Working with Business Days and Holidays in Pandas: Exploring Alternatives to `CustomBusinessDay.holidays`

CustomBusinessDay Offset

In Pandas, the CustomBusinessDay offset allows you to create custom business day objects for date manipulation. It's a subclass of DateOffset and provides more flexibility compared to standard business day offsets like BDay.

holidays Parameter

The holidays parameter within CustomBusinessDay is a key element for defining custom business days. It takes a list of holidays (represented as datetime objects) that you want to exclude when calculating offsets. This enables you to:

• Create Custom Business Calendars
  By specifying holidays along with a custom weekmask (optional parameter defining valid weekdays), you can establish your own business day calendar that deviates from the standard Monday-to-Friday week.
• Skip Specific Holidays
  When adding or subtracting business days, dates falling on these holidays will be bypassed.

Example

import pandas as pd

# Define holidays (replace with your actual holidays)
holidays = pd.to_datetime(['2024-01-01', '2024-07-04'])  # New Year's Day and Independence Day

# Create a custom business day offset that skips these holidays
custom_business_day = pd.tseries.offsets.CustomBusinessDay(holidays=holidays)

# Starting date (replace with your date)
start_date = pd.to_datetime('2024-06-10')

# Add 5 business days, excluding holidays
new_date = start_date + 5 * custom_business_day

print(new_date)  # Output: 2024-06-17 (assuming no other holidays between)

In this example, adding 5 business days using custom_business_day will skip New Year's Day (January 1st) and Independence Day (July 4th), resulting in June 17th, 2024 (assuming there are no other holidays within that period).

• CustomBusinessDay offers greater control over how business days are calculated in your Pandas operations.
• Combine holidays with a custom weekmask (optional) to define a completely customized business calendar.
• Use holidays as a list of datetime objects representing dates to exclude as business days.

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Skipping Multiple Holidays and Weekends

import pandas as pd

# Define holidays
holidays = pd.to_datetime(['2024-01-01', '2024-07-04', '2024-12-25'])  # Add Christmas

# Consider only weekdays (Monday-Friday) as business days
custom_business_day = pd.tseries.offsets.CustomBusinessDay(holidays=holidays, weekmask='Mon Tue Wed Thu Fri')

# Starting date
start_date = pd.to_datetime('2024-06-08')  # A Saturday

# Add 10 business days
new_date = start_date + 10 * custom_business_day

print(new_date)  # Output: 2024-06-24 (skips holidays and weekends)

In this example, we add Christmas to the holidays list and define the weekmask to include only weekdays. This ensures that Saturdays and Sundays, along with the specified holidays, are excluded when calculating business days.

Creating a Shortened Business Week

import pandas import as pd

# Define holidays
holidays = pd.to_datetime(['2024-01-01', '2024-07-04'])

# Consider Tuesday, Wednesday, and Thursday as business days
custom_business_day = pd.tseries.offsets.CustomBusinessDay(holidays=holidays, weekmask='Tue Wed Thu')

# Starting date
start_date = pd.to_datetime('2024-06-10')

# Add 3 business days
new_date = start_date + 3 * custom_business_day

print(new_date)  # Output: 2024-06-13 (skips holidays and non-business weekdays)

This example demonstrates defining a shortened business week that only includes Tuesday, Wednesday, and Thursday. Holidays are still excluded as well.

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Pre-defined Holiday Calendars

• Pandas provides built-in holiday calendars like USFederalHolidayCalendar that cover common holidays in specific regions. You can use these calendars with CustomBusinessDay for a quicker setup:

from pandas.tseries.holiday import USFederalHolidayCalendar
from pandas.tseries.offsets import CustomBusinessDay

holidays = USFederalHolidayCalendar().holidays(start=start_date, end=end_date)
custom_business_day = CustomBusinessDay(holidays=holidays)

# Use custom_business_day for date manipulation

BDay Offset with Manual Holiday Exclusion

• If you have a limited number of holidays, you can use the standard BDay offset for business days and manually exclude the holidays in your calculations.

import pandas as pd

def add_business_days(start_date, num_days, holidays):
  new_date = start_date
  for _ in range(num_days):
    new_date += pd.offsets.BDay(1)
    while new_date.to_pydatetime() in holidays:
      new_date += pd.offsets.BDay(1)
  return new_date

# Example usage
holidays = pd.to_datetime(['2024-01-01', '2024-07-04'])
new_date = add_business_days(start_date, 5, holidays)

External Holiday Data Sources

Choosing the Right Alternative

The best alternative depends on your specific needs:

• External libraries
  Ideal for handling complex holiday schedules or integrating with external holiday data sources.
• Manual exclusion
  Suitable for a small number of holidays.
• Pre-defined calendars
  Use them if your holidays align with standard calendars (e.g., US holidays).