Calculating the number of working days using Python

At times, we have a requirement to calculate the number of weekdays / working days between two dates.
Here's how you do it using Python:

	from datetime import date, timedelta
	start_date = date(2014, 07, 07)
	end_date = date(2014, 07, 23)
	all_days = [start_date + timedelta(days=x) for x in range((end_date-start_date).days + 1)]
	working_days = sum(1 for d in all_days if d.weekday() < 5)

view raw workingDaysUsingLoop.py hosted with ❤ by GitHub

But the above method involves usage of loops.
A more optimized way of doing it would be:

	from datetime import date, timedelta
	start_date = date(2014, 07, 07)
	end_date = date(2014, 07, 23)
	# Calculate number of days in starting and ending week
	start_week_days = min(start_date.weekday(), 4) + 1
	end_week_days = min(end_date.weekday(), 4) + 1
	# Calculate number of weeks between the dates
	no_of_weeks = end_date.isocalendar()[1] - start_date.isocalendar()[1]
	working_days = (5 * no_of_weeks) + end_week_days - start_week_days
	# include the starting day if it is weekday
	if start_date.weekday() < 5:
	working_days += 1

view raw workingDays.py hosted with ❤ by GitHub

In our project, we faced a requirement where given a start date, we had to calculate end date as start date + x working days.
Using the above logic, we can do:

	from datetime import date, timedelta
	def calculate_end_date(start_date):
	x = 45
	working_days = 0
	end_date = start_date + timedelta(days=x)
	while working_days < x:
	# Calculate number of days in starting and ending week
	start_week_days = min(start_date.weekday(), 4) + 1
	end_week_days = min(end_date.weekday(), 4) + 1
	# Calculate number of weeks between the dates
	no_of_weeks = ((end_date - datetime.timedelta(days=end_date.weekday()))
	- (start_date - datetime.timedelta(days=start_date.weekday()))).days / 7
	working_days = (5 * no_of_weeks) + end_week_days - start_week_days
	# include the starting day if it is weekday
	if start_date.weekday() < 5:
	working_days += 1
	# adjust the end date
	end_date = end_date + timedelta(days = x - working_days)
	return end_date

view raw calculateEndDate.py hosted with ❤ by GitHub

If you have a list of holidays to exclude, you could then do:

	from datetime import date, timedelta
	def calculate_end_date(start_date):
	x = 45
	working_days = 0
	end_date = start_date + timedelta(days=x)
	while working_days < x:
	# Calculate number of days in starting and ending week
	start_week_days = min(start_date.weekday(), 4) + 1
	end_week_days = min(end_date.weekday(), 4) + 1
	# Calculate number of weeks between the dates
	no_of_weeks = ((end_date - datetime.timedelta(days=end_date.weekday()))
	- (start_date - datetime.timedelta(days=start_date.weekday()))).days / 7
	working_days = (5 * no_of_weeks) + end_week_days - start_week_days
	# include the starting day if it is weekday
	if start_date.weekday() < 5:
	working_days += 1
	# adjust the end date
	end_date = end_date + timedelta(days = x - working_days)
	# Create your own list of holidays
	holidays = [date(2014, 01, 01), date(2014, 12, 25)]
	for day in holidays:
	if day >= start_date and day <= end_date:
	# Check if end date is Friday, then skip the weekend
	if end_date.weekday() == 4:
	end_date = end_date + timedelta(days=3)
	else:
	end_date = end_date + timedelta(days=1)
	return end_date

view raw calculateEndDateWithHolidays.py hosted with ❤ by GitHub