In Python programming, the keyword `def` introduces a function definition. It signifies the beginning of a block of code that will execute only when the function is called. Following `def` is the function’s name, a parenthesized list of parameters (which can be empty), and a colon. The indented code that follows constitutes the function’s body. For example, `def greet(name):` initiates the definition of a function named `greet` that accepts one parameter, `name`.
The ability to define functions promotes code reusability and modularity. It allows developers to encapsulate specific tasks or operations into named blocks, which can then be invoked repeatedly throughout a program. This reduces code duplication, enhances readability, and simplifies maintenance. Historically, the concept of function definition has been fundamental to structured programming paradigms, enabling the decomposition of complex problems into smaller, more manageable units.
