A single file or many files containing functions, definitions, and variables created to perform certain tasks is called a module. It’s a .py extension file that can be imported at any given point and needs to be imported just once. A library is a collection of reusable functionality of code that’ll allow users to carry out a number of tasks without having to write the code. A Python library doesn’t have any specific use but refers to a collection of modules. This question is one of the most popular Python data science interview questions.