counter of how many "business hours" have elapsed between these two dates.
elapsed_business_hours += 1
# Save the current day of the week in `earlier_date`, in case this is the last iteration of this while loop.
current_day_of_week = day_of_week
# 1 = Monday, 2 = Tuesday, ...
elif day_of_week in (1, 2, 3, 4, 5):
# Increment `earlier_date` by one "business hour", as specified by the `business_hours_mtf` CBH object.
earlier_date += business_hours_mtf
# Increment the counter of how many "business hours" have elapsed between these two dates.
elapsed_business_hours += 1
# Save the current day of the week in `earlier_date`, in case this is the last iteration of this while loop.
current_day_of_week = day_of_week
# Once we've incremented `earlier_date` to a date further in the future than `later_date`, we know that we've counted
# all the full (60min) "business hours" between `earlier_date` and `later_date`. (We can only increment by one hour when using
# CBH, so when we make this final increment, we may be skipping over a few minutes in that last day.)
#
# So now we roll `earlier_date` back by 1 business hour, to the last full business hour before `later_date`. Then we get the
# close of business hour for that day, and subtract `earlier_date` from it. This will give us whatever minutes may be remaining
# in that day, that weren't accounted for when tallying the number of "business hours".
#
# But before we do these things, we need to check what day of the week the last business hour is, so we know which closing time
# to use.
if current_day_of_week == 6:
ed_rolled_back = earlier_date - business_hours_sat
ed_closing_time = datetime.combine(ed_rolled_back, business_hours_sat.end[0])
elif current_day_of_week in (1, 2, 3, 4, 5):
ed_rolled_back = earlier_date - business_hours_mtf
ed_closing_time = datetime.combine(ed_rolled_back, business_hours_mtf.end[0])
minutes_remaining = (ed_closing_time - ed_rolled_back).total_seconds() / 60
if 0 < minutes_remaining < 60:
delta = timedelta(hours=elapsed_business_hours, minutes=minutes_remaining)
else:
delta = timedelta(hours=elapsed_business_hours)
delta_hours = round(float(delta.total_seconds() / 3600), 2)
return delta_hours