Functions in Python

Functions are reusable blocks of code. Use the `def` keyword to define them. Functions can have parameters, return values, and documentation strings.

Python functions support various parameter types: positional, keyword, default, variable-length, and keyword-only arguments.

Lambda functions are anonymous, single-expression functions created with the `lambda` keyword. They're useful for short, simple operations.

Decorators are functions that modify the behavior of other functions. They're a powerful feature for adding functionality like logging, timing, access control, and caching.

Closures are functions that capture variables from their enclosing scope. Understanding scopes (local, enclosing, global, built-in) is crucial.

Generator functions use `yield` to produce a sequence of values lazily. They're memory-efficient for large sequences.

Modern Python patterns including functools, partial functions, and functional programming techniques.

Important guidelines, patterns, and common mistakes to avoid when working with functions.