Python Pandas: Rolling Dates Forward with Custom Business Hours

💡 Problem Formulation: When using Python’s pandas library, a common task is to manipulate datetime entities. Specifically, for business analysis, it may be critical to roll a provided date forward to the next valid business offset only if the date is not already on a valid offset. For instance, if we provide 2023-04-01 15:00:00 on a weekday schedule with custom business hours, we’d want to find the next business hour if this time is outside those specified hours (e.g., desired output could be 2023-04-03 09:00:00 if the next business day starts at 9 AM).

Method 1: Using pandas CustomBusinessHour

An effective means to roll a provided date forward in the context of custom business hours is to use pandas’ CustomBusinessHour. The CustomBusinessHour can be tailored to suit bespoke needs, such as accounting for weekends, holidays, and specific working hours. It’s a flexible method that allows developers to define custom offsets, providing great control over date manipulation.

Here’s an example:

from pandas.tseries.offsets import CustomBusinessHour
from pandas import Timestamp

custom_business_hour = CustomBusinessHour(start='09:00', end='17:00')
provided_date = Timestamp('2023-04-01 15:00:00')

if not custom_business_hour.onOffset(provided_date):
    next_business_offset = provided_date + custom_business_hour
else:
    next_business_offset = provided_date

print(next_business_offset)

Output:

2023-04-03 09:00:00

This code snippet creates a CustomBusinessHour offset that defines a business day to start at 9 AM and end at 5 PM. Given a date, the onOffset method checks if it’s already on a valid offset. If it’s not, the date is rolled forward to the next valid business hour.

Method 2: Using the rollforward() Method

The rollforward() method provided by the pandas CustomBusinessHour class offers a simple way to move a date forward to the next available business hour. This method is not as widely used as other methods but still serves well when dealing with very specific business calendars.

Here’s an example:

from pandas.tseries.offsets import CustomBusinessHour
from pandas import Timestamp

custom_business_hour = CustomBusinessHour(start='09:00', end='17:00')
provided_date = Timestamp('2023-04-01 15:00:00')
next_business_offset = custom_business_hour.rollforward(provided_date)

print(next_business_offset)

Output:

2023-04-03 09:00:00

This code demonstrates the rollforward() method that moves the provided date to the next business hour. Unlike the previous method, you don’t need to check whether the date is already on an offset or not, simplifying the code.

Method 3: Defining a Custom Function

Creating a custom function that incorporates the CustomBusinessHour logic allows more sophisticated control and potential reuse. It can encapsulate logic for rolling dates forward and may be integrated with additional business logic as necessary.

Here’s an example:

from pandas.tseries.offsets import CustomBusinessHour
from pandas import Timestamp

def to_next_business_hour(provided_date, start='09:00', end='17:00'):
    custom_business_hour = CustomBusinessHour(start=start, end=end)
    if not custom_business_hour.onOffset(provided_date):
        return provided_date + custom_business_hour
    return provided_date

provided_date = Timestamp('2023-04-01 15:00:00')
next_business_offset = to_next_business_hour(provided_date)

print(next_business_offset)

Output:

2023-04-03 09:00:00

This snippet creates a custom function to_next_business_hour which, when provided with a date and custom business hours, returns the next business hour date accordingly. This method abstracts the logic and makes it easily reusable.

Method 4: Extending pandas with a Custom Class

For projects that frequently manipulate business hour offsets, extending pandas with a custom class can be advantageous. Building a custom class that inherits from pandas’ classes might encapsulate specific behavior and can be convenient and clear when dealing with such transformations regularly.

Here’s an example:

from pandas.tseries.offsets import CustomBusinessHour
from pandas import Timestamp

class CustomBusinessHourScheduler:
    def __init__(self, start='09:00', end='17:00'):
        self.custom_business_hour = CustomBusinessHour(start=start, end=end)

    def get_next_business_hour(self, dt):
        if not self.custom_business_hour.onOffset(dt):
            return dt + self.custom_business_hour
        return dt

scheduler = CustomBusinessHourScheduler()
provided_date = Timestamp('2023-04-01 15:00:00')
next_business_offset = scheduler.get_next_business_hour(provided_date)

print(next_business_offset)

Output:

2023-04-03 09:00:00

The code above defines a new class CustomBusinessHourScheduler which wraps the custom business hour functionality. It provides a method to get the next business hour from a provided date. This method promotes code organization and object-oriented practices.

Bonus One-Liner Method 5: Using a Lambda Function

Lambda functions in Python allow for writing concise, one-line functions. These can be particularly useful for inline operations or simple transformations such as rolling business hours forward.

Here’s an example:

from pandas.tseries.offsets import CustomBusinessHour
from pandas import Timestamp

cbh = CustomBusinessHour(start='09:00', end='17:00')
provided_date = Timestamp('2023-04-01 15:00:00')
next_business_offset = (lambda x: x + cbh if not cbh.onOffset(x) else x)(provided_date)

print(next_business_offset)

Output:

2023-04-03 09:00:00

This one-liner uses a lambda function to apply the CustomBusinessHour logic. The function takes a date x and returns it modified if it’s not already on a business hour offset. For simple transformations, this method is quick and easy to read.

Summary/Discussion

• Method 1: CustomBusinessHour. Offers a great deal of flexibility and good for more complex calendar logic. However, it requires additional checks and may result in slightly more verbose code.
• Method 2: Rollforward Method. Simplifies the process, as it doesn’t need an explicit check for the current offset. But it assumes that the rollforward behavior is always the desired action.
• Method 3: Custom Function. Provides encapsulation and reusability, which is great for larger codebases. It does add an extra layer of abstraction.
• Method 4: Custom Class Extension. Ideal for applications that deal extensively with business hour calculations, promoting modular and maintainable code. It’s a bit overkill for simple, one-off operations.
• Method 5: Lambda Function. Quick and concise. It’s perfect for inline transformations but can be less readable and not as reusable as other methods.