pandas User Guide, The pandas development team, 2023 - The official documentation for pandas, covering essential functionalities, data structures, and various methods for data manipulation including direct assignment, apply(), replace(), map(), string methods, and type conversions.
Python for Data Analysis, Wes McKinney, 2022 (O'Reilly Media) - An authoritative guide by the creator of pandas, providing extensive explanations and practical examples for data wrangling and manipulation with pandas, directly relevant to modifying existing columns.
Broadcasting, The NumPy community, 2023 - Explains the fundamental concept of broadcasting in NumPy, which is the mechanism behind efficient vectorized operations that Pandas leverages for element-wise column modifications.