Python Distilled

5. Functions

Functions are a fundamental building block of most Python programs. This chapter describes function definitions, function application, scoping rules, closures, decorators, and other functional programming features. Particular attention is given to different programming idioms, evaluation models, and patterns associated with functions.

5.1 Function Definitions

Functions are defined with the def statement:

def add(x, y):
    return x + y

The first part of a function definition specifies the function name and parameter names that represent input values. The body of a function is a sequence of statements that execute when the function is called or applied. You apply a function to arguments by writing the function name followed by the arguments ...