Understanding Pandas DataFrames with Regular Expressions for Advanced Filtering

Multiplying All Columns Next to Each Other in a Pandas DataFrame Using Groupby with Floor Division

Grouping and Conditional Selection in Pandas DataFrames for Efficient Data Analysis

Implementing the Composition Pattern in Python: Redirecting Methods of a Contained Class

Optimizing Dictionary of Lists for Efficient Lookups: A Performance Boost with Precomputed Minimum Values

Looping over Pandas Columns for Generating Histograms with Matplotlib

Handling Unequal Inner Levels in MultiIndex DataFrames: A Step-by-Step Guide to Reindexing and Padding

Understanding Pandas Drop Functionality: Mastering the Art of Efficient Data Manipulation

To calculate the sum of sales for each salesman in a month before their training date, we need to group by "salesman" and "transaction_month", then apply the aggregation function `sum` to the 'sales' column.

Unpacking Nested Dictionary Structures in Pandas DataFrames: A Comparative Analysis of Two Approaches