Here's a refactored version of your code:

Selecting the First Item in a Column After Grouping Using Pandas Transform and Masking

Converting a Year and Month Table into a Pandas Series in Python

Creating New Columns from Two Distinct Categorical Column Values in a Pandas DataFrame: A Comparison of Pivot Tables and Apply Functions

Data Manipulation with Pandas: Creating a New Column as Labels for Remaining Items

Working with Dates and Times in Python: A Comprehensive Guide

Removing Duplicates from a List in a Column of a Pandas DataFrame

Filtering Pandas DataFrames with 'in' and 'not in'

Splitting on a Specific Character in Python Strings

Identifying Column Names in a CSV File Based on Data