Extracting Frequency from Pandas BusinessHour Objects as Strings

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πŸ’‘ Problem Formulation: When working with time series data in Python’s Pandas library, you may come across a need to represent the frequency of a BusinessHour offset object as a string. For instance, if you have a BusinessHour object representing an 8-hour business day, you might want an output that articulates this as “8H”. How do we achieve this conversion? This article provides five methods to extract the frequency from a Pandas BusinessHour object and return it as a readable string.

Method 1: Using the freqstr Attribute

The BusinessHour class in Pandas has a freqstr attribute that returns the frequency string of the offset object. This attribute provides a concise way to obtain the frequency without additional processing.

Here’s an example:

from pandas.tseries.offsets import BusinessHour
bh = BusinessHour()
print(bh.freqstr)

Output:

'BH'

This snippet created a basic BusinessHour object with the default 9am to 5pm business hours and printed out the frequency string ‘BH’ using the freqstr attribute.

Method 2: Custom Function to Extract Frequency

For a customized frequency string, we can write a function that takes a BusinessHour object, and returns the frequency in a tailored string format based on our needs.

Here’s an example:

def get_freq_str(business_hour):
    return f"{business_hour.n}H"

bh = BusinessHour(8)
print(get_freq_str(bh))

Output:

'8H'

This code defines a function get_freq_str, which formats the number of hours in the BusinessHour object into a frequency string. We created a BusinessHour object for an 8-hour workday and used the function to get ‘8H’ as output.

Method 3: Overriding __str__ Method in a Subclass

Another approach is to subclass the BusinessHour class and override its __str__ method to return the frequency as a string formatted according to our requirements.

Here’s an example:

class CustomBusinessHour(BusinessHour):
    def __str__(self):
        return f"{self.n}H Business Hours"

bh = CustomBusinessHour(8)
print(str(bh))

Output:

'8H Business Hours'

Here we’ve created a subclass CustomBusinessHour and changed the __str__ method to return a more descriptive frequency string. When we print an instance of this subclass, it gives us a nicely formatted string.

Method 4: Using String Formatting with delta Property

The delta property of a BusinessHour object gives us a Timedelta that we can format into a string to represent the frequency.

Here’s an example:

bh = BusinessHour(8)
print(f"Frequency: {bh.delta.components.hours}H")

Output:

'Frequency: 8H'

The delta property refers to the time difference that the BusinessHour object represents. By accessing its component attributes, such as hours, we can format it into a custom frequency string.

Bonus One-Liner Method 5: Lambda Function

A succinct method for inline frequency string extraction is to use a lambda function for on-the-fly formatting.

Here’s an example:

format_freq = lambda bh: f"{bh.n}H"
print(format_freq(BusinessHour(8)))

Output:

'8H'

The lambda function format_freq takes a BusinessHour object as an argument and returns the formatted frequency. This method is quick and useful for inline execution without the need for defining a separate function.

Summary/Discussion

  • Method 1: Using the freqstr Attribute. Straightforward and built-in. Limited customization.
  • Method 2: Custom Function to Extract Frequency. Flexible and customizable. Requires additional function definition.
  • Method 3: Overriding __str__ Method in a Subclass. Useful for object-oriented designs. Overhead of subclassing.
  • Method 4: String Formatting with delta Property. Direct access to period details. Extra steps for formatting.
  • Method 5: Lambda Function. Quick and on-the-fly. Not as readable as a named function.