Functions in Python

Complete and in-depth guide to Python functions: creation, execution flow, parameters, closures, decorators, higher-order functions, callable objects, and advanced function behavior.

Function Basics & Execution Flow

Functions encapsulate reusable logic. Execution jumps into the function when called and returns back after completion.

Creating and Calling a Function

Define once, call many times.

Execution Flow Between Functions

Understand call stack behavior.

Parameters & Arguments

Python supports positional, keyword, default, variable-length, positional-only, and keyword-only parameters.

Default Parameters

Fallback values if argument is missing.

Keyword Arguments

Order-independent calling.

*args and **kwargs

Variable number of arguments.

Positional-only & Keyword-only Parameters

Advanced parameter control.

Type Hints & Annotations

Python allows optional type hints. They improve readability and tooling but are not enforced at runtime.

Basic Type Hints

Annotate parameters and return type.

First-Class Functions

In Python, functions are first-class objects. They can be stored, passed, and returned.

Assigning Function to Variable

Functions behave like objects.

Lambda Function

Small anonymous function.

Closures

A closure occurs when an inner function remembers variables from outer scope.

Stateful Closure

Maintain private state.

Decorators

Decorators wrap functions to extend or modify behavior.

Basic Decorator

Wrap function execution.

Higher Order Functions

A higher-order function accepts a function as argument or returns one.

Implementing map() Manually

Transform list elements.

Callable Objects

An object is callable if it can be called like a function using parentheses.

Using callable()

Check if object is callable.

Making Class Callable

Using __call__ method.

Immediately Invoked Functions (IIFE)

Python does not have a special IIFE syntax like JavaScript, but since functions are first-class objects, we can define and call them immediately using lambda expressions or by defining and calling them in the same block.

1. IIFE using lambda

Define and call an anonymous function instantly.

2. IIFE with Arguments

Pass arguments to the immediately invoked function.

3. Simulating IIFE using def

Define, execute, and remove function immediately.

4. When Should You Use IIFE?

Python philosophy on IIFE usage.