What is a module in Python?

A module in Python is indeed defined as a file that contains Python code, which can include the definition of functions, classes, and variables. This structure allows for better organization and modularization of code, making it easier to manage larger projects. By separating code into different modules, developers can compartmentalize functionality for easier testing, debugging, and reuse.

When a module is imported into another Python script, its functions and classes become available for use, promoting code reuse and efficiency. This concept is fundamental in Python programming as it supports the modular programming paradigm, enabling developers to write clean and maintainable code.

The other options do not accurately represent what a module is. A built-in function refers to pre-defined functions provided by Python but does not embody the entire concept of a module. A type of data structure pertains to the way data is organized and stored in Python, which is unrelated to the definition of a module. A method for manipulating strings specifies operations on string data types, which is a specific functionality, rather than the overarching concept of a module as a collection of code.